How to check disk and directory status information under Linux

Today I will introduce to you the usage of two commands in the Linux system-df and du. The df command can view the disk usage information of the file system, and du can be used to view the size of the file or directory.

df

Usage: df [options]

Common options:

• -a Show all File system

• -h Display in an easy-to-read manner

• -i Disk capacity is not displayed, only the number of inodes used

• -T Display file system

Let’s do a demonstration

1. Without any parameters

# df
Filesystem     1K-blocks     Used Available Use% Mounted on
devtmpfs         3986648        0   3986648   0% /dev
tmpfs            3999984        0   3999984   0% /dev/shm
tmpfs            3999984      528   3999456   1% /run
tmpfs            3999984        0   3999984   0% /sys/fs/cgroup
/dev/vda1       41931756 19293976  22637780  47% /
/dev/vdb1       52403200   476572  51926628   1% /data
/dev/vdb2      104806400 27960008  76846392  27% /www
tmpfs             799996        0    799996   0% /run/user/0

2 .Add the -h option

to get the disk usage of each mount point, but it is not very easy to read. Let's add the -h option to see the effect

# df -h
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        3.9G     0  3.9G   0% /dev
tmpfs           3.9G     0  3.9G   0% /dev/shm
tmpfs           3.9G  528K  3.9G   1% /run
tmpfs           3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/vda1        40G   19G   22G  47% /
/dev/vdb1        50G  466M   50G   1% /data
/dev/vdb2       100G   27G   74G  27% /www
tmpfs           782M     0  782M   0% /run/user/0

3. Add the -T option

We also want to know what kind of file system the mount point uses, so we need to add Use the -T option

# df -hT
Filesystem     Type      Size  Used Avail Use% Mounted on
devtmpfs       devtmpfs  3.9G     0  3.9G   0% /dev
tmpfs          tmpfs     3.9G     0  3.9G   0% /dev/shm
tmpfs          tmpfs     3.9G  528K  3.9G   1% /run
tmpfs          tmpfs     3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/vda1      xfs        40G   19G   22G  47% /
/dev/vdb1      xfs        50G  466M   50G   1% /data
/dev/vdb2      xfs       100G   27G   74G  27% /www
tmpfs          tmpfs     782M     0  782M   0% /run/user/0

4. Add the -i option

If we want to see the inode usage, then we need to use the -i option

# df -ih
Filesystem     Inodes IUsed IFree IUse% Mounted on
devtmpfs         974K   359  973K    1% /dev
tmpfs            977K     1  977K    1% /dev/shm
tmpfs            977K   562  977K    1% /run
tmpfs            977K    17  977K    1% /sys/fs/cgroup
/dev/vda1         20M  188K   20M    1% /
/dev/vdb1         25M     4   25M    1% /data
/dev/vdb2         50M  494K   50M    1% /www
tmpfs            977K     5  977K    1% /run/user/0

Except In addition to the above options, df also has a very useful little function, which can check which file system a file belongs to.

# df /etc/my.cnf
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/vda1       41931756 19294292  22637464  47% /

du

Like df, du is also a frequently used command. Sometimes, the server disk is almost full and we need to clean up unnecessary large files. At this time, we need the du command.

Usage: du [option] file or directory name

Commonly used options are as follows:

• -a Display the size of all files

• -h Display in human-readable form.

• -s Display only the total

• -S Display the directory size, but does not include the size of the subdirectory

# 显示文件大小
# du -h wp-fastest-cache.0.9.0.7.zip 
456K wp-fastest-cache.0.9.0.7.zip

# 显示目录大小，默认会显示该目录下所有文件，如只想显示目录大小，需要加上-s选项
# du -sh /root
114M /root

# 显示目录下文件大小总和，不包括子目录
# du -sSh /root
84M /root

Below, a very common scenario is given: the system disk is almost full and needs to be cleaned up.

First, we use the df command to check which file system is almost running out of space. After locating the mount point, use the du command to go through the directories one by one to check the directory size and locate the directory that takes up the largest space. Then look at the files that can be deleted in this directory and delete these files.

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