long quotactl(int cmd, char *special, qid_t id, caddr_t addr)
The quotactl() call manipulates disk quotas. cmd indicates a command to be applied toUID id or GID id. To set the type of quota use the QCMD(cmd, type) macro. special is a pointer to a null-terminated string containing the path name of the block special device for the filesystem being manipulated. addr is the address of an optional, command specific, data structure which is copied in or out of the system. The interpretation of addris given with each command below.
Turn on quotas for a filesystem. id is the identification number of the quota format to be used. Format numbers are defined in the header file of appropriate format. Currently there are two supported quota formats whose numbers are defined by constants QFMT_VFS_OLD (original quota format) andQFMT_VFS_V0 (new VFS v0 quota format). addr points to the path name of file containing the quotas for the filesystem. The quota file must exist; it is normally created with thequotacheck(8) program. This call is restricted to the super-user.
Turn off quotas for a filesystem. addr and id are ignored. This call is restricted to the super-user.
Get disk quota limits and current usage for user or group id. addris a pointer to an if_dqblk structure (defined in<sys/quota.h>). The field dqb_valid defines the entries in the structure which are set correctly. On Q_GETQUOTA call all entries are valid. Only the super-user may get the quotas of a user other than himself.
Set current quota information for user or group id. addr is a pointer to an if_dqblk structure (defined in <sys/quota.h>). The field dqb_valid defines which entries in the quota structure are valid and should be set. The constants for dqb_valid field are defined in the <sys/quota.h> header file. This call obsoletes calls Q_SETQLIM and Q_SETUSE in the previous quota interfaces. This call is restricted to the super-user.
Get information (like grace times) about quotafile. addr should be a pointer to an if_dqinfo structure (defined in<sys/quota.h>). The dqi_valid field in the structure defines entries in it which are valid. On Q_GETINFO call all entries are valid. Parameter id is ignored.
Set information about quotafile. addr should be a pointer toif_dqinfo structure (defined in <sys/quota.h>). The field dqi_validdefines which entries in the quota info structure are valid and should be set. The constants for dqi_valid field are defined in the<sys/quota.h> header file. This call obsoletes callsQ_SETGRACE and Q_SETFLAGS in the previous quota interfaces. Parameter id is ignored. This operation is restricted to super-user.
Get quota format used on the specified filesystem. addr should be a pointer to a memory (4 bytes) where the format number will be stored.
Update the on-disk copy of quota usages for a filesystem. Ifspecial is null then all filesystems with active quotas are sync’ed.addr and id are ignored.
Get statistics and other generic information about quota subsystem. addr should be a pointer to dqstats structure (defined in <sys/quota.h>) in which data should be stored.special and id are ignored.
For XFS filesystems making use of the XFS Quota Manager (XQM), the above commands are bypassed and the following commands 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 the addr to be a pointer to an unsigned int that contains either the flags XFS_QUOTA_UDQ_ACCT and/or XFS_QUOTA_UDQ_ENFD (for user quota), or XFS_QUOTA_GDQ_ACCT and/or XFS_QUOTA_GDQ_ENFD (for group quota), as defined in <xfs/xqm.h>. This call is restricted to the superuser.
Turn off quotas for an XFS filesystem. As in 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. This call is restricted to the superuser.
Get disk quota limits and current usage for user id. addr is a pointer to a fs_disk_quota structure (defined in <xfs/xqm.h>). Only the superuser may get the quotas of a user other than himself.
Set disk quota limits for user id. addr is a pointer to afs_disk_quota structure (defined in <xfs/xqm.h>). This call is restricted to the superuser.
Returns a fs_quota_stat structure containing XFS filesystem specific quota information. This is useful in finding out how much space is spent to store quota information, and also to get quotaon/off status of a given local XFS filesystem.
Free the disk space taken by disk quotas. Quotas must have already been turned off.
There is no command equivalent to Q_SYNC for XFS since sync(1) writes quota information to disk (in addition to the other filesystem metadata it writes out).
on failure and sets errno to indicate the error.
addr or special are invalid.
The kernel has not been compiled with the QUOTA option.
cmd or type is invalid.
The file specified by special or addr does not exist.
special is not a block device.
The call is privileged and the caller was not the super-user.
No disc quota is found for the indicated user.
Quotas have not been turned on for this filesystem.
If cmd is Q_QUOTAON, quotactl() may set errno to:
The quota file pointed to by addr exists but is not a regular file.
The quota file pointed to by addr exists but is not on the filesystem pointed to by special.
The quota file is corrupted.
Specified quota format was not found.
Q_QUOTAON attempted while another Q_QUOTAON has already taken place.