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PROC(5)			   Linux Programmer's Manual		       PROC(5)

       proc - process information pseudo-file system

       The proc file system is a pseudo-file system which is used as an inter‐
       face to kernel data structures.	It is commonly mounted at /proc.  Most
       of  it  is  read-only,  but  some  files	 allow	kernel variables to be

       The following outline gives a quick tour through the /proc hierarchy.

	      There is a numerical subdirectory for each running process;  the
	      subdirectory is named by the process ID.	Each such subdirectory
	      contains the following pseudo-files and directories.

       /proc/[pid]/auxv (since 2.6.0-test7)
	      This contains the contents of the	 ELF  interpreter  information
	      passed  to the process at exec time.  The format is one unsigned
	      long ID plus one unsigned long value for each entry.   The  last
	      entry contains two zeros.

	      This holds the complete command line for the process, unless the
	      process is a zombie.  In the latter case, there  is  nothing  in
	      this  file:  that	 is, a read on this file will return 0 charac‐
	      ters.  The command-line arguments appear in this file as	a  set
	      of null-separated strings, with a further null byte ('\0') after
	      the last string.

       /proc/[pid]/coredump_filter (since kernel 2.6.23)
	      See core(5).

       /proc/[pid]/cpuset (since kernel 2.6.12)
	      See cpuset(7).

	      This is a symbolic link to the current working directory of  the
	      process.	 To  find out the current working directory of process
	      20, for instance, you can do this:

		  $ cd /proc/20/cwd; /bin/pwd

	      Note that the pwd command is often a shell built-in,  and	 might
	      not work properly.  In bash(1), you may use pwd -P.

	      In  a  multithreaded process, the contents of this symbolic link
	      are not available if the	main  thread  has  already  terminated
	      (typically by calling pthread_exit(3)).

	      This file contains the environment for the process.  The entries
	      are separated by null bytes ('\0'), and there may be a null byte
	      at  the  end.   Thus, to print out the environment of process 1,
	      you would do:

		  $ (cat /proc/1/environ; echo) | tr '\000' '\n'

	      Under Linux 2.2 and later, this file is a symbolic link contain‐
	      ing  the actual pathname of the executed command.	 This symbolic
	      link can be dereferenced normally; attempting to	open  it  will
	      open  the	 executable.  You can even type /proc/[pid]/exe to run
	      another copy of the same executable as is being run  by  process
	      [pid].   In  a  multithreaded process, the contents of this sym‐
	      bolic link are not available if the main thread has already ter‐
	      minated (typically by calling pthread_exit(3)).

	      Under  Linux 2.0 and earlier /proc/[pid]/exe is a pointer to the
	      binary which was executed, and appears as a  symbolic  link.   A
	      readlink(2)  call	 on this file under Linux 2.0 returns a string
	      in the format:


	      For example, [0301]:1502 would be inode 1502 on device major  03
	      (IDE,  MFM,  etc. drives) minor 01 (first partition on the first

	      find(1) with the -inum option can be used to locate the file.

	      This is a subdirectory containing one entry for each file	 which
	      the process has open, named by its file descriptor, and which is
	      a symbolic link to the actual file.  Thus, 0 is standard	input,
	      1 standard output, 2 standard error, etc.

	      In  a  multithreaded process, the contents of this directory are
	      not available if the main thread has already  terminated	(typi‐
	      cally by calling pthread_exit(3)).

	      Programs	that  will take a filename as a command-line argument,
	      but will not take input from standard input if  no  argument  is
	      supplied,	 or that write to a file named as a command-line argu‐
	      ment, but will not send their output to standard	output	if  no
	      argument	is  supplied, can nevertheless be made to use standard
	      input or standard out using /proc/[pid]/fd.  For example, assum‐
	      ing  that -i is the flag designating an input file and -o is the
	      flag designating an output file:

		  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...

	      and you have a working filter.

	      /proc/self/fd/N is approximately the same as /dev/fd/N  in  some
	      Unix and Unix-like systems.  Most Linux MAKEDEV scripts symboli‐
	      cally link /dev/fd to /proc/self/fd, in fact.

	      Most systems provide symbolic links /dev/stdin, /dev/stdout, and
	      /dev/stderr, which respectively link to the files 0, 1, and 2 in
	      /proc/self/fd.  Thus the example command above could be  written

		  $ foobar -i /dev/stdin -o /dev/stdout ...

       /proc/[pid]/fdinfo/ (since kernel 2.6.22)
	      This  is a subdirectory containing one entry for each file which
	      the process has open, named by its file  descriptor.   The  con‐
	      tents  of	 each file can be read to obtain information about the
	      corresponding file descriptor, for example:

		  $ cat /proc/12015/fdinfo/4
		  pos:	  1000
		  flags:  01002002

	      The pos field is a decimal number showing the current file  off‐
	      set.   The flags field is an octal number that displays the file
	      access mode and file status flags (see open(2)).

	      The files in this directory are readable only by	the  owner  of
	      the process.

       /proc/[pid]/limits (since kernel 2.6.24)
	      This file displays the soft limit, hard limit, and units of mea‐
	      surement for each of the process's resource  limits  (see	 getr‐
	      limit(2)).   The	file is protected to only allow reading by the
	      real UID of the process.

	      A file containing the currently mapped memory regions and	 their
	      access permissions.

	      The format is:

	      address		perms offset  dev   inode   pathname
	      08048000-08056000 r-xp 00000000 03:0c 64593   /usr/sbin/gpm
	      08056000-08058000 rw-p 0000d000 03:0c 64593   /usr/sbin/gpm
	      08058000-0805b000 rwxp 00000000 00:00 0
	      40000000-40013000 r-xp 00000000 03:0c 4165    /lib/
	      40013000-40015000 rw-p 00012000 03:0c 4165    /lib/
	      4001f000-40135000 r-xp 00000000 03:0c 45494   /lib/
	      40135000-4013e000 rw-p 00115000 03:0c 45494   /lib/
	      4013e000-40142000 rw-p 00000000 00:00 0
	      bffff000-c0000000 rwxp 00000000 00:00 0

	      where  "address"	is  the	 address  space in the process that it
	      occupies, "perms" is a set of permissions:

		   r = read
		   w = write
		   x = execute
		   s = shared
		   p = private (copy on write)

	      "offset" is the offset into  the	file/whatever,	"dev"  is  the
	      device  (major:minor),  and "inode" is the inode on that device.
	      0 indicates that no inode is associated with the memory  region,
	      as the case would be with BSS (uninitialized data).

	      Under Linux 2.0 there is no field giving pathname.

	      This  file can be used to access the pages of a process's memory
	      through open(2), read(2), and lseek(2).

       /proc/[pid]/mountinfo (since Linux 2.6.26)
	      This file contains information about mount points.  It  contains
	      lines of the form:

	      36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
	      (1)(2)(3)	  (4)	(5)	 (6)	  (7)	(8) (9)	  (10)	       (11)

	      The  numbers  in	parentheses  are  labels  for the descriptions

	      (1)  mount ID: unique identifier of the  mount  (may  be	reused
		   after umount(2)).

	      (2)  parent  ID:	ID  of parent mount (or of self for the top of
		   the mount tree).

	      (3)  major:minor: value of st_dev for files on file system  (see

	      (4)  root: root of the mount within the file system.

	      (5)  mount point: mount point relative to the process's root.

	      (6)  mount options: per-mount options.

	      (7)  optional   fields:	zero   or  more	 fields	 of  the  form

	      (8)  separator: marks the end of the optional fields.

	      (9)  file	 system	 type:	name  of  file	system	in  the	  form

	      (10) mount source: file system-specific information or "none".

	      (11) super options: per-super block options.

	      Parsers  should  ignore  all unrecognized optional fields.  Cur‐
	      rently the possible optional fields are:

		   shared:X	     mount is shared in peer group X

		   master:X	     mount is slave to peer group X

		   propagate_from:X  mount is slave and	 receives  propagation
				     from peer group X (*)

		   unbindable	     mount is unbindable

	      (*)  X  is  the  closest dominant peer group under the process's
	      root.  If X is the immediate master of the mount, or if there is
	      no  dominant peer group under the same root, then only the "mas‐
	      ter:X" field is present and not the "propagate_from:X" field.

	      For  more	 information  on  mount	 propagation  see:  Documenta‐
	      tion/filesystems/sharedsubtree.txt in the kernel source tree.

       /proc/[pid]/mounts (since Linux 2.4.19)
	      This  is a list of all the file systems currently mounted in the
	      process's mount namespace.  The format of	 this  file  is	 docu‐
	      mented  in  fstab(5).  Since kernel version 2.6.15, this file is
	      pollable: after opening the file for reading, a change  in  this
	      file  (i.e., a file system mount or unmount) causes select(2) to
	      mark  the	 file  descriptor  as  readable,   and	 poll(2)   and
	      epoll_wait(2) mark the file as having an error condition.

       /proc/[pid]/mountstats (since Linux 2.6.17)
	      This  file exports information (statistics, configuration infor‐
	      mation) about the mount points  in  the  process's  name	space.
	      Lines in this file have the form:

	      device /dev/sda7 mounted on /home with fstype ext3 [statistics]
	      (	      1	     )		  ( 2 )		    (3 ) (4)

	      The fields in each line are:

	      (1)  The	name  of the mounted device (or "nodevice" if there is
		   no corresponding device).

	      (2)  The mount point within the file system tree.

	      (3)  The file system type.

	      (4)  Optional statistics and  configuration  information.	  Cur‐
		   rently  (as	at Linux 2.6.26), only NFS file systems export
		   information via this field.

	      This file is only readable by the owner of the process.

       /proc/[pid]/numa_maps (since Linux 2.6.14)
	      See numa(7).

       /proc/[pid]/oom_adj (since Linux 2.6.11)
	      This file can be used to adjust the score used to	 select	 which
	      process  should  be  killed in an out-of-memory (OOM) situation.
	      The kernel uses this value for  a	 bit-shift  operation  of  the
	      process's	 oom_score value: valid values are in the range -16 to
	      +15, plus the special  value  -17,  which	 disables  OOM-killing
	      altogether  for  this  process.	A positive score increases the
	      likelihood of this process being killed  by  the	OOM-killer;  a
	      negative score decreases the likelihood.

	      The default value for this file is 0; a new process inherits its
	      parent's	oom_adj	 setting.   A  process	must   be   privileged
	      (CAP_SYS_RESOURCE) to update this file.

	      Since  Linux  2.6.36, use of this file is deprecated in favor of

       /proc/[pid]/oom_score (since Linux 2.6.11)
	      This file displays the current score that the  kernel  gives  to
	      this process for the purpose of selecting a process for the OOM-
	      killer.  A higher score means that the process is more likely to
	      be  selected by the OOM-killer.  The basis for this score is the
	      amount of memory used by the  process,  with  increases  (+)  or
	      decreases (-) for factors including:

	      * whether	 the  process  creates a lot of children using fork(2)

	      * whether the process has been running a long time, or has  used
		a lot of CPU time (-);

	      * whether the process has a low nice value (i.e., > 0) (+);

	      * whether the process is privileged (-); and

	      * whether the process is making direct hardware access (-).

	      The  oom_score  also  reflects  the  adjustment specified by the
	      oom_score_adj or oom_adj setting for the process.

	      This file can be used to adjust the badness  heuristic  used  to
	      select which process gets killed in out-of-memory conditions.

	      The  badness  heuristic  assigns	a value to each candidate task
	      ranging from 0 (never kill) to 1000 (always kill)	 to  determine
	      which  process  is targeted.  The units are roughly a proportion
	      along that range of allowed  memory  the	process	 may  allocate
	      from, based on an estimation of its current memory and swap use.
	      For example, if a task is using all allowed memory, its  badness
	      score  will be 1000.  If it is using half of its allowed memory,
	      its score will be 500.

	      There is an additional factor included  in  the  badness	score:
	      root processes are given 3% extra memory over other tasks.

	      The  amount  of "allowed" memory depends on the context in which
	      the OOM-killer was called.  If it is due to the memory  assigned
	      to  the  allocating  task's  cpuset being exhausted, the allowed
	      memory represents the set of mems assigned to that  cpuset  (see
	      cpuset(7)).   If	it  is	due  to	 a  mempolicy's	 node(s) being
	      exhausted, the allowed memory represents the  set	 of  mempolicy
	      nodes.   If  it  is  due to a memory limit (or swap limit) being
	      reached, the allowed memory is that configured limit.   Finally,
	      if  it  is  due  to  the	entire system being out of memory, the
	      allowed memory represents all allocatable resources.

	      The value of oom_score_adj is added to the badness score	before
	      it  is  used to determine which task to kill.  Acceptable values
	      range    from	-1000	  (OOM_SCORE_ADJ_MIN)	  to	 +1000
	      (OOM_SCORE_ADJ_MAX).   This  allows  user	 space	to control the
	      preference for OOM-killing, ranging  from	 always	 preferring  a
	      certain  task  or completely disabling it from OOM-killing.  The
	      lowest possible value, -1000, is equivalent  to  disabling  OOM-
	      killing  entirely	 for  that task, since it will always report a
	      badness score of 0.

	      Consequently, it is very simple for user	space  to  define  the
	      amount   of  memory  to  consider	 for  each  task.   Setting  a
	      oom_score_adj value of +500, for example, is roughly  equivalent
	      to  allowing  the	 remainder  of	tasks sharing the same system,
	      cpuset, mempolicy, or memory  controller	resources  to  use  at
	      least  50%  more	memory.	  A  value of -500, on the other hand,
	      would be roughly equivalent to discounting  50%  of  the	task's
	      allowed  memory  from  being  considered	as scoring against the

	      For    backward	 compatibility	  with	  previous    kernels,
	      /proc/[pid]/oom_adj can still be used to tune the badness score.
	      Its value is scaled linearly with oom_score_adj.

	      Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will
	      change the other with its scaled value.

	      Unix  and	 Linux	support	 the idea of a per-process root of the
	      file system, set by the chroot(2) system call.  This file	 is  a
	      symbolic	link  that points to the process's root directory, and
	      behaves as exe, fd/*, etc. do.

	      In a multithreaded process, the contents of this	symbolic  link
	      are  not	available  if  the  main thread has already terminated
	      (typically by calling pthread_exit(3)).

       /proc/[pid]/smaps (since Linux 2.6.14)
	      This file shows memory consumption for  each  of	the  process's
	      mappings.	  For each of mappings there is a series of lines such
	      as the following:

		  08048000-080bc000 r-xp 00000000 03:02 13130	   /bin/bash
		  Size:		      464 kB
		  Rss:		      424 kB
		  Shared_Clean:	      424 kB
		  Shared_Dirty:		0 kB
		  Private_Clean:	0 kB
		  Private_Dirty:	0 kB

	      The first of these lines shows the same information as  is  dis‐
	      played for the mapping in /proc/[pid]/maps.  The remaining lines
	      show the size of the mapping, the amount of the mapping that  is
	      currently	 resident in RAM, the number of clean and dirty shared
	      pages in the mapping, and the number of clean and dirty  private
	      pages in the mapping.

	      This file is only present if the CONFIG_MMU kernel configuration
	      option is enabled.

	      Status information about the process.  This is  used  by	ps(1).
	      It is defined in /usr/src/linux/fs/proc/array.c.

	      The  fields,  in order, with their proper scanf(3) format speci‐
	      fiers, are:

	      pid %d	  The process ID.

	      comm %s	  The filename	of  the	 executable,  in  parentheses.
			  This	is  visible  whether  or not the executable is
			  swapped out.

	      state %c	  One character from the string "RSDZTW"  where	 R  is
			  running,  S  is sleeping in an interruptible wait, D
			  is waiting in uninterruptible disk sleep, Z is  zom‐
			  bie,	T is traced or stopped (on a signal), and W is

	      ppid %d	  The PID of the parent.

	      pgrp %d	  The process group ID of the process.

	      session %d  The session ID of the process.

	      tty_nr %d	  The controlling terminal of the process.  (The minor
			  device  number  is  contained	 in the combination of
			  bits 31 to 20 and 7 to 0; the major device number is
			  in bits 15 t0 8.)

	      tpgid %d	  The  ID  of the foreground process group of the con‐
			  trolling terminal of the process.

	      flags %u (%lu before Linux 2.6.22)
			  The kernel flags word of the process.	 For bit mean‐
			  ings,	 see  the  PF_*	 defines  in  <linux/sched.h>.
			  Details depend on the kernel version.

	      minflt %lu  The number of minor  faults  the  process  has  made
			  which	 have  not required loading a memory page from

	      cminflt %lu The  number  of  minor  faults  that	the  process's
			  waited-for children have made.

	      majflt %lu  The  number  of  major  faults  the process has made
			  which have required loading a memory page from disk.

	      cmajflt %lu The  number  of  major  faults  that	the  process's
			  waited-for children have made.

	      utime %lu	  Amount  of time that this process has been scheduled
			  in user mode, measured in  clock  ticks  (divide  by
			  sysconf(_SC_CLK_TCK).	  This	includes  guest	 time,
			  guest_time (time spent running a  virtual  CPU,  see
			  below),  so  that applications that are not aware of
			  the guest time field do  not	lose  that  time  from
			  their calculations.

	      stime %lu	  Amount  of time that this process has been scheduled
			  in kernel mode, measured in clock ticks  (divide  by

	      cutime %ld  Amount  of time that this process's waited-for chil‐
			  dren have been scheduled in user mode,  measured  in
			  clock	 ticks	(divide by sysconf(_SC_CLK_TCK).  (See
			  also	 times(2).)    This   includes	 guest	 time,
			  cguest_time  (time  spent running a virtual CPU, see

	      cstime %ld  Amount of time that this process's waited-for	 chil‐
			  dren have been scheduled in kernel mode, measured in
			  clock ticks (divide by sysconf(_SC_CLK_TCK).

	      priority %ld
			  (Explanation for Linux 2.6) For processes running  a
			  real-time   scheduling  policy  (policy  below;  see
			  sched_setscheduler(2)), this is the negated schedul‐
			  ing  priority,  minus	 one; that is, a number in the
			  range -2 to -100, corresponding to real-time priori‐
			  ties	1  to  99.  For processes running under a non-
			  real-time scheduling policy, this is	the  raw  nice
			  value (setpriority(2)) as represented in the kernel.
			  The kernel stores nice  values  as  numbers  in  the
			  range	 0  (high)  to	39 (low), corresponding to the
			  user-visible nice range of -20 to 19.

			  Before Linux 2.6, this was a scaled value  based  on
			  the scheduler weighting given to this process.

	      nice %ld	  The  nice value (see setpriority(2)), a value in the
			  range 19 (low priority) to -20 (high priority).

	      num_threads %ld
			  Number of threads in this process (since Linux 2.6).
			  Before kernel 2.6, this field was hard coded to 0 as
			  a placeholder for an earlier removed field.

	      itrealvalue %ld
			  The time in jiffies before the next SIGALRM is  sent
			  to the process due to an interval timer.  Since ker‐
			  nel 2.6.17, this field is no longer maintained,  and
			  is hard coded as 0.

	      starttime %llu (was %lu before Linux 2.6)
			  The time in jiffies the process started after system

	      vsize %lu	  Virtual memory size in bytes.

	      rss %ld	  Resident Set Size: number of pages the  process  has
			  in  real memory.  This is just the pages which count
			  towards text, data, or stack space.  This  does  not
			  include  pages which have not been demand-loaded in,
			  or which are swapped out.

	      rsslim %lu  Current soft limit  in  bytes	 on  the  rss  of  the
			  process;  see	 the description of RLIMIT_RSS in get‐

	      startcode %lu
			  The address above which program text can run.

	      endcode %lu The address below which program text can run.

	      startstack %lu
			  The address of  the  start  (i.e.,  bottom)  of  the

	      kstkesp %lu The  current	value of ESP (stack pointer), as found
			  in the kernel stack page for the process.

	      kstkeip %lu The current EIP (instruction pointer).

	      signal %lu  The bitmap of pending signals, displayed as a	 deci‐
			  mal  number.	 Obsolete, because it does not provide
			  information	 on	real-time     signals;	   use
			  /proc/[pid]/status instead.

	      blocked %lu The  bitmap of blocked signals, displayed as a deci‐
			  mal number.  Obsolete, because it does  not  provide
			  information	  on	 real-time     signals;	   use
			  /proc/[pid]/status instead.

	      sigignore %lu
			  The bitmap of ignored signals, displayed as a	 deci‐
			  mal  number.	 Obsolete, because it does not provide
			  information	 on	real-time     signals;	   use
			  /proc/[pid]/status instead.

	      sigcatch %lu
			  The bitmap of caught signals, displayed as a decimal
			  number.   Obsolete,  because	it  does  not  provide
			  information	  on	 real-time     signals;	   use
			  /proc/[pid]/status instead.

	      wchan %lu	  This is the "channel" in which the process is	 wait‐
			  ing.	It is the address of a system call, and can be
			  looked up in a namelist if you need a textual	 name.
			  (If you have an up-to-date /etc/psdatabase, then try
			  ps -l to see the WCHAN field in action.)

	      nswap %lu	  Number of pages swapped (not maintained).

	      cnswap %lu  Cumulative nswap  for	 child	processes  (not	 main‐

	      exit_signal %d (since Linux 2.1.22)
			  Signal to be sent to parent when we die.

	      processor %d (since Linux 2.2.8)
			  CPU number last executed on.

	      rt_priority %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
			  Real-time scheduling priority, a number in the range
			  1 to 99 for processes scheduled  under  a  real-time
			  policy,  or  0,  for	non-real-time  processes  (see

	      policy %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
			  Scheduling   policy	(see   sched_setscheduler(2)).
			  Decode using the SCHED_* constants in linux/sched.h.

	      delayacct_blkio_ticks %llu (since Linux 2.6.18)
			  Aggregated block I/O delays, measured in clock ticks

	      guest_time %lu (since Linux 2.6.24)
			  Guest time of the process (time spent running a vir‐
			  tual	CPU for a guest operating system), measured in
			  clock ticks (divide by sysconf(_SC_CLK_TCK).

	      cguest_time %ld (since Linux 2.6.24)
			  Guest time of the process's  children,  measured  in
			  clock ticks (divide by sysconf(_SC_CLK_TCK).

	      Provides information about memory usage, measured in pages.  The
	      columns are:

		  size	     total program size
			     (same as VmSize in /proc/[pid]/status)
		  resident   resident set size
			     (same as VmRSS in /proc/[pid]/status)
		  share	     shared pages (from shared mappings)
		  text	     text (code)
		  lib	     library (unused in Linux 2.6)
		  data	     data + stack
		  dt	     dirty pages (unused in Linux 2.6)

	      Provides	much  of  the  information  in	/proc/[pid]/stat   and
	      /proc/[pid]/statm in a format that's easier for humans to parse.
	      Here's an example:

		  $ cat /proc/$$/status
		  Name:	  bash
		  State:  S (sleeping)
		  Tgid:	  3515
		  Pid:	  3515
		  PPid:	  3452
		  TracerPid:	  0
		  Uid:	  1000	  1000	  1000	  1000
		  Gid:	  100	  100	  100	  100
		  FDSize: 256
		  Groups: 16 33 100
		  VmPeak:     9136 kB
		  VmSize:     7896 kB
		  VmLck:	 0 kB
		  VmHWM:      7572 kB
		  VmRSS:      6316 kB
		  VmData:     5224 kB
		  VmStk:	88 kB
		  VmExe:       572 kB
		  VmLib:      1708 kB
		  VmPTE:	20 kB
		  Threads:	  1
		  SigQ:	  0/3067
		  SigPnd: 0000000000000000
		  ShdPnd: 0000000000000000
		  SigBlk: 0000000000010000
		  SigIgn: 0000000000384004
		  SigCgt: 000000004b813efb
		  CapInh: 0000000000000000
		  CapPrm: 0000000000000000
		  CapEff: 0000000000000000
		  CapBnd: ffffffffffffffff
		  Cpus_allowed:	  00000001
		  Cpus_allowed_list:	  0
		  Mems_allowed:	  1
		  Mems_allowed_list:	  0
		  voluntary_ctxt_switches:	  150
		  nonvoluntary_ctxt_switches:	  545

	      The fields are as follows:

	      * Name: Command run by this process.

	      * State: Current state of the process.  One of "R (running)", "S
		(sleeping)",  "D  (disk	 sleep)",  "T  (stopped)", "T (tracing
		stop)", "Z (zombie)", or "X (dead)".

	      * Tgid: Thread group ID (i.e., Process ID).

	      * Pid: Thread ID (see gettid(2)).

	      * TracerPid: PID of process tracing this process (0 if not being

	      * Uid,  Gid:  Real,  effective,  saved set, and file system UIDs

	      * FDSize: Number of file descriptor slots currently allocated.

	      * Groups: Supplementary group list.

	      * VmPeak: Peak virtual memory size.

	      * VmSize: Virtual memory size.

	      * VmLck: Locked memory size.

	      * VmHWM: Peak resident set size ("high water mark").

	      * VmRSS: Resident set size.

	      * VmData, VmStk, VmExe: Size of data, stack, and text segments.

	      * VmLib: Shared library code size.

	      * VmPTE: Page table entries size (since Linux 2.6.10).

	      * Threads: Number of threads in process containing this thread.

	      * SigPnd, ShdPnd: Number of signals pending for thread  and  for
		process as a whole (see pthreads(7) and signal(7)).

	      * SigBlk,	  SigIgn,   SigCgt:  Masks  indicating	signals	 being
		blocked, ignored, and caught (see signal(7)).

	      * CapInh, CapPrm,	 CapEff:  Masks	 of  capabilities  enabled  in
		inheritable,  permitted,  and  effective  sets	(see capabili‐

	      * CapBnd: Capability Bounding  set  (since  kernel  2.6.26,  see

	      * Cpus_allowed:  Mask  of	 CPUs  on  which  this process may run
		(since Linux 2.6.24, see cpuset(7)).

	      * Cpus_allowed_list: Same as  previous,  but  in	"list  format"
		(since Linux 2.6.26, see cpuset(7)).

	      * Mems_allowed:  Mask  of	 memory	 nodes allowed to this process
		(since Linux 2.6.24, see cpuset(7)).

	      * Mems_allowed_list: Same as  previous,  but  in	"list  format"
		(since Linux 2.6.26, see cpuset(7)).

	      * voluntary_context_switches,	nonvoluntary_context_switches:
		Number of voluntary and involuntary  context  switches	(since
		Linux 2.6.23).

       /proc/[pid]/task (since Linux 2.6.0-test6)
	      This  is	a  directory  that  contains one subdirectory for each
	      thread in the process.  The name of  each	 subdirectory  is  the
	      numerical	 thread	 ID  ([tid])  of  the  thread (see gettid(2)).
	      Within each of these subdirectories, there is  a	set  of	 files
	      with the same names and contents as under the /proc/[pid] direc‐
	      tories.  For attributes that are shared by all threads, the con‐
	      tents  for each of the files under the task/[tid] subdirectories
	      will be the same as in the  corresponding	 file  in  the	parent
	      /proc/[pid]  directory (e.g., in a multithreaded process, all of
	      the task/[tid]/cwd  files	 will  have  the  same	value  as  the
	      /proc/[pid]/cwd  file  in the parent directory, since all of the
	      threads in a process share a working directory).	For attributes
	      that are distinct for each thread, the corresponding files under
	      task/[tid] may have different values (e.g.,  various  fields  in
	      each  of	the  task/[tid]/status files may be different for each

	      In a multithreaded process, the contents of the /proc/[pid]/task
	      directory	 are not available if the main thread has already ter‐
	      minated (typically by calling pthread_exit(3)).

	      Advanced power management version and battery  information  when
	      CONFIG_APM is defined at kernel compilation time.

	      Contains subdirectories for installed busses.

	      Subdirectory  for	 PCMCIA	 devices  when CONFIG_PCMCIA is set at
	      kernel compilation time.


	      Contains various bus subdirectories and pseudo-files  containing
	      information  about  PCI  busses,	installed  devices, and device
	      drivers.	Some of these files are not ASCII.

	      Information about PCI devices.  They  may	 be  accessed  through
	      lspci(8) and setpci(8).

	      Arguments	 passed	 to the Linux kernel at boot time.  Often done
	      via a boot manager such as lilo(8) or grub(8).

       /proc/config.gz (since Linux 2.6)
	      This file exposes the configuration options that	were  used  to
	      build  the  currently running kernel, in the same format as they
	      would be shown in the .config file that resulted when  configur‐
	      ing  the	kernel	(using make xconfig, make config, or similar).
	      The file contents are compressed;	 view  or  search  them	 using
	      zcat(1), zgrep(1), etc.  As long as no changes have been made to
	      the following file, the contents of /proc/config.gz are the same
	      as those provided by :

		  cat /lib/modules/$(uname -r)/build/.config

	      /proc/config.gz  is  only	 provided  if the kernel is configured

	      This is a collection of CPU and  system  architecture  dependent
	      items,  for  each	 supported architecture a different list.  Two
	      common  entries  are  processor  which  gives  CPU  number   and
	      bogomips;	 a  system  constant  that is calculated during kernel
	      initialization.  SMP machines have information for each CPU.

	      Text listing of major numbers and device groups.	 This  can  be
	      used by MAKEDEV scripts for consistency with the kernel.

       /proc/diskstats (since Linux 2.5.69)
	      This  file  contains  disk  I/O statistics for each disk device.
	      See the kernel source file Documentation/iostats.txt for further

	      This  is a list of the registered ISA DMA (direct memory access)
	      channels in use.

	      Empty subdirectory.

	      List of the execution domains (ABI personalities).

	      Frame buffer information when CONFIG_FB is defined during kernel

	      A	 text  listing	of the file systems which are supported by the
	      kernel, namely file systems which were compiled into the	kernel
	      or  whose	 kernel	 modules  are  currently  loaded.   (See  also
	      filesystems(5).)	If a file system is marked with "nodev",  this
	      means  that  it  does  not  require a block device to be mounted
	      (e.g., virtual file system, network file system).

	      Incidentally, this file may be used by  mount(8)	when  no  file
	      system  is  specified and it didn't manage to determine the file
	      system type.  Then file systems contained in this file are tried
	      (excepted those that are marked with "nodev").

	      Empty subdirectory.

	      This  directory  exists  on systems with the IDE bus.  There are
	      directories for each IDE channel	and  attached  device.	 Files

		  cache		     buffer size in KB
		  capacity	     number of sectors
		  driver	     driver version
		  geometry	     physical and logical geometry
		  identify	     in hexadecimal
		  media		     media type
		  model		     manufacturer's model number
		  settings	     drive settings
		  smart_thresholds   in hexadecimal
		  smart_values	     in hexadecimal

	      The  hdparm(8)  utility provides access to this information in a
	      friendly format.

	      This is used to record the number of interrupts per CPU  per  IO
	      device.	Since  Linux 2.6.24, for the i386 and x86_64 architec‐
	      tures, at least, this also includes interrupts internal  to  the
	      system  (that is, not associated with a device as such), such as
	      NMI (nonmaskable interrupt), LOC (local  timer  interrupt),  and
	      for  SMP	systems,  TLB (TLB flush interrupt), RES (rescheduling
	      interrupt), CAL (remote function call interrupt),	 and  possibly
	      others.  Very easy to read formatting, done in ASCII.

	      I/O memory map in Linux 2.4.

	      This is a list of currently registered Input-Output port regions
	      that are in use.

       /proc/kallsyms (since Linux 2.5.71)
	      This holds the kernel exported symbol definitions	 used  by  the
	      modules(X)  tools to dynamically link and bind loadable modules.
	      In Linux 2.5.47 and earlier, a similar file with	slightly  dif‐
	      ferent syntax was named ksyms.

	      This  file  represents  the physical memory of the system and is
	      stored in the ELF core file format.  With this pseudo-file,  and
	      an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
	      used to examine the current state of any kernel data structures.

	      The total length of the file is  the  size  of  physical	memory
	      (RAM) plus 4KB.

	      This  file  can  be used instead of the syslog(2) system call to
	      read kernel messages.  A process must have superuser  privileges
	      to  read	this file, and only one process should read this file.
	      This file should not be read if  a  syslog  process  is  running
	      which uses the syslog(2) system call facility to log kernel mes‐

	      Information in this file is retrieved with the dmesg(8) program.

       /proc/ksyms (Linux 1.1.23-2.5.47)
	      See /proc/kallsyms.

	      The first three fields in this file  are	load  average  figures
	      giving  the number of jobs in the run queue (state R) or waiting
	      for disk I/O (state D) averaged over 1, 5, and 15 minutes.  They
	      are  the same as the load average numbers given by uptime(1) and
	      other programs.  The fourth field consists of two numbers	 sepa‐
	      rated  by a slash (/).  The first of these is the number of cur‐
	      rently  executing	  kernel   scheduling	entities   (processes,
	      threads); this will be less than or equal to the number of CPUs.
	      The value after the slash is the	number	of  kernel  scheduling
	      entities that currently exist on the system.  The fifth field is
	      the PID of the process that was most  recently  created  on  the

	      This  file  shows current file locks (flock(2) and fcntl(2)) and
	      leases (fcntl(2)).

       /proc/malloc (only up to and including Linux 2.2)
	      This file is only present	 if  CONFIG_DEBUG_MALLOC  was  defined
	      during compilation.

	      This  file  reports statistics about memory usage on the system.
	      It is used by free(1) to report the amount of free and used mem‐
	      ory (both physical and swap) on the system as well as the shared
	      memory and buffers used by the kernel.

	      A text list of the modules that have been loaded by the  system.
	      See also lsmod(8).

	      Before  kernel 2.4.19, this file was a list of all the file sys‐
	      tems currently mounted on the system.  With the introduction  of
	      per-process mount namespaces in Linux 2.4.19, this file became a
	      link to /proc/self/mounts, which lists the mount points  of  the
	      process's own mount namespace.  The format of this file is docu‐
	      mented in fstab(5).

	      Memory Type Range Registers.  See the kernel source  file	 Docu‐
	      mentation/mtrr.txt for details.

	      various  net  pseudo-files, all of which give the status of some
	      part of the networking layer.  These files contain ASCII	struc‐
	      tures  and  are,	therefore, readable with cat(1).  However, the
	      standard netstat(8) suite provides much cleaner access to	 these

	      This  holds  an ASCII readable dump of the kernel ARP table used
	      for address resolutions.	It will show both dynamically  learned
	      and pre-programmed ARP entries.  The format is:

	IP address     HW type	 Flags	   HW address	       Mask   Device   0x1	 0x2	   00:50:BF:25:68:F3   *      eth0  0x1	 0xc	   00:00:00:00:00:00   *      eth0

	      Here "IP address" is the IPv4 address of the machine and the "HW
	      type" is the hardware type of the	 address  from	RFC 826.   The
	      flags are the internal flags of the ARP structure (as defined in
	      /usr/include/linux/if_arp.h) and the "HW address"	 is  the  data
	      link layer mapping for that IP address if it is known.

	      The  dev pseudo-file contains network device status information.
	      This gives the number of received and sent packets,  the	number
	      of  errors and collisions and other basic statistics.  These are
	      used by the ifconfig(8) program to report	 device	 status.   The
	      format is:

 Inter-|   Receive						  |  Transmit
  face |bytes	 packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0	 0    0	    0	       0	 0  2776770   11307    0    0	 0     0       0	  0
   eth0: 1215645    2751    0	 0    0	    0	       0	 0  1782404    4324    0    0	 0   427       0	  0
   ppp0: 1622270    5552    1	 0    0	    0	       0	 0   354130    5669    0    0	 0     0       0	  0
   tap0:    7714      81    0	 0    0	    0	       0	 0     7714	 81    0    0	 0     0       0	  0

	      Defined in /usr/src/linux/net/core/dev_mcast.c:
		   indx interface_name	dmi_u dmi_g dmi_address
		   2	eth0		1     0	    01005e000001
		   3	eth1		1     0	    01005e000001
		   4	eth2		1     0	    01005e000001

	      Internet	   Group     Management	   Protocol.	 Defined    in

	      This file uses the same format as the arp file and contains  the
	      current reverse mapping database used to provide rarp(8) reverse
	      address lookup services.	If RARP is  not	 configured  into  the
	      kernel, this file will not be present.

	      Holds  a	dump of the RAW socket table.  Much of the information
	      is not of use apart from debugging.  The "sl" value is the  ker‐
	      nel  hash	 slot for the socket, the "local_address" is the local
	      address and protocol number pair.	 "St" is the  internal	status
	      of  the  socket.	The "tx_queue" and "rx_queue" are the outgoing
	      and incoming data queue in terms of kernel  memory  usage.   The
	      "tr", "tm->when", and "rexmits" fields are not used by RAW.  The
	      "uid" field holds the  effective	UID  of	 the  creator  of  the

	      This file holds the ASCII data needed for the IP, ICMP, TCP, and
	      UDP management information bases for an SNMP agent.

	      Holds a dump of the TCP socket table.  Much of  the  information
	      is  not of use apart from debugging.  The "sl" value is the ker‐
	      nel hash slot for the socket, the "local_address" is  the	 local
	      address  and  port number pair.  The "rem_address" is the remote
	      address and port number pair (if connected).  "St" is the inter‐
	      nal status of the socket.	 The "tx_queue" and "rx_queue" are the
	      outgoing and incoming data  queue	 in  terms  of	kernel	memory
	      usage.  The "tr", "tm->when", and "rexmits" fields hold internal
	      information of the kernel socket state and are only  useful  for
	      debugging.   The "uid" field holds the effective UID of the cre‐
	      ator of the socket.

	      Holds a dump of the UDP socket table.  Much of  the  information
	      is  not of use apart from debugging.  The "sl" value is the ker‐
	      nel hash slot for the socket, the "local_address" is  the	 local
	      address  and  port number pair.  The "rem_address" is the remote
	      address and port number pair (if connected). "St" is the	inter‐
	      nal status of the socket.	 The "tx_queue" and "rx_queue" are the
	      outgoing and incoming data  queue	 in  terms  of	kernel	memory
	      usage.   The "tr", "tm->when", and "rexmits" fields are not used
	      by UDP.  The "uid" field holds the effective UID of the  creator
	      of the socket.  The format is:

 sl  local_address rem_address	 st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

	      Lists  the  Unix	domain	sockets	 present within the system and
	      their status.  The format is:
	      Num RefCount Protocol Flags    Type St Path
	       0: 00000002 00000000 00000000 0001 03
	       1: 00000001 00000000 00010000 0001 01 /dev/printer

	      Here "Num" is the kernel table slot number,  "RefCount"  is  the
	      number of users of the socket, "Protocol" is currently always 0,
	      "Flags" represent the internal kernel flags holding  the	status
	      of the socket.  Currently, type is always "1" (Unix domain data‐
	      gram sockets are not yet supported in the kernel).  "St" is  the
	      internal state of the socket and Path is the bound path (if any)
	      of the socket.

	      Contains major and minor numbers of each partition  as  well  as
	      number of blocks and partition name.

	      This  is	a  listing of all PCI devices found during kernel ini‐
	      tialization and their configuration.

	      This file has been deprecated in favor of a new /proc  interface
	      for  PCI	(/proc/bus/pci).   It  became  optional	 in  Linux 2.2
	      (available with CONFIG_PCI_OLD_PROC set at kernel	 compilation).
	      It  became once more non-optionally enabled in Linux 2.4.	 Next,
	      it was deprecated	 in  Linux  2.6	 (still	 available  with  CON‐
	      FIG_PCI_LEGACY_PROC  set),  and finally removed altogether since
	      Linux 2.6.17.

	      A directory with the scsi mid-level pseudo-file and various SCSI
	      low-level driver directories, which contain a file for each SCSI
	      host in this system, all of which give the status of  some  part
	      of  the SCSI IO subsystem.  These files contain ASCII structures
	      and are, therefore, readable with cat(1).

	      You can also write to some of the files to reconfigure the  sub‐
	      system or switch certain features on or off.

	      This  is a listing of all SCSI devices known to the kernel.  The
	      listing is similar to the one seen  during  bootup.   scsi  cur‐
	      rently  supports only the add-single-device command which allows
	      root to add a hotplugged device to the list of known devices.

	      The command

		  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi

	      will cause host scsi1 to scan on SCSI channel 0 for a device  on
	      ID  5 LUN 0.  If there is already a device known on this address
	      or the address is invalid, an error will be returned.

	      [drivername]  can	 currently  be	NCR53c7xx,  aha152x,  aha1542,
	      aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,
	      pas16, qlogic, scsi_debug, seagate, t128,	 u15-24f,  ultrastore,
	      or  wd7000.  These directories show up for all drivers that reg‐
	      istered at least one SCSI HBA.   Every  directory	 contains  one
	      file  per	 registered  host.  Every host-file is named after the
	      number the host was assigned during initialization.

	      Reading these files will usually show driver and host configura‐
	      tion, statistics, etc.

	      Writing  to  these  files	 allows	 different things on different
	      hosts.  For example, with the latency  and  nolatency  commands,
	      root  can	 switch on and off command latency measurement code in
	      the eata_dma driver.  With the lockup and unlock commands,  root
	      can control bus lockups simulated by the scsi_debug driver.

	      This  directory  refers  to the process accessing the /proc file
	      system, and is identical to the /proc  directory	named  by  the
	      process ID of the same process.

	      Information  about  kernel caches.  Since Linux 2.6.16 this file
	      is only present if the CONFIG_SLAB kernel	 configuration	option
	      is enabled.  The columns in /proc/slabinfo are:


	      See slabinfo(5) for details.

	      kernel/system  statistics.   Varies  with	 architecture.	Common
	      entries include:

	      cpu  3357 0 4313 1362393
		     The  amount  of  time,  measured  in  units  of   USER_HZ
		     (1/100ths	 of   a	 second	 on  most  architectures,  use
		     sysconf(_SC_CLK_TCK) to obtain the right value), that the
		     system  spent  in	user mode, user mode with low priority
		     (nice), system mode, and  the  idle  task,	 respectively.
		     The  last	value should be USER_HZ times the second entry
		     in the uptime pseudo-file.

		     In Linux 2.6 this line includes three additional columns:
		     iowait - time waiting for I/O to complete (since 2.5.41);
		     irq -  time  servicing  interrupts	 (since	 2.6.0-test4);
		     softirq - time servicing softirqs (since 2.6.0-test4).

		     Since  Linux  2.6.11,  there is an eighth column, steal -
		     stolen time, which is the time spent in  other  operating
		     systems when running in a virtualized environment

		     Since Linux 2.6.24, there is a ninth column, guest, which
		     is the time spent running a virtual CPU for guest operat‐
		     ing systems under the control of the Linux kernel.

	      page 5741 1808
		     The  number  of  pages the system paged in and the number
		     that were paged out (from disk).

	      swap 1 0
		     The number of swap pages that have been  brought  in  and

	      intr 1462898
		     This  line shows counts of interrupts serviced since boot
		     time, for each of the possible  system  interrupts.   The
		     first  column  is	the  total of all interrupts serviced;
		     each subsequent column is	the  total  for	 a  particular

	      disk_io: (2,0):(31,30,5764,1,2) (3,0):...
		     (major,disk_idx):(noinfo,	   read_io_ops,	    blks_read,
		     write_io_ops, blks_written)
		     (Linux 2.4 only)

	      ctxt 115315
		     The number of context switches that the system underwent.

	      btime 769041601
		     boot time, in seconds since the Epoch (January 1, 1970).

	      processes 86031
		     Number of forks since boot.

	      procs_running 6
		     Number of processes in  runnable  state.	(Linux	2.5.45

	      procs_blocked 2
		     Number  of processes blocked waiting for I/O to complete.
		     (Linux 2.5.45 onwards.)

	      Swap areas in use.  See also swapon(8).

	      This directory (present since 1.3.57) contains a number of files
	      and  subdirectories  corresponding  to  kernel variables.	 These
	      variables can be read and sometimes  modified  using  the	 /proc
	      file   system,  and  the	(deprecated)  sysctl(2)	 system	 call.
	      Presently, there are subdirectories abi, debug, dev, fs, kernel,
	      net, proc, rxrpc, sunrpc and vm that each contain more files and

       /proc/sys/abi (since Linux 2.4.10)
	      This directory may contain files with application binary	infor‐
	      mation.  See the kernel source file Documentation/sysctl/abi.txt
	      for more information.

	      This directory may be empty.

	      This  directory  contains	 device-specific  information	(e.g.,
	      dev/cdrom/info).	On some systems, it may be empty.

	      This  contains  the  subdirectories binfmt_misc, epoll, inotify,
	      and mqueue, and files dentry-state, dir-notify-enable, dquot-nr,
	      file-max,	 file-nr,  inode-max,  inode-nr,  inode-state,	lease-
	      break-time,     leases-enable,	 overflowgid,	  overflowuid,
	      suid_dumpable, super-max, and super-nr.

	      Documentation  for  files	 in this directory can be found in the
	      kernel sources in Documentation/binfmt_misc.txt.

       /proc/sys/fs/dentry-state (since Linux 2.2)
	      This file contains information about the status of the directory
	      cache  (dcache).	 The  file  contains  six  numbers, nr_dentry,
	      nr_unused,  age_limit  (age  in  seconds),   want_pages	(pages
	      requested by system) and two dummy values.

	      * nr_dentry   is	 the  number  of  allocated  dentries  (dcache
		entries).  This field is unused in Linux 2.2.

	      * nr_unused is the number of unused dentries.

	      * age_limit is the age in seconds after which dcache entries can
		be reclaimed when memory is short.

	      * want_pages   is	  non-zero   when   the	  kernel   has	called
		shrink_dcache_pages() and the dcache isn't pruned yet.

	      This file can be used to disable or enable the dnotify interface
	      described	 in  fcntl(2) on a system-wide basis.  A value of 0 in
	      this file disables the interface, and a value of 1 enables it.

	      This file shows the maximum number of cached disk quota entries.
	      On some (2.4) systems, it is not present.	 If the number of free
	      cached disk quota entries is very low and you have some  awesome
	      number of simultaneous system users, you might want to raise the

	      This file shows the number of allocated disk quota  entries  and
	      the number of free disk quota entries.

       /proc/sys/fs/epoll (since Linux 2.6.28)
	      This  directory contains the file max_user_watches, which can be
	      used to limit the amount of kernel memory consumed by the	 epoll
	      interface.  For further details, see inotify(7).

	      This  file  defines  a  system-wide  limit on the number of open
	      files for all processes.	(See also setrlimit(2), which  can  be
	      used  by	a process to set the per-process limit, RLIMIT_NOFILE,
	      on the number of files it may open.)  If you get lots  of	 error
	      messages	about running out of file handles, try increasing this

	      echo 100000 > /proc/sys/fs/file-max

	      The kernel constant NR_OPEN imposes an upper limit on the	 value
	      that may be placed in file-max.

	      If  you  increase	 /proc/sys/fs/file-max,	 be  sure  to increase
	      /proc/sys/fs/inode-max  to  3-4	times	the   new   value   of
	      /proc/sys/fs/file-max, or you will run out of inodes.

	      Historically,  the  kernel  was  able  to	 allocate file handles
	      dynamically, but not to free them again.	The  three  values  in
	      file-nr  denote the number of allocated file handles, the number
	      of allocated but unused file handles, and the maximum number  of
	      file  handles.  Linux 2.6 always reports 0 as the number of free
	      file handles -- this is not an error, it	just  means  that  the
	      number  of  allocated file handles exactly matches the number of
	      used file handles.

	      This file contains the maximum number of in-memory  inodes.   On
	      some (2.4) systems, it may not be present.  This value should be
	      3-4 times larger than the value in file-max, since stdin, stdout
	      and network sockets also need an inode to handle them.  When you
	      regularly run out of inodes, you need to increase this value.

	      This file contains the first two values from inode-state.

	      This file contains  seven	 numbers:  nr_inodes,  nr_free_inodes,
	      preshrink,  and  four  dummy values.  nr_inodes is the number of
	      inodes the system has allocated.	This can be slightly more than
	      inode-max	 because Linux allocates them one page full at a time.
	      nr_free_inodes represents the number of free inodes.   preshrink
	      is  non-zero when the nr_inodes > inode-max and the system needs
	      to prune the inode list instead of allocating more.

       /proc/sys/fs/inotify (since Linux 2.6.13)
	      This     directory     contains	  files	    max_queued_events,
	      max_user_instances,  and	max_user_watches,  that can be used to
	      limit the amount of kernel memory consumed by the inotify inter‐
	      face.  For further details, see inotify(7).

	      This file specifies the grace period that the kernel grants to a
	      process holding a file lease (fcntl(2)) after it has sent a sig‐
	      nal to that process notifying it that another process is waiting
	      to open the file.	 If the lease holder does not remove or	 down‐
	      grade  the  lease	 within this grace period, the kernel forcibly
	      breaks the lease.

	      This  file  can  be  used	 to  enable  or	 disable  file	leases
	      (fcntl(2))  on  a	 system-wide basis.  If this file contains the
	      value 0, leases are disabled.  A non-zero value enables leases.

       /proc/sys/fs/mqueue (since Linux 2.6.6)
	      This  directory  contains	 files	 msg_max,   msgsize_max,   and
	      queues_max,  controlling	the  resources	used  by POSIX message
	      queues.  See mq_overview(7) for details.

       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
	      These files allow you to change the value of the fixed  UID  and
	      GID.   The  default  is  65534.	Some file systems only support
	      16-bit UIDs and GIDs, although in Linux UIDs  and	 GIDs  are  32
	      bits.   When  one	 of  these file systems is mounted with writes
	      enabled, any UID or GID that would exceed 65535 is translated to
	      the overflow value before being written to disk.

       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
	      The  value  in  this file determines whether core dump files are
	      produced for set-user-ID or  otherwise  protected/tainted	 bina‐
	      ries.  Three different integer values can be specified:

	      0 (default)  This	 provides  the	traditional (pre-Linux 2.6.13)
	      behavior.	 A core dump will not be produced for a process	 which
	      has  changed  credentials	 (by calling seteuid(2), setgid(2), or
	      similar, or by executing a set-user-ID or set-group-ID  program)
	      or whose binary does not have read permission enabled.

	      1 ("debug")  All	processes  dump	 core when possible.  The core
	      dump is owned by the file system user ID of the dumping  process
	      and  no security is applied.  This is intended for system debug‐
	      ging situations only.  Ptrace is unchecked.

	      2 ("suidsafe") Any binary which normally	would  not  be	dumped
	      (see  "0"	 above)	 is dumped readable by root only.  This allows
	      the user to remove the core dump file but not to read  it.   For
	      security	reasons core dumps in this mode will not overwrite one
	      another or other files.  This mode is appropriate when  adminis‐
	      trators  are  attempting	to debug problems in a normal environ‐

	      This file controls the maximum number of superblocks,  and  thus
	      the  maximum number of mounted file systems the kernel can have.
	      You only need to increase super-max if you need  to  mount  more
	      file systems than the current value in super-max allows you to.

	      This file contains the number of file systems currently mounted.

	      This  directory  contains	 files	controlling  a range of kernel
	      parameters, as described below.

	      This file contains three numbers: highwater, lowwater, and  fre‐
	      quency.  If BSD-style process accounting is enabled these values
	      control its behavior.  If free space on file  system  where  the
	      log  lives  goes below lowwater percent accounting suspends.  If
	      free space gets  above  highwater	 percent  accounting  resumes.
	      frequency	 determines  how often the kernel checks the amount of
	      free space (value is in seconds).	 Default values are 4,	2  and
	      30.   That  is,  suspend accounting if 2% or less space is free;
	      resume it if 4% or more  space  is  free;	 consider  information
	      about amount of free space valid for 30 seconds.

       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
	      This  file holds the value of the kernel capability bounding set
	      (expressed as a signed  decimal  number).	  This	set  is	 ANDed
	      against	the   capabilities   permitted	to  a  process	during
	      execve(2).  Starting with Linux 2.6.25, the system-wide capabil‐
	      ity  bounding  set disappeared, and was replaced by a per-thread
	      bounding set; see capabilities(7).

	      See core(5).

	      See core(5).

	      This file controls the handling of Ctrl-Alt-Del  from  the  key‐
	      board.   When  the  value	 in  this  file	 is 0, Ctrl-Alt-Del is
	      trapped and sent to the init(8) program  to  handle  a  graceful
	      restart.	 When the value is greater than zero, Linux's reaction
	      to a Vulcan Nerve Pinch (tm) will be an immediate reboot,	 with‐
	      out  even syncing its dirty buffers.  Note: when a program (like
	      dosemu) has the keyboard in  "raw"  mode,	 the  ctrl-alt-del  is
	      intercepted by the program before it ever reaches the kernel tty
	      layer, and it's up to the program to decide what to do with it.

	      The value in this file determines who can see kernel syslog con‐
	      tents.   A  value of 0 in this file imposes no restrictions.  If
	      the value is 1, only privileged users can read the  kernel  sys‐
	      log.   (See  syslog(2) for more details.)	 Since Linux 3.4, only
	      users with the CAP_SYS_ADMIN capability may change the value  in
	      this file.

	      This  file  contains the path for the hotplug policy agent.  The
	      default value in this file is /sbin/hotplug.

       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
	      can be used to set the NIS/YP domainname	and  the  hostname  of
	      your  box	 in exactly the same way as the commands domainname(1)
	      and hostname(1), that is:

		  # echo 'darkstar' > /proc/sys/kernel/hostname
		  # echo 'mydomain' > /proc/sys/kernel/domainname

	      has the same effect as

		  # hostname 'darkstar'
		  # domainname 'mydomain'

	      Note, however, that the classic has the	 host‐
	      name "darkstar" and DNS (Internet Domain Name Server) domainname
	      "", not to be confused with the NIS (Network Information
	      Service)	or  YP	(Yellow	 Pages)	 domainname.  These two domain
	      names are in general different.  For a detailed  discussion  see
	      the hostname(1) man page.

	      (PowerPC only) If this file is set to a non-zero value, the Pow‐
	      erPC htab (see kernel  file  Documentation/powerpc/ppc_htab.txt)
	      is pruned each time the system hits the idle loop.

	      The  value  in this file determines whether kernel addresses are
	      exposed via /proc files and other interfaces.  A value of	 0  in
	      this  file  imposes  no restrictions.  If the value is 1, kernel
	      pointers printed using the %pK format specifier will be replaced
	      with  zeros  unless  the user has the CAP_SYSLOG capability.  If
	      the value is 2, kernel pointers printed  using  the  %pK	format
	      specifier	 will  be replaced with zeros regardless of the user's
	      capabilities.  The initial default value for this	 file  was  1,
	      but  the	default was changed to 0 in Linux 2.6.39.  Since Linux
	      3.4, only users with the CAP_SYS_ADMIN capability can change the
	      value in this file.

	      (PowerPC	only)  This  file contains a flag that controls the L2
	      cache of G3 processor boards.  If	 0,  the  cache	 is  disabled.
	      Enabled if non-zero.

	      This  file  contains the path for the kernel module loader.  The
	      default value is /sbin/modprobe.	The file is  only  present  if
	      the  kernel is built with the CONFIG_KMOD option enabled.	 It is
	      described by the kernel source file Documentation/kmod.txt (only
	      present in kernel 2.4 and earlier).

	      This  file  defines  a  system-wide limit specifying the maximum
	      number of bytes in a single message written on a System  V  mes‐
	      sage queue.

	      This file defines the system-wide limit on the number of message
	      queue identifiers.  (This file is	 only  present	in  Linux  2.4

	      This file defines a system-wide parameter used to initialize the
	      msg_qbytes setting for subsequently created message queues.  The
	      msg_qbytes  setting  specifies  the maximum number of bytes that
	      may be written to the message queue.

       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
	      These files give substrings of /proc/version.

       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
	      These files duplicate  the  files	 /proc/sys/fs/overflowgid  and

	      This  file  gives	 read/write  access  to	 the  kernel  variable
	      panic_timeout.  If this is zero,	the  kernel  will  loop	 on  a
	      panic;  if  non-zero it indicates that the kernel should autore‐
	      boot after this number of seconds.  When you  use	 the  software
	      watchdog device driver, the recommended setting is 60.

       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
	      This  file controls the kernel's behavior when an oops or BUG is
	      encountered.  If this file contains 0, then the system tries  to
	      continue	operation.  If it contains 1, then the system delays a
	      few seconds (to give klogd time to record the oops  output)  and
	      then  panics.   If  the /proc/sys/kernel/panic file is also non-
	      zero then the machine will be rebooted.

       /proc/sys/kernel/pid_max( since Linux 2.5.34)
	      This file specifies the value at which PIDs wrap	around	(i.e.,
	      the  value  in  this  file is one greater than the maximum PID).
	      The default value for this file,	32768,	results	 in  the  same
	      range of PIDs as on earlier kernels.  On 32-bit platforms, 32768
	      is the maximum value for pid_max.	 On  64-bit  systems,  pid_max
	      can be set to any value up to 2^22 (PID_MAX_LIMIT, approximately
	      4 million).

       /proc/sys/kernel/powersave-nap (PowerPC only)
	      This file contains a flag.  If set, Linux-PPC will use the "nap"
	      mode of powersaving, otherwise the "doze" mode will be used.

	      The  four values in this file are console_loglevel, default_mes‐
	      sage_loglevel,	minimum_console_level,	  and	  default_con‐
	      sole_loglevel.   These  values  influence printk() behavior when
	      printing or logging error messages.  See syslog(2) for more info
	      on  the  different  loglevels.   Messages with a higher priority
	      than console_loglevel will be printed to the console.   Messages
	      without  an  explicit  priority  will  be	 printed with priority
	      default_message_level.  minimum_console_loglevel is the  minimum
	      (highest)	  value	  to   which   console_loglevel	 can  be  set.
	      default_console_loglevel	is  the	  default   value   for	  con‐

       /proc/sys/kernel/pty (since Linux 2.6.4)
	      This directory contains two files relating to the number of Unix
	      98 pseudo-terminals (see pts(4)) on the system.

	      This file defines the maximum number of pseudo-terminals.

	      This read-only file indicates how many pseudo-terminals are cur‐
	      rently in use.

	      This directory contains various parameters controlling the oper‐
	      ation of the file /dev/random.  See random(4) for further infor‐

	      This  file  is  documented  in the kernel source file Documenta‐

       /proc/sys/kernel/reboot-cmd (Sparc only)
	      This file seems to be a way to give an  argument	to  the	 SPARC
	      ROM/Flash	 boot  loader.	 Maybe	to  tell  it  what to do after

	      (Only in kernels up to and including  2.6.7;  see	 setrlimit(2))
	      This  file can be used to tune the maximum number of POSIX real-
	      time (queued) signals that can be outstanding in the system.

	      (Only in kernels up to and including 2.6.7.)   This  file	 shows
	      the number POSIX real-time signals currently queued.

       /proc/sys/kernel/sem (since Linux 2.4)
	      This  file  contains  4 numbers defining limits for System V IPC
	      semaphores.  These fields are, in order:

	      SEMMSL  The maximum semaphores per semaphore set.

	      SEMMNS  A system-wide limit on the number of semaphores  in  all
		      semaphore sets.

	      SEMOPM  The  maximum  number of operations that may be specified
		      in a semop(2) call.

	      SEMMNI  A system-wide limit on the maximum number	 of  semaphore

	      This file shows the size of the generic SCSI device (sg) buffer.
	      You can't tune it just yet, but you could change it  at  compile
	      time  by	editing	 include/scsi/sg.h  and	 changing the value of
	      SG_BIG_BUFF.  However, there shouldn't be any reason  to	change
	      this value.

	      This  file contains the system-wide limit on the total number of
	      pages of System V shared memory.

	      This file can be used to query and set the run-time limit on the
	      maximum  (System	V  IPC) shared memory segment size that can be
	      created.	Shared memory segments up to 1GB are now supported  in
	      the kernel.  This value defaults to SHMMAX.

	      (available  in  Linux  2.4  and onwards) This file specifies the
	      system-wide maximum number of System V  shared  memory  segments
	      that can be created.

	      This  file  controls  the functions allowed to be invoked by the
	      SysRq key.  By default, the file contains 1 meaning  that	 every
	      possible	SysRq  request	is  allowed (in older kernel versions,
	      SysRq was disabled by default, and you were required to specifi‐
	      cally enable it at run-time, but this is not the case any more).
	      Possible values in this file are:

		 0 - disable sysrq completely
		 1 - enable all functions of sysrq
		>1 - bitmask of allowed sysrq functions, as follows:
			2 - enable control of console logging level
			4 - enable control of keyboard (SAK, unraw)
			8 - enable debugging dumps of processes etc.
		       16 - enable sync command
		       32 - enable remount read-only
		       64 - enable signalling of processes (term,  kill,  oom-
		      128 - allow reboot/poweroff
		      256 - allow nicing of all real-time tasks

	      This  file is only present if the CONFIG_MAGIG_SYSRQ kernel con‐
	      figuration option is enabled.  For further details see the  ker‐
	      nel source file Documentation/sysrq.txt.

	      This file contains a string like:

		  #5 Wed Feb 25 21:49:24 MET 1998

	      The  "#5"	 means	that  this is the fifth kernel built from this
	      source base and the date behind it indicates the time the kernel
	      was built.

       /proc/sys/kernel/threads-max (since Linux 2.3.11)
	      This  file  specifies  the  system-wide  limit  on the number of
	      threads (tasks) that can be created on the system.

       /proc/sys/kernel/zero-paged (PowerPC only)
	      This file contains a flag.  When enabled	(non-zero),  Linux-PPC
	      will  pre-zero  pages  in	 the  idle  loop, possibly speeding up

	      This directory contains networking stuff.	 Explanations for some
	      of  the  files  under  this directory can be found in tcp(7) and

	      This file defines a ceiling value for the	 backlog  argument  of
	      listen(2); see the listen(2) manual page for details.

	      This directory may be empty.

	      This  directory  supports	 Sun remote procedure call for network
	      file system (NFS).  On some systems, it is not present.

	      This directory contains files for memory management tuning, buf‐
	      fer and cache management.

       /proc/sys/vm/drop_caches (since Linux 2.6.16)
	      Writing  to  this	 file  causes the kernel to drop clean caches,
	      dentries and inodes from memory, causing that memory  to	become

	      To  free	pagecache,  use	 echo 1 > /proc/sys/vm/drop_caches; to
	      free dentries and inodes, use echo 2 > /proc/sys/vm/drop_caches;
	      to   free	  pagecache,   dentries	 and  inodes,  use  echo  3  >

	      Because this is a non-destructive operation  and	dirty  objects
	      are not freeable, the user should run sync(8) first.

	      The value in this file controls how aggressively the kernel will
	      swap memory pages.  Higher values increase agressiveness,	 lower
	      values descrease aggressiveness.	The default value is 60.

       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
	      If non-zero, this disables the new 32-bit memory-mapping layout;
	      the kernel will use the legacy (2.4) layout for all processes.

       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
	      Enables a system-wide task dump (excluding kernel threads) to be
	      produced	when  the  kernel  performs  an OOM-killing.  The dump
	      includes	the  following	information  for  each	task  (thread,
	      process): thread ID, real user ID, thread group ID (process ID),
	      virtual memory size, resident set size, the CPU that the task is
	      scheduled	  on,	oom_adj	  score	  (see	 the   description  of
	      /proc/[pid]/oom_adj), and command	 name.	 This  is  helpful  to
	      determine	 why  the  OOM-killer  was invoked and to identify the
	      rogue task that caused it.

	      If this contains the value zero, this information is suppressed.
	      On  very	large  systems	with thousands of tasks, it may not be
	      feasible to dump the memory  state  information  for  each  one.
	      Such systems should not be forced to incur a performance penalty
	      in OOM situations when the information may not be desired.

	      If this is set to non-zero, this information is  shown  whenever
	      the OOM-killer actually kills a memory-hogging task.

	      The default value is 0.

       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
	      This enables or disables killing the OOM-triggering task in out-
	      of-memory situations.

	      If this is set to zero, the OOM-killer  will  scan  through  the
	      entire  tasklist	and select a task based on heuristics to kill.
	      This normally selects a rogue memory-hogging task that frees  up
	      a large amount of memory when killed.

	      If this is set to non-zero, the OOM-killer simply kills the task
	      that triggered the out-of-memory condition.  This avoids a  pos‐
	      sibly expensive tasklist scan.

	      If  /proc/sys/vm/panic_on_oom  is	 non-zero, it takes precedence
	      over whatever value is  used  in	/proc/sys/vm/oom_kill_allocat‐

	      The default value is 0.

	      This  file  contains  the kernel virtual memory accounting mode.
	      Values are:

		     0: heuristic overcommit (this is the default)
		     1: always overcommit, never check
		     2: always check, never overcommit

	      In mode 0, calls of mmap(2) with MAP_NORESERVE are not  checked,
	      and  the default check is very weak, leading to the risk of get‐
	      ting a process "OOM-killed".  Under Linux 2.4 any non-zero value
	      implies  mode  1.	  In  mode  2 (available since Linux 2.6), the
	      total virtual address space on the system is limited  to	(SS  +
	      RAM*(r/100)), where SS is the size of the swap space, and RAM is
	      the size of the physical memory, and r is the  contents  of  the
	      file /proc/sys/vm/overcommit_ratio.

	      See the description of /proc/sys/vm/overcommit_memory.

       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
	      This enables or disables a kernel panic in an out-of-memory sit‐

	      If this file is set to the value 0, the kernel's OOM-killer will
	      kill  some  rogue	 process.   Usually, the OOM-killer is able to
	      kill a rogue process and the system will survive.

	      If this file is set to the value 1,  then	 the  kernel  normally
	      panics when out-of-memory happens.  However, if a process limits
	      allocations to certain nodes  using  memory  policies  (mbind(2)
	      MPOL_BIND)  or  cpusets (cpuset(7)) and those nodes reach memory
	      exhaustion status, one process may be killed by the  OOM-killer.
	      No panic occurs in this case: because other nodes' memory may be
	      free, this means the system as a whole may not have  reached  an
	      out-of-memory situation yet.

	      If  this	file  is  set to the value 2, the kernel always panics
	      when an out-of-memory condition occurs.

	      The default value is 0.  1 and 2 are for failover of clustering.
	      Select either according to your policy of failover.

       /proc/sysrq-trigger (since Linux 2.4.21)
	      Writing  a  character to this file triggers the same SysRq func‐
	      tion as typing ALT-SysRq-<character>  (see  the  description  of
	      /proc/sys/kernel/sysrq).	This file is normally only writable by
	      root.  For further details see the kernel source file Documenta‐

	      Subdirectory  containing	the  pseudo-files  msg,	 sem  and shm.
	      These files list the System V Interprocess  Communication	 (IPC)
	      objects  (respectively:  message	queues, semaphores, and shared
	      memory) that currently exist on the  system,  providing  similar
	      information  to  that  available	via ipcs(1).  These files have
	      headers and are formatted (one IPC object	 per  line)  for  easy
	      understanding.   svipc(7)	 provides  further  background	on the
	      information shown by these files.

	      Subdirectory containing the pseudo-files and subdirectories  for
	      tty drivers and line disciplines.

	      This  file  contains two numbers: the uptime of the system (sec‐
	      onds), and the amount of time spent in idle process (seconds).

	      This string identifies the kernel version that is currently run‐
	      ning.   It  includes  the	 contents  of /proc/sys/kernel/ostype,
	      /proc/sys/kernel/osrelease  and  /proc/sys/kernel/version.   For
	    Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994

       /proc/vmstat (since Linux 2.6)
	      This file displays various virtual memory statistics.

       /proc/zoneinfo (since Linux 2.6.13)
	      This  file display information about memory zones.  This is use‐
	      ful for analyzing virtual memory behavior.

       Many strings (i.e., the environment and command line) are in the inter‐
       nal format, with sub-fields terminated by null bytes ('\0'), so you may
       find that things are more readable if you use od -c or tr  "\000"  "\n"
       to read them.  Alternatively, echo `cat <file>` works well.

       This manual page is incomplete, possibly inaccurate, and is the kind of
       thing that needs to be updated very often.

       cat(1), find(1), free(1), ps(1), tr(1), uptime(1), chroot(2),  mmap(2),
       readlink(2),   syslog(2),   slabinfo(5),	  hier(7),   time(7),  arp(8),
       dmesg(8),  hdparm(8),   ifconfig(8),   init(8),	 lsmod(8),   lspci(8),
       mount(8), netstat(8), procinfo(8), route(8)
       The kernel source files: Documentation/filesystems/proc.txt, Documenta‐

       This page is part of release 3.22 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at

Linux				  2009-03-30			       PROC(5)

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