Provided by: ocfs2-tools_1.6.4-3.1_amd64 
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-features=[no]sparse...] [--fs-feature-level=feature-level] [-T filesystem-type]
[-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 determined based on the expected usage of the file system (see the -T
option). For volumes expected to store large files, like database 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
supported:
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 equivalent 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 partition. 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 override individual features set via the --fs-feature-level option. Refer
to the section titled feature compatibility before selecting 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 allocation. 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. This feature is automatically
turned on when needed, thus users have no need to turn this on manually.
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: regular 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.
--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 and xattr. It also enables refcount for the
vmstore volumes.
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
compatible with very recent versions of the OCFS2 kernel module.
--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.
-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 that of
the file system for the Enterprise Linux Distributions. 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 │ Mainline Kernel Version │ Enterprise OCFS2 Version │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│local │ Linux 2.6.20 │ OCFS2 1.2 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│sparse │ Linux 2.6.22 │ OCFS2 1.4 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│unwritten │ Linux 2.6.23 │ OCFS2 1.4 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│inline-data │ Linux 2.6.24 │ OCFS2 1.4 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│extended-slotmap │ Linux 2.6.27 │ OCFS2 1.6 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│metaecc │ Linux 2.6.29 │ OCFS2 1.6 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│grpquota │ Linux 2.6.29 │ OCFS2 1.6 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│usrquota │ Linux 2.6.29 │ OCFS2 1.6 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│xattr │ Linux 2.6.29 │ OCFS2 1.6 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│indexed-dirs │ Linux 2.6.30 │ OCFS2 1.6 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│refcount │ Linux 2.6.32 │ OCFS2 1.6 │
├─────────────────┼─────────────────────────┼──────────────────────────┤
│discontig-bg │ Linux 2.6.35 │ OCFS2 1.6 │
└─────────────────┴─────────────────────────┴──────────────────────────┘
Users can query the features enabled in the file system as follows:
[root@node ~]# 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 failures 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) feature 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 feature enabled. This volume can be
mounted by an older file system software 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 │
├─────────────────┼───────────┼───────────┤
│unwritten │ RO Compat │ 1 │
├─────────────────┼───────────┼───────────┤
│usrquota │ RO Compat │ 2 │
├─────────────────┼───────────┼───────────┤
│grpquota │ RO Compat │ 4 │
└─────────────────┴───────────┴───────────┘
SEE ALSO
debugfs.ocfs2(8) fsck.ocfs2(8) tunefs.ocfs2(8) mounted.ocfs2(8) ocfs2console(8) o2cb(7)
AUTHORS
Oracle Corporation
COPYRIGHT
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