What is the meaning of linux disk quota

Disk 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. It can be used to limit the web pages available to everyone. space, mail space, and network hard drive space. Only ordinary users and user groups can be restricted by disk quotas, and disk quota restrictions can only be applied to partitions and not to specific directories.

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 disk quota limit only applies to ordinary users and user groups. The super user root cannot set disks. Quota

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

• The user's disk space and number of files can be limited , for example, we can limit the number of disk blocks and inodes that a user can occupy.

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 entire building is very spacious, the cost of providing services to the entire building is too high. Users can rent each part separately, and if they need more space, they can rent it again. 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. Without any changes, Centos 6.x versions of Linux already support disk quotas by default. 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 have quota support, you need to recompile the kernel to add the quota supper function.

2. The Quota tool must be installed in the system. The following is the default installation and viewing command of the Quoted tool on our Linux

[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 limit the capacity of web space, mail space and network hard disk space that each person can use. 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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