quotactl(2) System Calls Manual quotactl(2)
NAME
quotactl - manipulate disk quotas
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <sys/quota.h>
#include <xfs/xqm.h> /* Definition of Q_X* and XFS_QUOTA_* constants
(or <linux/dqblk_xfs.h>; see NOTES) */
int quotactl(int op, const char *_Nullable special, int id,
caddr_t addr);
DESCRIPTION
The quota system can be used to set per-user, per-group, and per-project
limits on the amount of disk space used on a filesystem. For each user
and/or group, a soft limit and a hard limit can be set for each filesys-
tem. The hard limit can't be exceeded. The soft limit can be exceeded,
but warnings will ensue. Moreover, the user can't exceed the soft limit
for more than grace period duration (one week by default) at a time; af-
ter this, the soft limit counts as a hard limit.
The quotactl() call manipulates disk quotas. The op argument indicates
an operation to be applied to the user or group ID specified in id. To
initialize the op argument, use the QCMD(subop, type) macro. The type
value is either USRQUOTA, for user quotas, GRPQUOTA, for group quotas,
or (since Linux 4.1) PRJQUOTA, for project quotas. The subop value is
described below.
The special argument is a pointer to a null-terminated string containing
the pathname of the (mounted) block special device for the filesystem
being manipulated.
The addr argument is the address of an optional, operation-specific,
data structure that is copied in or out of the system. The interpreta-
tion of addr is given with each operation below.
The subop value is one of the following operations:
Q_QUOTAON
Turn on quotas for a filesystem. The id argument is the identi-
fication number of the quota format to be used. Currently, there
are three supported quota formats:
QFMT_VFS_OLD The original quota format.
QFMT_VFS_V0 The standard VFS v0 quota format, which can handle
32-bit UIDs and GIDs and quota limits up to 2^42
bytes and 2^32 inodes.
QFMT_VFS_V1 A quota format that can handle 32-bit UIDs and GIDs
and quota limits of 2^63 - 1 bytes and 2^63 - 1 in-
odes.
The addr argument points to the pathname of a file containing the
quotas for the filesystem. The quota file must exist; it is nor-
mally created with the quotacheck(8) program
Quota information can be also stored in hidden system inodes for
ext4, XFS, and other filesystems if the filesystem is configured
so. In this case, there are no visible quota files and there is
no need to use quotacheck(8). Quota information is always kept
consistent by the filesystem and the Q_QUOTAON operation serves
only to enable enforcement of quota limits. The presence of hid-
den system inodes with quota information is indicated by the
DQF_SYS_FILE flag in the dqi_flags field returned by the Q_GET-
INFO operation.
This operation requires privilege (CAP_SYS_ADMIN).
Q_QUOTAOFF
Turn off quotas for a filesystem. The addr and id arguments are
ignored. This operation requires privilege (CAP_SYS_ADMIN).
Q_GETQUOTA
Get disk quota limits and current usage for user or group id.
The addr argument is a pointer to a dqblk structure defined in
<sys/quota.h> as follows:
/* uint64_t is an unsigned 64-bit integer;
uint32_t is an unsigned 32-bit integer */
struct dqblk { /* Definition since Linux 2.4.22 */
uint64_t dqb_bhardlimit; /* Absolute limit on disk
quota blocks alloc */
uint64_t dqb_bsoftlimit; /* Preferred limit on
disk quota blocks */
uint64_t dqb_curspace; /* Current occupied space
(in bytes) */
uint64_t dqb_ihardlimit; /* Maximum number of
allocated inodes */
uint64_t dqb_isoftlimit; /* Preferred inode limit */
uint64_t dqb_curinodes; /* Current number of
allocated inodes */
uint64_t dqb_btime; /* Time limit for excessive
disk use */
uint64_t dqb_itime; /* Time limit for excessive
files */
uint32_t dqb_valid; /* Bit mask of QIF_*
constants */
};
/* Flags in dqb_valid that indicate which fields in
dqblk structure are valid. */
#define QIF_BLIMITS 1
#define QIF_SPACE 2
#define QIF_ILIMITS 4
#define QIF_INODES 8
#define QIF_BTIME 16
#define QIF_ITIME 32
#define QIF_LIMITS (QIF_BLIMITS | QIF_ILIMITS)
#define QIF_USAGE (QIF_SPACE | QIF_INODES)
#define QIF_TIMES (QIF_BTIME | QIF_ITIME)
#define QIF_ALL (QIF_LIMITS | QIF_USAGE | QIF_TIMES)
The dqb_valid field is a bit mask that is set to indicate the en-
tries in the dqblk structure that are valid. Currently, the ker-
nel fills in all entries of the dqblk structure and marks them as
valid in the dqb_valid field. Unprivileged users may retrieve
only their own quotas; a privileged user (CAP_SYS_ADMIN) can re-
trieve the quotas of any user.
Q_GETNEXTQUOTA (since Linux 4.6)
This operation is the same as Q_GETQUOTA, but it returns quota
information for the next ID greater than or equal to id that has
a quota set.
The addr argument is a pointer to a nextdqblk structure whose
fields are as for the dqblk, except for the addition of a dqb_id
field that is used to return the ID for which quota information
is being returned:
struct nextdqblk {
uint64_t dqb_bhardlimit;
uint64_t dqb_bsoftlimit;
uint64_t dqb_curspace;
uint64_t dqb_ihardlimit;
uint64_t dqb_isoftlimit;
uint64_t dqb_curinodes;
uint64_t dqb_btime;
uint64_t dqb_itime;
uint32_t dqb_valid;
uint32_t dqb_id;
};
Q_SETQUOTA
Set quota information for user or group id, using the information
supplied in the dqblk structure pointed to by addr. The
dqb_valid field of the dqblk structure indicates which entries in
the structure have been set by the caller. This operation super-
sedes the Q_SETQLIM and Q_SETUSE operations in the previous quota
interfaces. This operation requires privilege (CAP_SYS_ADMIN).
Q_GETINFO (since Linux 2.4.22)
Get information (like grace times) about quotafile. The addr ar-
gument should be a pointer to a dqinfo structure. This structure
is defined in <sys/quota.h> as follows:
/* uint64_t is an unsigned 64-bit integer;
uint32_t is an unsigned 32-bit integer */
struct dqinfo { /* Defined since Linux 2.4.22 */
uint64_t dqi_bgrace; /* Time before block soft limit
becomes hard limit */
uint64_t dqi_igrace; /* Time before inode soft limit
becomes hard limit */
uint32_t dqi_flags; /* Flags for quotafile
(DQF_*) */
uint32_t dqi_valid;
};
/* Bits for dqi_flags */
/* Quota format QFMT_VFS_OLD */
#define DQF_ROOT_SQUASH (1 << 0) /* Root squash enabled */
/* Before Linux v4.0, this had been defined
privately as V1_DQF_RSQUASH */
/* Quota format QFMT_VFS_V0 / QFMT_VFS_V1 */
#define DQF_SYS_FILE (1 << 16) /* Quota stored in
a system file */
/* Flags in dqi_valid that indicate which fields in
dqinfo structure are valid. */
#define IIF_BGRACE 1
#define IIF_IGRACE 2
#define IIF_FLAGS 4
#define IIF_ALL (IIF_BGRACE | IIF_IGRACE | IIF_FLAGS)
The dqi_valid field in the dqinfo structure indicates the entries
in the structure that are valid. Currently, the kernel fills in
all entries of the dqinfo structure and marks them all as valid
in the dqi_valid field. The id argument is ignored.
Q_SETINFO (since Linux 2.4.22)
Set information about quotafile. The addr argument should be a
pointer to a dqinfo structure. The dqi_valid field of the dqinfo
structure indicates the entries in the structure that have been
set by the caller. This operation supersedes the Q_SETGRACE and
Q_SETFLAGS operations in the previous quota interfaces. The id
argument is ignored. This operation requires privilege
(CAP_SYS_ADMIN).
Q_GETFMT (since Linux 2.4.22)
Get quota format used on the specified filesystem. The addr ar-
gument should be a pointer to a 4-byte buffer where the format
number will be stored.
Q_SYNC Update the on-disk copy of quota usages for a filesystem. If
special is NULL, then all filesystems with active quotas are
sync'ed. The addr and id arguments are ignored.
Q_GETSTATS (supported up to Linux 2.4.21)
Get statistics and other generic information about the quota sub-
system. The addr argument should be a pointer to a dqstats
structure in which data should be stored. This structure is de-
fined in <sys/quota.h>. The special and id arguments are ig-
nored.
This operation is obsolete and was removed in Linux 2.4.22.
Files in /proc/sys/fs/quota/ carry the information instead.
For XFS filesystems making use of the XFS Quota Manager (XQM), the above
operations are bypassed and the following operations are used:
Q_XQUOTAON
Turn on quotas for an XFS filesystem. XFS provides the ability
to turn on/off quota limit enforcement with quota accounting.
Therefore, XFS expects addr to be a pointer to an unsigned int
that contains a bitwise combination of the following flags (de-
fined in <xfs/xqm.h>):
XFS_QUOTA_UDQ_ACCT /* User quota accounting */
XFS_QUOTA_UDQ_ENFD /* User quota limits enforcement */
XFS_QUOTA_GDQ_ACCT /* Group quota accounting */
XFS_QUOTA_GDQ_ENFD /* Group quota limits enforcement */
XFS_QUOTA_PDQ_ACCT /* Project quota accounting */
XFS_QUOTA_PDQ_ENFD /* Project quota limits enforcement */
This operation requires privilege (CAP_SYS_ADMIN). The id argu-
ment is ignored.
Q_XQUOTAOFF
Turn off quotas for an XFS filesystem. As with Q_QUOTAON, XFS
filesystems expect a pointer to an unsigned int that specifies
whether quota accounting and/or limit enforcement need to be
turned off (using the same flags as for Q_XQUOTAON operation).
This operation requires privilege (CAP_SYS_ADMIN). The id argu-
ment is ignored.
Q_XGETQUOTA
Get disk quota limits and current usage for user id. The addr
argument is a pointer to an fs_disk_quota structure, which is de-
fined in <xfs/xqm.h> as follows:
/* All the blk units are in BBs (Basic Blocks) of
512 bytes. */
#define FS_DQUOT_VERSION 1 /* fs_disk_quota.d_version */
#define XFS_USER_QUOTA (1<<0) /* User quota type */
#define XFS_PROJ_QUOTA (1<<1) /* Project quota type */
#define XFS_GROUP_QUOTA (1<<2) /* Group quota type */
struct fs_disk_quota {
int8_t d_version; /* Version of this structure */
int8_t d_flags; /* XFS_{USER,PROJ,GROUP}_QUOTA */
uint16_t d_fieldmask; /* Field specifier */
uint32_t d_id; /* User, project, or group ID */
uint64_t d_blk_hardlimit; /* Absolute limit on
disk blocks */
uint64_t d_blk_softlimit; /* Preferred limit on
disk blocks */
uint64_t d_ino_hardlimit; /* Maximum # allocated
inodes */
uint64_t d_ino_softlimit; /* Preferred inode limit */
uint64_t d_bcount; /* # disk blocks owned by
the user */
uint64_t d_icount; /* # inodes owned by the user */
int32_t d_itimer; /* Zero if within inode limits */
/* If not, we refuse service */
int32_t d_btimer; /* Similar to above; for
disk blocks */
uint16_t d_iwarns; /* # warnings issued with
respect to # of inodes */
uint16_t d_bwarns; /* # warnings issued with
respect to disk blocks */
int32_t d_padding2; /* Padding - for future use */
uint64_t d_rtb_hardlimit; /* Absolute limit on realtime
(RT) disk blocks */
uint64_t d_rtb_softlimit; /* Preferred limit on RT
disk blocks */
uint64_t d_rtbcount; /* # realtime blocks owned */
int32_t d_rtbtimer; /* Similar to above; for RT
disk blocks */
uint16_t d_rtbwarns; /* # warnings issued with
respect to RT disk blocks */
int16_t d_padding3; /* Padding - for future use */
char d_padding4[8]; /* Yet more padding */
};
Unprivileged users may retrieve only their own quotas; a privi-
leged user (CAP_SYS_ADMIN) may retrieve the quotas of any user.
Q_XGETNEXTQUOTA (since Linux 4.6)
This operation is the same as Q_XGETQUOTA, but it returns (in the
fs_disk_quota structure pointed by addr) quota information for
the next ID greater than or equal to id that has a quota set.
Note that since fs_disk_quota already has q_id field, no separate
structure type is needed (in contrast with Q_GETQUOTA and Q_GET-
NEXTQUOTA operations)
Q_XSETQLIM
Set disk quota limits for user id. The addr argument is a
pointer to an fs_disk_quota structure. This operation requires
privilege (CAP_SYS_ADMIN).
Q_XGETQSTAT
Returns XFS filesystem-specific quota information in the
fs_quota_stat structure pointed by addr. This is useful for
finding out how much space is used to store quota information,
and also to get the quota on/off status of a given local XFS
filesystem. The fs_quota_stat structure itself is defined as
follows:
#define FS_QSTAT_VERSION 1 /* fs_quota_stat.qs_version */
struct fs_qfilestat {
uint64_t qfs_ino; /* Inode number */
uint64_t qfs_nblks; /* Number of BBs
512-byte-blocks */
uint32_t qfs_nextents; /* Number of extents */
};
struct fs_quota_stat {
int8_t qs_version; /* Version number for
future changes */
uint16_t qs_flags; /* XFS_QUOTA_{U,P,G}DQ_{ACCT,ENFD} */
int8_t qs_pad; /* Unused */
struct fs_qfilestat qs_uquota; /* User quota storage
information */
struct fs_qfilestat qs_gquota; /* Group quota storage
information */
uint32_t qs_incoredqs; /* Number of dquots in core */
int32_t qs_btimelimit; /* Limit for blocks timer */
int32_t qs_itimelimit; /* Limit for inodes timer */
int32_t qs_rtbtimelimit;/* Limit for RT
blocks timer */
uint16_t qs_bwarnlimit; /* Limit for # of warnings */
uint16_t qs_iwarnlimit; /* Limit for # of warnings */
};
The id argument is ignored.
Q_XGETQSTATV
Returns XFS filesystem-specific quota information in the
fs_quota_statv pointed to by addr. This version of the operation
uses a structure with proper versioning support, along with ap-
propriate layout (all fields are naturally aligned) and padding
to avoiding special compat handling; it also provides the ability
to get statistics regarding the project quota file. The
fs_quota_statv structure itself is defined as follows:
#define FS_QSTATV_VERSION1 1 /* fs_quota_statv.qs_version */
struct fs_qfilestatv {
uint64_t qfs_ino; /* Inode number */
uint64_t qfs_nblks; /* Number of BBs
512-byte-blocks */
uint32_t qfs_nextents; /* Number of extents */
uint32_t qfs_pad; /* Pad for 8-byte alignment */
};
struct fs_quota_statv {
int8_t qs_version; /* Version for future
changes */
uint8_t qs_pad1; /* Pad for 16-bit alignment */
uint16_t qs_flags; /* XFS_QUOTA_.* flags */
uint32_t qs_incoredqs; /* Number of dquots incore */
struct fs_qfilestatv qs_uquota; /* User quota
information */
struct fs_qfilestatv qs_gquota; /* Group quota
information */
struct fs_qfilestatv qs_pquota; /* Project quota
information */
int32_t qs_btimelimit; /* Limit for blocks timer */
int32_t qs_itimelimit; /* Limit for inodes timer */
int32_t qs_rtbtimelimit; /* Limit for RT blocks
timer */
uint16_t qs_bwarnlimit; /* Limit for # of warnings */
uint16_t qs_iwarnlimit; /* Limit for # of warnings */
uint64_t qs_pad2[8]; /* For future proofing */
};
The qs_version field of the structure should be filled with the
version of the structure supported by the callee (for now, only
FS_QSTAT_VERSION1 is supported). The kernel will fill the struc-
ture in accordance with version provided. The id argument is ig-
nored.
Q_XQUOTARM (buggy until Linux 3.16)
Free the disk space taken by disk quotas. The addr argument
should be a pointer to an unsigned int value containing flags
(the same as in d_flags field of fs_disk_quota structure) which
identify what types of quota should be removed. (Note that the
quota type passed in the op argument is ignored, but should re-
main valid in order to pass preliminary quotactl syscall handler
checks.)
Quotas must have already been turned off. The id argument is ig-
nored.
Q_XQUOTASYNC (since Linux 2.6.15; no-op since Linux 3.4)
This operation was an XFS quota equivalent to Q_SYNC, but it is
no-op since Linux 3.4, as sync(1) writes quota information to
disk now (in addition to the other filesystem metadata that it
writes out). The special, id and addr arguments are ignored.
RETURN VALUE
On success, quotactl() returns 0; on error -1 is returned, and errno is
set to indicate the error.
ERRORS
EACCES op is Q_QUOTAON, and the quota file pointed to by addr exists,
but is not a regular file or is not on the filesystem pointed to
by special.
EBUSY op is Q_QUOTAON, but another Q_QUOTAON had already been per-
formed.
EFAULT addr or special is invalid.
EINVAL op or type is invalid.
EINVAL op is Q_QUOTAON, but the specified quota file is corrupted.
EINVAL (since Linux 5.5)
op is Q_XQUOTARM, but addr does not point to valid quota types.
ENOENT The file specified by special or addr does not exist.
ENOSYS The kernel has not been compiled with the CONFIG_QUOTA option.
ENOTBLK
special is not a block device.
EPERM The caller lacked the required privilege (CAP_SYS_ADMIN) for the
specified operation.
ERANGE op is Q_SETQUOTA, but the specified limits are out of the range
allowed by the quota format.
ESRCH No disk quota is found for the indicated user. Quotas have not
been turned on for this filesystem.
ESRCH op is Q_QUOTAON, but the specified quota format was not found.
ESRCH op is Q_GETNEXTQUOTA or Q_XGETNEXTQUOTA, but there is no ID
greater than or equal to id that has an active quota.
NOTES
Instead of <xfs/xqm.h> one can use <linux/dqblk_xfs.h>, taking into ac-
count that there are several naming discrepancies:
• Quota enabling flags (of format XFS_QUOTA_[UGP]DQ_{ACCT,ENFD}) are
defined without a leading "X", as FS_QUOTA_[UGP]DQ_{ACCT,ENFD}.
• The same is true for XFS_{USER,GROUP,PROJ}_QUOTA quota type flags,
which are defined as FS_{USER,GROUP,PROJ}_QUOTA.
• The dqblk_xfs.h header file defines its own XQM_USRQUOTA, XQM_GR-
PQUOTA, and XQM_PRJQUOTA constants for the available quota types, but
their values are the same as for constants without the XQM_ prefix.
SEE ALSO
quota(1), getrlimit(2), quotacheck(8), quotaon(8)
Linux man-pages 6.9.1 2024-05-02 quotactl(2)
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