What is linux disk quota

Disk quotas are used in Linux systems to limit the disk space or number of files occupied by specific ordinary users or user groups on specified partitions. They can be used to limit the web space, mail space and network available to each person. The amount of hard disk space. The users and user groups restricted by disk quotas can only be ordinary users and user groups; disk quota restrictions can only be targeted at partitions, not against a specific directory.

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

Disk quota (Quota) is used in Linux systems to limit the disk space or number of files occupied by specific ordinary users or user groups on a specified partition.

In this concept, there are the following key points to note:

• The users and user groups restricted by the disk quota can only be ordinary users and user groups, and also That is to say, the super user root cannot do disk quotas;

• Disk quota restrictions can only be for partitions, not for a certain directory. In other words, disk quotas can only be for file systems. Limit, for example, if your /dev/sda5 is mounted under /home, then all directories under /home will be subject to disk quota restrictions;

• We can limit the disk capacity (block) occupied by users, and of course we can also limit the number of files (inodes) allowed to be occupied by users.

Disk quotas are actually very common in real life. For example, no matter how big our mailbox is, it is limited, and it is impossible to store emails without limit; we can upload The file server also has capacity limits; it is impossible for us to use the personal space in the web page without restrictions.

Disk quota is like renting an office building. Although the space of the entire building is very large, the cost of renting the entire building is too high. We can rent it separately, and users can rent a larger space if they feel it is not enough. However, renting cannot be done casually. There are several rules that must be followed:

• My building is rented to outside users (ordinary users), but it can be rented to one person (user) , it can also be rented to a company (user group), but the ownership of this building is mine, so it cannot be rented to myself (root user);

• If you want to rent, then You can only rent a certain size of space on each floor, and cannot divide subspaces in a room for rent (quotas can only be for partitions, not for a certain directory);

• Tenants can decide how much space to rent on a certain floor (disk capacity limit), or how many personnel can be rented on a certain layer, so that only these few people can enter this layer (file number limit).

If disk quotas are to be used normally, there are several prerequisites:

1. The kernel must support disk quotas. Centos 6.x version of Linux supports disk quotas by default and does not require any modification. If you are concerned, you can check the kernel configuration file to see if disk quotas are supported. The command is as follows:

[root@localhost ~]# grep CONFIG_QUOTA /boot/corrfig-2.6.32-279.el6.i686
CONFIG_QUOTA=y
CONFIG_QUOTA_NETLINK_INTERFACE=y
# CONFIG_QUOTA_DEBUG is not set
CONFIG_QUOTA_TREE=y
CONFIG_QUOTACTL=y

You can see that the kernel already supports disk quotas. If the kernel does not support it, you need to recompile the kernel and add the quota supper function.

2. The Quota tool must be installed in the system. The Quoted tool is installed by default in our Linux. The check command is as follows:

[root@localhost ~]# rpm -qa | grep quota
quota-3.17-16.el6.i686

3. The disk quota function must be turned on for partitions that want to support disk quotas. This feature can be turned on manually and is no longer turned on by default.

Disk quotas can be used to limit the amount of web space, mail space, and network hard disk space available to each person. In addition, in terms of Linux system resource configuration, using disk quotas, you can also limit the maximum disk quota that can be used by a certain group or a certain user, and use Link to allow emails to be used as restricted quotas. (Change the path /var/spool/mail).

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