A quotas file (named
quotas) must exist in the root directory of a file system for any of the quota commands to work. For group quotas to work, there must be a
quotas.grp file. The files in the file system's mount point are referred to as the external quotas file. VxFS also maintains an internal quotas file for its own use.
The quota administration commands read and write to the external quotas file to obtain or change usage limits. VxFS uses the internal file to maintain counts of data blocks and inodes used by each user. When quotas are turned on, the quota limits are copied from the external quotas file into the internal quotas file. While quotas are on, all the changes in the usage information and changes to quotas are registered in the internal quotas file. When quotas are turned off, the contents of the internal quotas file are copied into the external quotas file so that all data between the two files is synchronized.
VxFS supports group quotas in addition to user quotas. Just as user quotas limit file system resource (disk blocks and the number of inodes) usage on individual users, group quotas specify and limit resource usage on a group basis. As with user quotas, group quotas provide a soft and hard limit for file system resources. If both user and group quotas are enabled, resource utilization is based on the most restrictive of the two limits for a given user.
To distinguish between group and user quotas, VxFS quota commands use a -g and -u option. The default is user quotas if neither option is specified. One exception to this rule is when you specify the -o quota option as a mount command option. In this case, both user and group quotas are enabled. Support for group quotas also requires a separate group quotas file. The VxFS group quota file is named
quotas.grp. The VxFS user quotas file is named
quotas. This name was used to distinguish it from the
quotas.user file used by other file systems under Linux.