btextract(8)btextract(8)NAMEbtextract - Extracts the file systems from tape in single-user mode in
The btextract command is a shell script that restores file systems from
tapes that contain the bootable Standalone System (SAS) kernel. The
SAS kernel is created using the btcreate utility. You can perform a
default restore or an advanced restore operation.
Use the default restore option when you want to duplicate the custom‐
ized system on more than one machine of the same hardware platform
type. When you perform a default restore, you cannot specify which
disk partitions to use. Instead, the btextract command restores file
systems using the disk partition information gathered during the btcre‐
ate session. The restore operation overwrites all existing information
on the target drive.
To perform a default restore operation, the disk configuration of the
system you backed up must be the same as the system you are restoring.
Use the diskconfig GUI or the disklabel and newfs commands to prepare a
disk to receive the extracted tape contents.
During an advanced restore operation, the btextract command prompts you
to enter the name of a disk partition. The file systems are restored to
the specified partition.
During an advanced restore operation, the btextract command assigns the
b partition of the root disk as the swap partition.
You cannot restore a file system that is more than 100% full to a par‐
tition of the same size as the original partition. During the restore
of the UFS file system, the /sbin/restore command adds a new file named
restoresymtable. The presence of this restoresymtable file can make the
restored file system larger than the source partition size listed in
the output from the /sbin/disklabel command.
For example, on the source system, the disklabel shows the target h
partition to be:
h: 86758 1212416 4.2BSD
The UFS file system is as follows:
Filesystem 512-blocks Used Available Capacity Mounted on
/dev/dsk8h 83812 83786 0 112% /bootable
The file system is 112% full. This file system cannot be restored on
the target file system of 86758 blocks (512-byte blocks), because the
following file is created by the /sbin/restore command.
-rw-r--r-- 1 root system 27368 Jul 2 09:33 restoresymtable
The /sbin/restore command creates a restoresymtable file that exceeds
the 112% range. The solution is to use a partition of about 86996
(512-byte blocks), about 3.8% larger than the actual file size.
To use the btextract utility, place the system in a halt state, ini‐
tialize the system, then boot from the tape as follows: >>> init >>>
show dev >>> boot -fl "nc" MKA500
In the preceding example, the show dev command provides the device name
under BOOTDEV, and MKA500 is the BOOTDEV.
After the initial boot is complete, the shell invokes the btextract
command. If you created a /usr/lib/sabt/sbin/custom_install.sh script
during the btcreate session, the btextract command invokes the cus‐
tom_install.sh script before exiting. See btcreate for more informa‐
You can optionally label disks using your own disklabel script. If a
customized disk labeling script is not present, the btextract command
labels the disks in the usual manner. A customized disklabel script
has the following restrictions: It must be located in the
/usr/lib/sabt/etc directory. It must be named custom_disklabel_file.
After the btextract command completes, you must shut down the system,
then reboot the system from the restored disk as follows: # shutdown -h
now >>> boot DKA100
In the preceding example, DKA100 is the BOOTDEV.
Creating a Custom Prerestore File
When you boot a system using bootable tape, the btextract command
prompts you to create an answer file that provides the minimum informa‐
tion needed to complete the boot and restore operation. This cus‐
tom_prerestore file is a text file located in the /usr/lib/sabt/etc
directory. The minimum contents are as follows: TDRIVE="tape0_d1"
#Tape drive used RESTORE_TYPE="no" #Restore type yes=DEFAULT
no=ADVANCED SPART="b" #Primary Swap drive partition
You can also create the custom_prerestore file manually, and use it to
fully automate the recovery procedure. The file can contain the follow‐
ing entries: INTERACTIVE=["yes | no"] - Specifies whether the session
is to be interactive or not. A yes entry forces an interactive session.
A typical entry is as follows: INTERACTIVE="no" TDRIVE="device_spe‐
cial_file" - Specifies the device special file name of the tape drive
from which the standalone kernel was booted. A typical entry is as fol‐
lows: TDRIVE="tape0_d1" RESTORE_TYPE=["yes | no"] - Specifies whether
this is to be a default (yes) or an advanced restore (no). A typical
entry is as follows: RESTORE_TYPE="no" SDRIVE="disk_type device name" -
Specifies the primary swap disk drive. This entry requires the follow‐
ing parameters: disk_type - The disk device model, such as HB00931B93 .
You can obtain this information by using the following command: # hwmgr
-show component | grep iomap
The hardware identifier is shown under the HWID column in the
command output. You use this information to determine the device
name of a disk. device name - The device instance, such as
dsk8. This information is part of the device special file name
assigned to the disk. You can obtain this information by using
the following command: # hwmgr -show scsi
SCSI DEVICE DEVICE DRIVER NUM DEVICE
FIRST HWID: DEVICEID HOSTNAME TYPE SUBTYPE OWNER PATH FILE
32: 0 cymro disk none 2 1 dsk0
In the preceding command output, the entry under the HWID column
identifies the disk that you chose by using the show component
option. The HWID is 32 in this example.
A typical entry is as follows: SDRIVE="HB00931B93 dsk13"
SPART="partition_id" - Specifies the primary swap partition on
the restored disk. A typical entry is as follows: SPART="b"
DDRIVE_1="disk_type device name" - Specifies the root file sys‐
tem disk drive. A typical entry is as follows: DDRIVE_1="RZ1CB-
CS dsk13" PPART_1="partition_id" - Specifies the root file sys‐
tem partition. A typical entry is as follows: PPART="a"
DDRIVE_2="disk_type device name" - Specifies the disk drive used
for the /usr file system. A typical entry is as follows:
DDRIVE_2="HB00931B93 dsk11" PPART_1="partition_id" - Specifies
the /usr file system partition. A typical entry is as follows:
PPART="g" DDRIVE_N="disk_type device name" Specifies the disks
used for each additional file system that is restored, where N
is an integer ranging from 3 to the total number of file systems
to be restored. Use entries similar to the following:
DDRIVE_3="HB00931B93 dsk12" PPART_N="partition_id " Specifies
the partitions used for each additional file system that is
restored, where N is an integer ranging from 3 to the total num‐
ber of file systems to be restored. Use entries similar to the
To insert comments in the custom prerestore file, preceded each comment
line with the number symbol (#).
Success. An error occurred.
Log of the btextract process in memory Copy of the btextract process on
the restored root file system Script used to customize the restored
image A custom disklabel file read by btextractSEE ALSO
Commands: addvol(8), btcreate(8), df(1), disklabel(8), lmf(8),
mkfdmn(8), mkfset(8), newfs(8), restore(8), sh(1), vrestore(8)btextract(8)