Provided by: ocfs2-tools_1.8.7-1build4_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] [--cluster-stack=stackname]
[--cluster-name=clustername] [--global-heartbeat] [--discard | --nodiscard] [-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 depends on
volume size, for volume size < 2G, it's 2, for 2G <= size < 10G, it's 4, for 10G <=
size < 1T, it's 8, for other size, it's 16. 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. 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 up to 255 bytes in length, terminated by the first NUL byte. While it is
not required, printable names (ASCII) are recommended. The values can be up
to 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 performance 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, discontig-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 compatible 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 supported 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).
--discard
Attempt to discard blocks at mkfs time (discarding blocks initially is useful on
solid state devices and sparse / thin-provisioned storage). When the device
advertises that discard also zeroes data (any subsequent read after the discard and
before write returns zero), then mark all not-yet-zeroed blocks as zeroed. This
significantly speeds up filesystem initialization. This is set as default.
--nodiscard
Do not attempt to discard blocks at mkfs time.
--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 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 │
├─────────────────┼───────────┼───────────┤
│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
COPYRIGHT
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