xfs_quota(8) - man - phpMan

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xfs_quota(8) System Manager's Manual xfs_quota(8)

NAME
xfs_quota - manage use of quota on XFS filesystems

SYNOPSIS
xfs_quota [ -x ] [ -f ] [ -p prog ] [ -c cmd ] ... [ -d project ] ... [ -D projects_file ] [
-P projid_file ] [ path ... ]
xfs_quota -V

DESCRIPTION
xfs_quota is a utility for reporting and editing various aspects of filesystem quota.

The options to xfs_quota are:

-c cmd xfs_quota commands may be run interactively (the default) or as arguments on the
command line. Multiple -c arguments may be given. The commands are run in the se‐
quence given, then the program exits.

-p prog Set the program name for prompts and some error messages, the default value is
xfs_quota.

-x Enable expert mode. All of the administrative commands (see the ADMINISTRATOR COM‐
MANDS section below) which allow modifications to the quota system are available
only in expert mode.

-f Enable foreign filesystem mode. A limited number of user and administrative com‐
mands are available for use on some foreign (non-XFS) filesystems.

-d project
Project names or numeric identifiers may be specified with this option, which re‐
stricts the output of the individual xfs_quota commands to the set of projects
specified. Multiple -d arguments may be given.

-D projects_file
Specify a file containing the mapping of numeric project identifiers to directory
trees. /etc/projects as default, if this option is none.

-P projid_file
Specify a file containing the mapping of numeric project identifiers to project
names. /etc/projid as default, if this option is none.

-V Prints the version number and exits.

The optional path argument(s) can be used to specify mount points or device files which iden‐
tify XFS filesystems. The output of the individual xfs_quota commands will then be restricted
to the set of filesystems specified.

This manual page is divided into two sections - firstly, information for users of filesystems
with quota enabled, and the xfs_quota commands of interest to such users; and then informa‐
tion which is useful only to administrators of XFS filesystems using quota and the quota com‐
mands which allow modifications to the quota system.

Note that common to almost all of the individual commands described below are the options for
specifying which quota types are of interest - user quota (-u), group quota (-g), and/or
project quota (-p). Also, several commands provide options to operate on "blocks used" (-b),
"inodes used" (-i), and/or "realtime blocks used" (-r).

Many commands also have extensive online help. Use the help command for more details on any
command.

QUOTA OVERVIEW
In most computing environments, disk space is not infinite. The quota subsystem provides a
mechanism to control usage of disk space. Quotas can be set for each individual user on
any/all of the local filesystems. The quota subsystem warns users when they exceed their al‐
lotted limit, but allows some extra space for current work (hard limit/soft limit). In addi‐
tion, XFS filesystems with limit enforcement turned off can be used as an effective disk us‐
age accounting system.

Users' View of Disk Quotas
To most users, disk quotas are either of no concern or a fact of life that cannot be avoided.
There are two possible quotas that can be imposed - a limit can be set on the amount of space
a user can occupy, and there may be a limit on the number of files (inodes) they can own.

The quota command provides information on the quotas that have been set by the system admin‐
istrators and current usage.

There are four numbers for each limit: current usage, soft limit (quota), hard limit, and
time limit. The soft limit is the number of 1K-blocks (or files) that the user is expected
to remain below. The hard limit cannot be exceeded. If a user's usage reaches the hard
limit, further requests for space (or attempts to create a file) fail with the "Quota ex‐
ceeded" (EDQUOT) error.

When a user exceeds the soft limit, the timer is enabled. Any time the quota drops below the
soft limits, the timer is disabled. If the timer pops, the particular limit that has been
exceeded is treated as if the hard limit has been reached, and no more resources are allo‐
cated to the user. The only way to reset this condition, short of turning off limit enforce‐
ment or increasing the limit, is to reduce usage below quota. Only the superuser (i.e. a
sufficiently capable process) can set the time limits and this is done on a per filesystem
basis.

Surviving When the Quota Limit Is Reached
In most cases, the only way for a user to recover from over-quota conditions is to abort
whatever activity is in progress on the filesystem that has reached its limit, remove suffi‐
cient files to bring the limit back below quota, and retry the failed program.
However, if a user is in the editor and a write fails because of an over quota situation,
that is not a suitable course of action. It is most likely that initially attempting to
write the file has truncated its previous contents, so if the editor is aborted without cor‐
rectly writing the file, not only are the recent changes lost, but possibly much, or even
all, of the contents that previously existed.
There are several possible safe exits for a user caught in this situation. They can use the
editor shell escape command to examine their file space and remove surplus files. Alterna‐
tively, using sh(1), they can suspend the editor, remove some files, then resume it. A third
possibility is to write the file to some other filesystem (perhaps to a file on /tmp) where
the user's quota has not been exceeded. Then after rectifying the quota situation, the file
can be moved back to the filesystem it belongs on.

Default Quotas
The XFS quota subsystem allows a default quota to be enforced for any user, group or project
which does not have a quota limit explicitly set. These limits are stored in and displayed
as ID 0's limits, although they do not actually limit ID 0.

USER COMMANDS
print Lists all paths with devices/project identifiers. The path list can come from several
places - the command line, the mount table, and the /etc/projects file.

df See the free command.

quota [ -g | -p | -u ] [ -bir ] [ -hnNv ] [ -f file ] [ ID | name ] ...
Show individual usage and limits, for a single user name or numeric user ID. The -h
option reports in a "human-readable" format similar to the df(1) command. The -n op‐
tion reports the numeric IDs rather than the name. The -N option omits the header. The
-v option outputs verbose information. The -f option sends the output to file instead
of stdout.

free [ -bir ] [ -hN ] [ -f file ]
Reports filesystem usage, much like the df(1) utility. It can show usage for blocks,
inode, and/or realtime block space, and shows used, free, and total available. If
project quota are in use (see the DIRECTORY TREE QUOTA section below), it will also
report utilisation for those projects (directory trees). The -h option reports in a
"human-readable" format. The -N option omits the header. The -f option outputs the re‐
port to file instead of stdout.

help [ command ]
Online help for all commands, or one specific command.

quit Exit xfs_quota.

q See the quit command.

QUOTA ADMINISTRATION
The XFS quota system differs to that of other filesystems in a number of ways. Most impor‐
tantly, XFS considers quota information as filesystem metadata and uses journaling to provide
a higher level guarantee of consistency. As such, it is administered differently, in partic‐
ular:

1. The quotacheck command has no effect on XFS filesystems. The first time quota ac‐
counting is turned on (at mount time), XFS does an automatic quotacheck internally;
afterwards, the quota system will always be completely consistent until quotas are
manually turned off.

2. There is no need for quota file(s) in the root of the XFS filesystem.

3. XFS distinguishes between quota accounting and limit enforcement. Quota accounting
must be turned on at the time of mounting the XFS filesystem. However, it is possible
to turn on/off limit enforcement any time quota accounting is turned on. The "quota"
option to the mount command turns on both (user) quota accounting and enforcement.
The "uqnoenforce" option must be used to turn on user accounting with limit enforce‐
ment disabled.

4. Turning on quotas on the root filesystem is slightly different from the above. For
Linux XFS, the quota mount flags must be passed in with the "rootflags=" boot parame‐
ter.

5. It is useful to use the state to monitor the XFS quota subsystem at various stages -
it can be used to see if quotas are turned on, and also to monitor the space occupied
by the quota system itself..

6. There is a mechanism built into xfsdump that allows quota limit information to be
backed up for later restoration, should the need arise.

7. Quota limits cannot be set before turning on quotas on.

8. XFS filesystems keep quota accounting on the superuser (user ID zero), and the tool
will display the superuser's usage information. However, limits are never enforced on
the superuser (nor are they enforced for group and project ID zero).

9. XFS filesystems perform quota accounting whether the user has quota limits or not.

10. XFS supports the notion of project quota, which can be used to implement a form of di‐
rectory tree quota (i.e. to restrict a directory tree to only being able to use up a
component of the filesystems available space; or simply to keep track of the amount of
space used, or number of inodes, within the tree).

ADMINISTRATOR COMMANDS
path [ N ]
Lists all paths with devices/project identifiers or set the current path to the Nth
list entry (the current path is used by many of the commands described here, it iden‐
tifies the filesystem toward which a command is directed). The path list can come
from several places - the command line, the mount table, and the /etc/projects file.

report [ -gpu ] [ -bir ] [ -ahntlLNU ] [ -f file ]
Report filesystem quota information. This reports all quota usage for a filesystem,
for the specified quota type (u/g/p and/or blocks/inodes/realtime). It reports blocks
in 1KB units by default. The -h option reports in a "human-readable" format similar to
the df(1) command. The -f option outputs the report to file instead of stdout. The -a
option reports on all filesystems. By default, outputs the name of the
user/group/project. If no name is defined for a given ID, outputs the numeric ID in‐
stead. The -n option outputs the numeric ID instead of the name. The -L and -U options
specify lower and upper ID bounds to report on. If upper/lower bounds are specified,
then by default only the IDs will be displayed in output; with the -l option, a lookup
will be performed to translate these IDs to names. The -N option reports information
without the header line. The -t option performs a terse report.

state [ -gpu ] [ -av ] [ -f file ]
Report overall quota state information. This reports on the state of quota account‐
ing, quota enforcement, and the number of extents being used by quota metadata within
the filesystem. The -f option outputs state information to file instead of stdout. The
-a option reports state on all filesystems and not just the current path.

timer [ -g | -p | -u ] [ -bir ] value [ -d | id | name ]
Allows the quota enforcement timeout (i.e. the amount of time allowed to pass before
the soft limits are enforced as the hard limits) to be modified. The current timeout
setting can be displayed using the state command.
When setting the default timer via the -d option, or for id 0, or if no argument is
given after value the value argument is a number of seconds indicating the relative
amount of time after soft limits are exceeded, before hard limits are enforced.
When setting any other individual timer by id or name, the value is the number of sec‐
onds from now, at which time the hard limits will be enforced. This allows extending
the grace time of an individual user who has exceeded soft limits.
For value, units of 'minutes', 'hours', 'days', and 'weeks' are also understood (as
are their abbreviations 'm', 'h', 'd', and 'w').

warn [ -g | -p | -u ] [ -bir ] value -d | id | name
Allows the quota warnings limit (i.e. the number of times a warning will be send to
someone over quota) to be viewed and modified. The -d option (defaults) can be used to
set the default time that will be used, otherwise a specific user/group/project name
or numeric identifier must be specified. NOTE: this feature is not currently imple‐‐
mented.

enable [ -gpu ] [ -v ]
Switches on quota enforcement for the filesystem identified by the current path. This
requires the filesystem to have been mounted with quota enabled, and for accounting to
be currently active. The -v option (verbose) displays the state after the operation
has completed.

disable [ -gpu ] [ -v ]
Disables quota enforcement, while leaving quota accounting active. The -v option (ver‐
bose) displays the state after the operation has completed.

off [ -gpu ] [ -v ]
Permanently switches quota off for the filesystem identified by the current path.
Quota can only be switched back on subsequently by unmounting and then mounting again.

remove [ -gpu ] [ -v ]
Remove any space allocated to quota metadata from the filesystem identified by the
current path. Quota must not be enabled on the filesystem, else this operation will
report an error.

dump [ -g | -p | -u ] [ -f file ]
Dump out quota limit information for backup utilities, either to standard output (de‐
fault) or to a file. This is only the limits, not the usage information, of course.

restore [ -g | -p | -u ] [ -f file ]
Restore quota limits from a backup file. The file must be in the format produced by
the dump command.

quot [ -g | -p | -u ] [ -bir ] [ -acnv ] [ -f file ]
Summarize filesystem ownership, by user, group or project. This command uses a spe‐
cial XFS "bulkstat" interface to quickly scan an entire filesystem and report usage
information. This command can be used even when filesystem quota are not enabled, as
it is a full-filesystem scan (it may also take a long time...). The -a option displays
information on all filesystems. The -c option displays a histogram instead of a re‐
port. The -n option displays numeric IDs rather than names. The -v option displays
verbose information. The -f option send the output to file instead of stdout.

project [ -cCs [ -d depth ] [ -p path ] id | name ]
The -c, -C, and -s options allow the directory tree quota mechanism to be maintained.
-d allows one to limit recursion level when processing project directories and -p al‐
lows one to specify project paths at command line ( instead of /etc/projects ). All
options are discussed in detail below.

DIRECTORY TREE QUOTA
The project quota mechanism in XFS can be used to implement a form of directory tree quota,
where a specified directory and all of the files and subdirectories below it (i.e. a tree)
can be restricted to using a subset of the available space in the filesystem.

A managed tree must be setup initially using the -s option to the project command. The speci‐
fied project name or identifier is matched to one or more trees defined in /etc/projects, and
these trees are then recursively descended to mark the affected inodes as being part of that
tree. This process sets an inode flag and the project identifier on every file in the af‐
fected tree. Once this has been done, new files created in the tree will automatically be
accounted to the tree based on their project identifier. An attempt to create a hard link to
a file in the tree will only succeed if the project identifier matches the project identifier
for the tree. The xfs_io utility can be used to set the project ID for an arbitrary file,
but this can only be done by a privileged user.

A previously setup tree can be cleared from project quota control through use of the project
-C option, which will recursively descend the tree, clearing the affected inodes from project
quota control.

Finally, the project -c option can be used to check whether a tree is setup, it reports noth‐
ing if the tree is correct, otherwise it reports the paths of inodes which do not have the
project ID of the rest of the tree, or if the inode flag is not set.

Option -d can be used to limit recursion level (-1 is infinite, 0 is top level only, 1 is
first level ... ). Option -p adds possibility to specify project paths in command line with‐
out a need for /etc/projects to exist. Note that if projects file exists then it is also
used.

EXAMPLES
Enabling quota enforcement on an XFS filesystem (restrict a user to a set amount of space).

# mount -o uquota /dev/xvm/home /home
# xfs_quota -x -c 'limit bsoft=500m bhard=550m tanya' /home
# xfs_quota -x -c report /home

Enabling project quota on an XFS filesystem (restrict files in log file directories to only
using 1 gigabyte of space).

# mount -o prjquota /dev/xvm/var /var
# echo 42:/var/log >> /etc/projects
# echo logfiles:42 >> /etc/projid
# xfs_quota -x -c 'project -s logfiles' /var
# xfs_quota -x -c 'limit -p bhard=1g logfiles' /var

Same as above without a need for configuration files.

# rm -f /etc/projects /etc/projid
# mount -o prjquota /dev/xvm/var /var
# xfs_quota -x -c 'project -s -p /var/log 42' /var
# xfs_quota -x -c 'limit -p bhard=1g 42' /var

CAVEATS
The XFS allocation mechanism will always reserve the maximum amount of space required before
proceeding with an allocation. If insufficient space for this reservation is available, due
to the block quota limit being reached for example, this may result in the allocation failing
even though there is sufficient space. Quota enforcement can thus sometimes happen in situa‐
tions where the user is under quota and the end result of some operation would still have
left the user under quota had the operation been allowed to run its course. This additional
overhead is typically in the range of tens of blocks.

Both of these properties are unavoidable side effects of the way XFS operates, so should be
kept in mind when assigning block limits.

BUGS
Quota support for filesystems with realtime subvolumes is not yet implemented, nor is the
quota warning mechanism (the Linux warnquota(8) tool can be used to provide similar function‐
ality on that platform).

FILES
/etc/projects Mapping of numeric project identifiers to directories trees.
/etc/projid Mapping of numeric project identifiers to project names.

SEE ALSO
df(1), mount(1), sync(2), projid(5), projects(5). xfs(5). warnquota(8),

xfs_quota(8)