Common commands for Unix-like systems df and du detailed

DF Command verbose usage

A: Displays all file systems and disk usage scenarios for each partition
I: Show the usage of i-nodes
K: size is denoted by K (default value)
T: Displays all partition disk usage for one file system
X: Displays all partitions that are not part of a file system disk usage
T: Displays the name of the file system to which each partition belongs
Common commands: Df-hi

Detailed operation

Instruction DF can show the maximum available space and usage for all current file systems, see this example:

# df-h
Filesystem Size used Avail capacity mounted on
/DEV/AD0S1A 1.9G 389M 1.4G 21%/
Devfs 1.0K 1.0K 0B 100%/dev
/dev/ad0s1d 989M 54K 910M 0%/tmp
/dev/ad0s1f 4.8G 3.8G 657M 86%/usr
/dev/ad0s1e 1.9G 149M 1.6G 8%/var
/dev/ad0s1g 26G 890K 24G 0%/volume2
/dev/da0s1d 325G 261G 38G 87%/volume1

We added the parameter-H to use the "human-readable" output, that is, in the file system size using GB, MB and other easy-to-read format.

The first and last fields of the above instruction output are the file system and its hang-in points respectively. We can see that this partition of/DEV/AD0S1A is hung in the root directory. We mentioned in the previous section that ad represents the IDE's hard disk, and S1 represents the first major sector. I also have a SCSI hard disk, its code name is DA, it's large capacity, mainly used to store data. DEVFS is a special file system, which is not a real disk, but a virtual file system used by FreeBSD to manage the hardware of the system.

The next four fields size, used, Avail, and capacity are the partition's capacity, the size used, the remaining size, and the percentage used. When the hard disk is full, you may see that the percentage used is more than 100% because FreeBSD leaves some room for root, allowing Root to be managed by writing to the file system when the file system is full.

In addition, we can use the parameter-I to view the current use of the file system inode. Sometimes although the file system still has space, but if there is not enough inode to store the information of the file, the same will not add new files.

# Df-ih
Filesystem Size used Avail capacity iused ifree%iused mounted on
/DEV/AD0S1A 1.9G 389M 1.4G 21% 20495 262127 7%/
Devfs 1.0K 1.0K 0B 100% 0 0 100%/dev
/dev/ad0s1d 989M 62K 910M 0% 141286 0%/tmp
/dev/ad0s1f 4.8G 3.8G 657M 86% 311439 348015 47%/usr
/dev/ad0s1e 1.9G 149M 1.6G 8% 1758 280864 1%/var
/dev/ad0s1g 26G 890K 24G 0% 3532786 0%/volume2
/dev/da0s1d 325G 261G 38G 87% 707277 43311409 2%/volume1
We can see that the number of inode used in the root directory is 20495, and there are 262127 available inode.

Tips:
Remember what an inode is. The so-called Inode is the basic information (metadata) that is used to store files and directories, including time, file names, users, and groups. When splitting a sector, the system makes a bunch of inode for later use, and the number of inode is related to the total number of files and directories that can be created in the system. If most of the files to be saved are very small, then the same size of the hard disk will have more files, that is to say, more inode to hang files and directories.

du: Querying the disk usage space for an archive or directory

A: Displays the disk space occupied by all directories and each file under the second directory
B: Size is represented by bytes (default is k bytes)
C: Last plus Total (default value)
S: Show only the sum of each file size
X: Only files that belong to the same file system are counted
L: Calculate all file sizes
Common commands: Du-a

Detailed operation

Reference
The instruction du can display the amount of disk space occupied by all the files in each directory, in the subdirectories of the specified directory. For example:

# Du-h/etc
104k/etc/defaults
6.0k/etc/x11
8.0k/etc/bluetooth
4.0k/etc/gnats
52k/etc/isdn
388k/etc/mail
68k/etc/mtree
2.0k/etc/ntp
38k/etc/pam.d
44k/etc/periodic/daily
6.0k/etc/periodic/monthly
42k/etc/periodic/security
16k/etc/periodic/weekly
110k/etc/periodic
6.0k/etc/ppp
318k/etc/rc.d
2.0k/etc/skel
130k/etc/ssh
10k/etc/ssl
1.7m/etc
We use the-H parameter to display the format of the human-readable. In the application, we can use the DU command to see which directory occupies the most space. However, Du's output is usually very long, we can add the-s parameter to omit subdirectories under the specified directory, and only show the sum of that directory:

# DU-SH/ETC
1.7m/etc
When we look at the usage of the catalog, we can sort the output into the sorts directive to see which file uses the most space:

# Du/etc | Sort-nr | More
1746/etc
388/etc/mail
318/etc/rc.d
130/etc/ssh
110/etc/periodic
104/etc/defaults
68/etc/mtree
52/etc/isdn
44/etc/periodic/daily
42/etc/periodic/security
38/etc/pam.d
16/etc/periodic/weekly
10/etc/ssl
8/etc/bluetooth
6/etc/ppp
6/etc/periodic/monthly
6/etc/x11
4/etc/gnats
2/etc/skel
2/etc/ntp
The sort parameter,-nr, indicates that you want to reverse sort by the numeric sort, because we want to sort the size of the directory, so we can not use the size of the human-readable output, otherwise the directory size will have K, M and other words, will cause the sorting is incorrect.