Introduction to Linux common hard disk management commands

1. df command

The df command is used to count the usage of partitions.

[root@localhost ~]# df -ahT

Options:

-a : Display special file systems, which are almost all stored in memory. For example, proc is mounted in memory, so the usage is 0.

-h : Convert to units that humans are accustomed to seeing (human-friendly display).

-T : Add an extra column for file system types.

Here is an example:

[root@localhost ~]# df -hT 
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda3 ext4 19G 2.2G 16G 13% /
tmpfs tmpfs 495M 0 495M 0% /dev/shm
/dev/sdal ext4 190M 33M 147M 19% /boot

Result description:

Filesystem : Device file name.

Type : File system type.

Size : The total size of the partition.

Used : Occupied size.

Avail : How much free time is available.

Use% : Utilization rate.

Mounted on : Mount point.

2. du command

The du command is used to count the size of directories or files.

[root@localhost ~]# du [options] [directory or file name]

Options:

-a : Display the disk usage of each subfile. By default, only the disk usage of subdirectories is counted.

-h : Display disk usage in customary units, such as KB, MB, or GB (human-friendly display).

-s : Count the total usage without listing the usage of subdirectories and subfiles.

(1) The directory size statistics of ls or ll command are inaccurate. Why?

We use ls or ll command to check the file size. The directory size is usually 0K or 4k or a multiple of 4K .

As shown below: Except for the boot directory and dev directory.

After I decompressed a 6.2M compressed package, the resulting folder also showed 4K .

As shown in the following figure:

The file obtained after decompression is much smaller than the compressed file, which is obviously incorrect data.

This is obviously an unreasonable situation.

This indicates that there is a problem with the file size statistics of ls or ll command, and the directory size statistics data is inaccurate.

The reason for this problem has to do with partitioning.

A directory has its own block , block stores the file name and the corresponding i node number, as well as the file name and i node number data of the files in the directory. The directory block does not count the size of the files in the directory.

The data that records the file name and corresponding i -node number of the directory, and the file name and i node number of the file in the directory, if it can be contained in one block , it is 4K . If it cannot be contained, it is stored in multiple block , which is a multiple of 4K .

So execute the [root@localhost ~]# du -h httpd-2.2.9 command to see the size of each file in httpd-2.2.9 directory, and finally the size of the httpd-2.2.9 directory will be displayed.

If you only need to see the total size of the files, add option s .

[root@localhost ~]# du -hs httpd-2.2.9

explain:

Why is the boot directory 1K in size? Because we mentioned before that the block size is 1K, 2K, or 4K (default), but boot is a separate partition and the default size is 1KB.

The dev directory is a special hardware directory, which contains information about devices such as hard disks. It is quite special, so it is excluded.

(2) The difference between du command and df command

The du command is used to count the file size, and the counted file size is accurate.

The df command is used to count the size of the space (both files and temporary files are counted, and the space will be released after restart). The usage rate of the partition is accurate (to be more specific, the remaining space of the partition is accurate).

In addition, if you cannot restart the server at work and want to free up the space occupied by temporary files, you can also release it manually.

sof I grep deleted : is a command to query the hidden status of files, find out the files to be deleted, and then manually kill one process at a time.

This method is extremely difficult to operate and the chance of error is high. Manual release is not recommended.

The loss caused by a planned restart of a Linux server is much smaller than the loss caused by an unexpected server downtime or restart.

3. fsck file system repair command

This command is a file system repair command that comes with the Linux system.

This command is a bit like the Windows system not shutting down normally (sudden power outage), and the next time you start the computer, you will be prompted whether to scan and repair files.

Automatic repair commands:

[root@localhost ~]# fsck -y /dev/sdb1

This command will be automatically executed when the Linux system is started. If the file can be repaired through the fsck command, it will be repaired automatically when the computer is turned on. If the file still reports an error after the Linux system is started, manually executing the fsck command will be useless and the repair will not be successful.

4. Display disk status dumpe2fs

To display the disk status, use the dumpe2fs command and execute dumpe2fs + 分區號to view it.

How to query the partition number? It is very convenient to query it through the df -h command.

Here are the results of executing the command:

There is a lot of information above. If you only want to see the super block information (that is, the top part of the information), just add the -h option.

as follows:

[root@localhost ~]# dumpe2fs -h /dev/sda3

5. View the detailed time of the file

stat 文件名: view the detailed time of the file.

The results of executing the command are as follows:

It's okay as long as you can understand this information. Just understand it.

6. Determine the file type

file 文件名: determine the file type

type 命令名: determine the command type

Determine the file type

If we judge a file, it will show that the file is an English document in ASCII code.

[root@localhost ~]# file anaconda-ks.cfg
anaconda-ks.cfg: ASCII English text

If we judge a directory, it will show that the file is a directory.

[root@localhost ~]# file 123/
123/: directory

Determine the command type

The commands in the Linux system are divided into internal commands and external commands

If you use the type command to determine the command type, if there is a command location, it means it is an external command.

as follows:

[root@localhost ~]# type mkdir
mkdir is /bin/mkdir

If you use the type command to determine the command type and it displays shell builtin (shell built-in command), it means it is an internal command.

as follows:

[root@localhost ~]# type cd
cd is a shell builtin

If a command has an alias, use the type command to determine the command type, and the command alias information will be displayed.

[root@localhost ~]# type ls
ls is aliased to 'ls --color=auto'

Tip: These two commands are generally used when writing script programs. It is very convenient for us to distinguish between files and folders (using our eyes, haha).

This is the end of this article about the commonly used Linux hard disk management commands. For more relevant Linux hard disk management command content, please search 123WORDPRESS.COM’s previous articles or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!