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mkfs.ocfs2(8) OCFS2 Manual Pages mkfs.ocfs2(8)

NAME
mkfs.ocfs2 - Creates an OCFS2 file system.

SYNOPSIS
mkfs.ocfs2 [-b block-size] [-C cluster-size] [-L volume-label] [-M
mount-type] [-N number-of-nodes] [-J journal-options] [--fs-fea‐
tures=[no]sparse...] [--fs-feature-level=feature-level] [-T filesys‐
tem-type] [--cluster-stack=stackname] [--cluster-name=clustername]
[--global-heartbeat] [-FqvV] device [blocks-count]

DESCRIPTION
mkfs.ocfs2 is used to create an OCFS2 file system on a device, usually
a partition on a shared disk. In order to prevent data loss, mkfs.ocfs2
will not format an existing OCFS2 volume if it detects that it is
mounted on another node in the cluster. This tool requires the cluster
service to be online.

OPTIONS
-b, --block-size block-size
Valid block size values are 512, 1K, 2K and 4K bytes per block.
If omitted, a value will be heuristically determined based on
the expected usage of the file system (see the -T option). A
block size of 512 bytes is never recommended. Choose 1K, 2K or
4K.

-C, --cluster-size cluster-size
Valid cluster size values are 4K, 8K, 16K, 32K, 64K, 128K, 256K,
512K and 1M. If omitted, a value will be heuristically deter‐
mined based on the expected usage of the file system (see the -T
option). For volumes expected to store large files, like data‐
base files, while a cluster size of 128K or more is recommended,
one can opt for a smaller size as long as that value is not
smaller than the database block size. For others, use 4K.

-F, --force
For existing OCFS2 volumes, mkfs.ocfs2 ensures the volume is not
mounted on any node in the cluster before formatting. For that
to work, mkfs.ocfs2 expects the cluster service to be online.
Specify this option to disable this check.

-J, --journal-options options
Create the journal using options specified on the command-line.
Journal options are comma separated, and may take an argument
using the equals ('=') sign. The following options are sup‐
ported:

size=journal-size
Create a journal of size journal-size. Minimum size is
4M. If omitted, a value is heuristically determined
based upon the file system size.

block32
Use a standard 32bit journal. The journal will be able
to access up to 2^32-1 blocks. This is the default. It
has been the journal format for OCFS2 volumes since the
beginning. The journal is compatible with all versions
of OCFS2. Prepending no is equivalent to the block64
journal option.

block64
Use a 64bit journal. The journal will be able to access
up to 2^64-1 blocks. This allows large filesystems that
can extend to the theoretical limits of OCFS2. It
requires a new-enough filesystem driver that uses the new
journalled block device, JBD2. Prepending no is equiva‐
lent to the block32 journal option.

-L, --label volume-label
Set the volume label for the file system. This is useful for
mounting-by-label. Limit the label to under 64 bytes.

-M, --mount mount-type
Valid types are local and cluster. Local mount allows users to
mount the volume without the cluster overhead and works only
with OCFS2 bundled with Linux kernels 2.6.20 or later. Defaults
to cluster.

-N, --node-slots number-of-node-slots
Valid number ranges from 1 to 255. This number specifies the
maximum number of nodes that can concurrently mount the parti‐
tion. If omitted, the number defaults to 8. The number of slots
can be later tuned up or down using tunefs.ocfs2.

-T filesystem-type
Specify how the filesystem is going to be used, so that
mkfs.ocfs2 can chose optimal filesystem parameters for that use.
The supported filesystem types are:

mail Appropriate for file systems that will host lots of small
files.

datafiles
Appropriate for file systems that will host a relatively
small number of very large files.

vmstore
Appropriate for file systems that will host Virtual
machine images.

--fs-features=[no]sparse...
Turn specific file system features on or off. A comma separated
list of feature flags can be provided, and mkfs.ocfs2 will try
to create the file system with those features set according to
the list. To turn a feature on, include it in the list. To turn
a feature off, prepend no to the name. Choices here will over‐
ride individual features set via the --fs-feature-level option.
Refer to the section titled feature compatibility before select‐
ing specific features. The following flags are supported:

backup-super
mkfs.ocfs2, by default, makes up to 6 backup copies of
the super block at offsets 1G, 4G, 16G, 64G, 256G and 1T
depending on the size of the volume. This can be useful
in disaster recovery. This feature is fully compatible
with all versions of the file system and generally should
not be disabled.

local Create the file system as a local mount, so that it can
be mounted without a cluster stack.

sparse Enable support for sparse files. With this, OCFS2 can
avoid allocating (and zeroing) data to fill holes. Turn
this feature on if you can, otherwise extends and some
writes might be less performant.

unwritten
Enable unwritten extents support. With this turned on, an
application can request that a range of clusters be pre-
allocated within a file. OCFS2 will mark those extents
with a special flag so that expensive data zeroing
doesn't have to be performed. Reads and writes to a pre-
allocated region act as reads and writes to a hole,
except a write will not fail due to lack of data alloca‐
tion. This feature requires sparse file support to be
turned on.

inline-data
Enable inline-data support. If this feature is turned on,
OCFS2 will store small files and directories inside the
inode block. Data is transparently moved out to an extent
when it no longer fits inside the inode block. In some
cases, this can also make a positive impact on cold-cache
directory and file operations.

extended-slotmap
The slot-map is a hidden file on an OCFS2 fs which is
used to map mounted nodes to system file resources. The
extended slot map allows a larger range of possible node
numbers, which is useful for userspace cluster stacks. If
required, this feature is automatically turned on by
mkfs.ocfs2.

metaecc
Enables metadata checksums. With this enabled, the file
system computes and stores the checksums in all metadata
blocks. It also computes and stores an error correction
code capable of fixing single bit errors.

refcount
Enables creation of reference counted trees. With this
enabled, the file system allows users to create inode-
based snapshots and clones known as reflinks.

xattr Enable extended attributes support. With this enabled,
users can attach name:value pairs to objects within the
file system. In OCFS2, the names can be upto 255 bytes in
length, terminated by the first NUL byte. While it is not
required, printable names (ASCII) are recommended. The
values can be upto 64KB of arbitrary binary data.
Attributes can be attached to all types of inodes: regu‐
lar files, directories, symbolic links, device nodes,
etc. This feature is required for users wanting to use
extended security facilities like POSIX ACLs or SELinux.

usrquota
Enable user quota support. With this feature enabled,
filesystem will track amount of space and number of
inodes (files, directories, symbolic links) each user
owns. It is then possible to limit the maximum amount of
space or inodes user can have. See a documentation of
quota-tools package for more details.

grpquota
Enable group quota support. With this feature enabled,
filesystem will track amount of space and number of
inodes (files, directories, symbolic links) each group
owns. It is then possible to limit the maximum amount of
space or inodes user can have. See a documentation of
quota-tools package for more details.

indexed-dirs
Enable directory indexing support. With this feature
enabled, the file system creates indexed tree for non-
inline directory entries. For large scale directories,
directory entry lookup perfromance from the indexed tree
is faster then from the legacy directory blocks.

discontig-bg
Enables discontiguous block groups. With this feature
enabled, the file system is able to grow the inode and
the extent allocators even when there is no contiguous
free chunk available. It allows the file system to grow
the allocators in smaller (discontiguous) chunks.

clusterinfo
Enables storing the cluster stack information in the
superblock. This feature is needed to support userspace
cluster stacks and the global heartbeat mode in the o2cb
cluster stack. If needed, this feature is automatically
turned on by mkfs.ocfs2.

--fs-feature-level=feature-level
Choose from a set of pre-determined file-system features. This
option is designed to allow users to conveniently choose a set
of file system features which fits their needs. There is no
downside to trying a set of features which your module might not
support - if it won't mount the new file system simply reformat
at a lower level. Feature levels can be fine-tuned via the
--fs-features option. Currently, there are 3 types of feature
levels:

max-compat
Chooses fewer features but ensures that the file system
can be mounted from older versions of the OCFS2 module.

default
The default feature set tries to strike a balance between
providing new features and maintaining compatibility with
relatively recent versions of OCFS2. It currently enables
sparse, unwritten, inline-data, xattr, indexed-dirs, dis‐
contig-bg, refcount, extended-slotmap and clusterinfo.

max-features
Choose the maximum amount of features available. This
will typically provide the best performance from OCFS2 at
the expense of creating a file system that is only com‐
patible with very recent versions of the OCFS2 kernel
module.

--cluster-stack
Specify the cluster stack. This option is normally not required
as mkfs.ocfs2 chooses the currently active cluster stack. It is
required only if the cluster stack is not online and the user
wishes to use a stack other than the default, o2cb. Other sup‐
ported cluster stacks are pcmk (Pacemaker) and cman (rgmanager).
Once set, OCFS2 will only allow mounting the volume if the
active cluster stack and cluster name matches the one specified
on-disk.

--cluster-name
Specify the name of the cluster. This option is mandatory if the
user has specified a cluster-stack. This name is restricted to a
max of 16 characters. Additionally, the o2cb cluster stack
allows only alpha-numeric characters.

--global-heartbeat
Enable the global heartbeat mode of the o2cb cluster stack. This
option is not required if the o2cb cluster stack with global
heartbeat is online as mkfs.ocfs2 will detect the active stack.
However, if the cluster stack is not up, then this option is
required alongwith cluster-stack and cluster-name. For more,
refer to o2cb(7).

--no-backup-super
This option is deprecated, please use --fs-features=nobackup-
super instead.

-n, --dry-run
Display the heuristically determined values without overwriting
the existing file system.

-q, --quiet
Quiet mode.

-U uuid
Specify a custom UUID in the plain
(2A4D1C581FAA42A1A41D26EFC90C1315) or traditional
(2a4d1c58-1faa-42a1-a41d-26efc90c1315) format. This option in
not recommended because the file system uses the UUID to
uniquely identify a file system. If more than one file system
were to have the same UUID, one is very likely to encounter
erratic behavior, if not, outright file system corruption.

-v, --verbose
Verbose mode.

-V, --version
Print version and exit.

blocks-count
Usually mkfs.ocfs2 automatically determines the size of the
given device and creates a file system that uses all of the
available space on the device. This optional argument specifies
that the file system should only consume the given number of
file system blocks (see -b) on the device.

FEATURE COMPATIBILITY
This section lists the file system features that have been added to the
OCFS2 file system and the version that it first appeared in. The table
below lists the versions of the mainline Linux kernel and ocfs2-tools.
Users should use this information to enable only those features that
are available in the file system that they are using. Before enabling
new features, users are advised to review to the section titled feature
values.

┌─────────────────┬────────────────┬─────────────────┐
│Feature │ Kernel Version │ Tools Version │
├─────────────────┼────────────────┼─────────────────┤
│local │ Linux 2.6.20 │ ocfs2-tools 1.2 │
├─────────────────┼────────────────┼─────────────────┤
│sparse │ Linux 2.6.22 │ ocfs2-tools 1.4 │
├─────────────────┼────────────────┼─────────────────┤
│unwritten │ Linux 2.6.23 │ ocfs2-tools 1.4 │
├─────────────────┼────────────────┼─────────────────┤
│inline-data │ Linux 2.6.24 │ ocfs2-tools 1.4 │
├─────────────────┼────────────────┼─────────────────┤
│extended-slotmap │ Linux 2.6.27 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│metaecc │ Linux 2.6.29 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│grpquota │ Linux 2.6.29 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│usrquota │ Linux 2.6.29 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│xattr │ Linux 2.6.29 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│indexed-dirs │ Linux 2.6.30 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│refcount │ Linux 2.6.32 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│discontig-bg │ Linux 2.6.35 │ ocfs2-tools 1.6 │
├─────────────────┼────────────────┼─────────────────┤
│clusterinfo │ Linux 2.6.37 │ ocfs2-tools 1.8 │
└─────────────────┴────────────────┴─────────────────┘

Users can query the features enabled in the file system as follows:

# tunefs.ocfs2 -Q "Label: %V\nFeatures: %H %O\n" /dev/sdg1
Label: apache_files_10
Features: sparse inline-data unwritten

FEATURE VALUES
This section lists the hex values that are associated with the file
system features. This information is useful when debugging mount fail‐
ures that are due to feature incompatibility. When a user attempts to
mount an OCFS2 volume that has features enabled that are not supported
by the running file system software, it will fail with an error like:

ERROR: couldn't mount because of unsupported optional features (200).

By referring to the table below, it becomes apparent that the user
attempted to mount a volume with the xattr (extended attributes) fea‐
ture enabled with a version of the file system software that did not
support it. At this stage, the user has the option of either upgrading
the file system software, or, disabling that on-disk feature using
tunefs.ocfs2.

Some features allow the file system to be mounted with an older version
of the software provided the mount is read-only. If a user attempts to
mount such a volume in a read-write mode, it will fail with an error
like:

ERROR: couldn't mount RDWR because of unsupported optional features (1).

This error indicates that the volume had the unwritten RO compat fea‐
ture enabled. This volume can be mounted by an older file system soft‐
ware only in the read-only mode. In this case, the user has the option
of either mounting the volume with the ro mount option, or, disabling
that on-disk feature using tunefs.ocfs2.

┌─────────────────┬───────────┬───────────┐
│Feature │ Category │ Hex value │
├─────────────────┼───────────┼───────────┤
│local │ Incompat │ 8 │
├─────────────────┼───────────┼───────────┤
│sparse │ Incompat │ 10 │
├─────────────────┼───────────┼───────────┤
│inline-data │ Incompat │ 40 │
├─────────────────┼───────────┼───────────┤
│extended-slotmap │ Incompat │ 100 │
├─────────────────┼───────────┼───────────┤
│xattr │ Incompat │ 200 │
├─────────────────┼───────────┼───────────┤
│indexed-dirs │ Incompat │ 400 │
├─────────────────┼───────────┼───────────┤
│metaecc │ Incompat │ 800 │
├─────────────────┼───────────┼───────────┤
│refcount │ Incompat │ 1000 │
├─────────────────┼───────────┼───────────┤
│discontig-bg │ Incompat │ 2000 │
├─────────────────┼───────────┼───────────┤
│clusterinfo │ Incompat │ 4000 │
├─────────────────┼───────────┼───────────┤
│unwritten │ RO Compat │ 1 │
├─────────────────┼───────────┼───────────┤
│usrquota │ RO Compat │ 2 │
├─────────────────┼───────────┼───────────┤
│grpquota │ RO Compat │ 4 │
└─────────────────┴───────────┴───────────┘

SEE ALSO
debugfs.ocfs2(8) fsck.ocfs2(8) mount.ocfs2(8) mounted.ocfs2(8) o2cb(7)
o2cluster(8) o2image(8) o2info(1) tunefs.ocfs2(8)

AUTHORS
Oracle Corporation

Version 1.8.2 January 2012 mkfs.ocfs2(8)

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