Adjust file permissions with the Linux command chmod


Check permissions

Check the file permissions with the ls command.

$ ls -l

Meaning of permissions

Something like drwxr-xr-x represents the permission settings.

Alphabet meaning
d directory
r Read
w Writing
x Run
- Disallowed

The leading d indicates that it is a directory. The rest represents three patterns of permissions: owner, group user, and other users. drwxr-xr-x will be in the following state.

Owner (u) Group user (g) Other users (o)
d rwx r-x r-x
Directory Permission to read, write, and execute Read, execute permission, write disallow Read, execute permission, write disallow

Permission numbers

To express rwx as an octal number, it is as follows. 0 means no permission, 1 means permission.

rwx 8 base
000 0
001 1
010 2
011 3
100 4
101 5
110 6
111 7

If you want to allow the operation only to the owner rwx ------ becomes 111000000 and becomes 700.

How to use

Operate with plus and minus

Give the owner write permission to the specified file

$ chmod u+w test.txt

Remove the execute permission of the owner of the specified file

$ chmod u-x test.txt

Specify all by numbers

Or specify them all in octal numbers

$ chmod 700 test.txt

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