Disk quota management: Some concepts

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## 1. Some concepts

## 1.1 Per device/partition control

Disk quotas are managed partition by partition. There is no relation between the disk quotas setup for each partition. Further, you may enable disk quotas on some partitions while disabling them on others.

## 1.2 User and group quotas

You can control disk quota user per user. You can also work at the group level. Both quotas are setup completely independently. A group with a hundred users may have a disk space quota of much less than the sum of the users' quotas.

When a file is created by a user, it belong to that user and to some group. The disk quota records of both the user and group are updated.

A user may have plenty of available disk quota, but the group may be out of quota. Because of that the user won't be able to use more disk space while active in that group. This will not prevent them from doing work in another group assuming that the space is available, though they will need to switch to that group before this can occur.

## 1.3 Group quotas and Members default quotas

Linuxconf lets you manage quota with great flexibility. While you can can configure the quota limits user per user, most administrators will choose to operate more globally. Further, Linuxconf lets you partially fill quota specifications. This lets you use some defaults for a user and override only a single specification (maximum files allowed for example).

## 1.4 Disk quota information

You can control two aspects with disk quotas, (1) the number of files and directories owned by a user (or group) and (2) the amount of disk space owned. Both options are controlled separately. It is possible to have no limit on one while enforcing some limits on the other.

Each aspect is controlled by three parameters:

- Soft limit The soft limit is a proposed operational limit. The user/group may exceed this limit, but only for a limited amount of time.
- Hard limit This limit can't be exceed.
- Grace period This is the length of time the user/group may exceed the soft limit. It defaults to 7 days, and is expressed in a days:hours:minutes:seconds format.

## 1.5 Possible values for a limit

A given limit may have three values:

- 0 This means no limits
- -1 This means unspecified. The effective value is inherited from the defaults.
- Some value greater than 0 This is a limit. For disk space, this is expressed in kilobytes, and is true whatever the block size used on the disk. Linuxconf will translate the kilobytes to fit the disk subsystem requirements.

## 1.6 Effective quotas for users

Disk quotas for a user are influenced by three setups:

- The user records Those records are visible in the user account dialog. There is one record per partition with user quotas enabled.
- The defaults for group members Don't confuse this with group quotas. You can set up default values for disk quotas which apply directly to the members of the group. You modify these defaults right in the group account dialog. There is one record per partition with user quotas enabled.
- General default values One record per partition provides the base defaults. Often this will be the only record modified with all users inheriting these values.

## 1.7 Effective quotas for groups

Disk quotas for a group are influenced by two setups:

- The group records These records are visible in the group account dialog. There is one record per partition with group quota enabled.
- General default values One record per partition provides the base defaults. Often this will be the only record modified with all groups inheriting these values.

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