mkfs.ocfs2 man page on Oracle

mkfs.ocfs2 man page on Oracle

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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 deter‐
mined 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 compat‐
ible 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 lim‐
its 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 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 rela‐
tively 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 sys‐
tem 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 clus‐
ters 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 directo‐
ries 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 automati‐
cally 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 direc‐
tories, directory entry lookup perfromance from the
indexed tree is faster then from the legacy direc‐
tory blocks.

discontig-bg
Enables discontiguous block groups. With this fea‐
ture 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 (dis‐
contiguous) 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 com‐
patibility with relatively recent versions of OCFS2.
It currently enables sparse, unwritten inline-data
xattr, indexed-dirs, discontig-bg, refcount and
extended-slotmap.

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 clus‐
ter stacks known to work with OCFS2 are PCMK (Pacemaker) and
CMAN. Once set, OCFS2 will only allow mounting the volume if the
active cluster stack (and 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.

--global-heartbeat
Enable global heartbeat for the O2CB cluster stack. This option
is not required if the O2CB cluster stack with global heartbeat
is online. However, if the cluster stack is not up, then this
option is required as are 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 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@node1 ~]# 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 │
├─────────────────┼───────────┼───────────┤
│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

Version 1.8.0 February 2011 mkfs.ocfs2(8)

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