df command

View the total capacity, used capacity, remaining capacity, etc. of the attached disk, without any parameters, which is displayed by K by default.

[root@centos-01 ~]# df
//file system          1K-block    Already used     Available used% Mount point
/dev/sda3      29140072 1040404 28099668    4% /
devtmpfs         490008       0   490008    0% /dev
tmpfs            499848       0   499848    0% /dev/shm
tmpfs            499848    6808   493040    2% /run
tmpfs            499848       0   499848    0% /sys/fs/cgroup
/dev/sda1        201380   99148   102232   50% /boot
tmpfs             99972       0    99972    0% /run/user/0

• "- h": display in appropriate units.

[root@centos-01 ~]# df -h
//File system capacity used available used% Mount point
/dev/sda3        28G 1016M   27G    4% /
devtmpfs        479M     0  479M    0% /dev
tmpfs           489M     0  489M    0% /dev/shm
tmpfs           489M  6.7M  482M    2% /run
tmpfs           489M     0  489M    0% /sys/fs/cgroup
/dev/sda1       197M   97M  100M   50% /boot
tmpfs            98M     0   98M    0% /run/user/0

The "/" and "/ boot" directories are shown here. Use the free command to view the swap

[root@centos-01 ~]# free
              total        used        free      shared  buff/cache   available
Mem:         999696      120460      731228        6808      148008      713160
Swap:       2097148           0     2097148

• "- i": View inodes usage

[root@centos-01 ~]# df -i
//file system          Inode Already used(I)  available(I) Already used(I)% Mount point
/dev/sda3      14577152   26523 14550629       1% /
devtmpfs         122502     372   122130       1% /dev
tmpfs            124962       1   124961       1% /dev/shm
tmpfs            124962     446   124516       1% /run
tmpfs            124962      16   124946       1% /sys/fs/cgroup
/dev/sda1        102400     327   102073       1% /boot
tmpfs            124962       1   124961       1% /run/user/0

• "- K" and "- M": displayed in K and M units respectively

[root@centos-01 ~]# df -m
//file system       1M-Block used available used% Mount point
/dev/sda3      28458  1016 27442    4% /
devtmpfs         479     0   479    0% /dev
tmpfs            489     0   489    0% /dev/shm
tmpfs            489     7   482    2% /run
tmpfs            489     0   489    0% /sys/fs/cgroup
/dev/sda1        197    97   100   50% /boot
tmpfs             98     0    98    0% /run/user/0

• Meaning of each column:

  The first column is the name of the partition, the second column is the total capacity of the partition, the third column is how much has been used, the fourth column is how much is left, the fifth column is the percentage used, and the sixth column (the last column) is the mount point.

”/dev/shm "is the memory mount point. If you want to put files in memory, you can put them in the directory / dev/shm /.

du command

• "- h": system automatic adjustment unit
• "- s": list only totals

[root@centos-01 ~]# du -sh /root/
40K /root/
[root@centos-01 ~]# du -sh /boot/
87M /boot/
[root@centos-01 ~]# du -sh /etc/passwd
4.0K    /etc/passwd
[root@centos-01 ~]# ls -lh /etc/passwd
-rw-r--r--. 1 root root 846 12month 27 05:28 /etc/passwd

ls shows the size of the file itself, du shows the amount of disk space occupied. The disk is divided into blocks. Each block is 4KB. Even if the file size is less than the size of one block, the file will occupy one block.

[root@centos-01 ~]# du /etc/passwd
4   /etc/passwd
[root@centos-01 ~]# du /root/
8   /root/.ssh
40  /root/

If du does not specify a unit, the default display unit is K.