Overview
This article shows how to change file or directory permissions using SSH or FTP. See this article for an overview of how permissions are configured.
Changing permissions via SSH
If you're logged into your server via SSH, you can change permissions by running the chmod command. There are two ways to set permissions using chmod.
Option 1 — Numeric Mode
Numeric Mode is easier to understand as you just need to add up the values to assign numbers to each permission. For example:
- 4 = r (read)
- 2 = w (write)
- 1 = x (execute)
There are three sets of owners of a file or directory:
- User
- Group
- Public
All three have their own permissions. Thus, all three must now be added together to get the full value. The following table illustrates the different permissions each owner could possibly have.
| 7 | read, write, and execute ("rwx") | 4 + 2 + 1 = 7 |
| 6 | read and write ("rw-") | 4 + 2 = 6 |
| 5 | read and execute ("r-x") | 4 + 0 + 1 = 5 |
| 4 | read only ("r--") | 4 + 0 + 0 = 4 |
| 3 | write and execute (rare) ("-wx") | 0 + 2 + 1 = 3 |
| 2 | write only (rare) ("-w-") | 0 + 2 + 0 = 2 |
| 1 | execute only (rare) ("--x") | 0 + 0 + 1 = 1 |
| 0 | no permissions ("---") | 0 + 0 + 0 = 0 |
Examples
| Command | Permissions |
|---|---|
[server]$ chmod 600 file.txt |
-rw-------
|
[server]$ chmod 700 dir |
drwx------
|
[server]$ chmod 755 file.txt |
-rwxr-xr-x
|
[server]$ chmod 644 file.txt |
-rw-r--r--
|
[server]$ chmod 664 file.txt |
-rw-rw-r--
|
Option 2 — Named Mode
There are two sets of permissions to assign when using 'Named Mode', which are who and what permissions. For example:
who permissions
| u | change the user bits |
| g | change the group bits |
| o | change the other bits |
| a | change the bits for everybody |
what permissions
| r | grant read access |
| w | grant write access |
| x | grant execute access |
| s | set the sticky bit |
Using ("+") and ("-") with the information above, you’d combine permissions from the who and what groups to assign the exact permissions you desire.
Format
The format to use chmod in the following commands is:
[server]$ chmod "groups"+"access" file.example
Examples
Allows everybody to read file.txt.
In the following example, a is the bit for 'everybody' and the r (read) permission is added:
[server]$ chmod a+r file.txt
Strips everybody of all permissions, except for the owner who retains any former permissions.
In the following example, g is group bit, o is the 'other users' bit and the - sign is removing all permissions (rwx):
[server]$ chmod go-rwx file.txt
The file named script.cgi is executable by the user and group.
In the following example, u is the user bit, g is the 'group' bit, and the x permission is added to both:
[server]$ chmod ug+x script.cgi
All files created in the directory somedir are owned by the group that owns somedir.
In the following example, g is the group bit and the s flag is added to it:
[server]$ chmod g+s somedir
Changing permissions in an FTP client
FTP clients such as Filezilla allow you to use the Numeric Mode to set permissions.
If you right-click on a file in an FTP client, you can view its permissions. For example:
You can then either check the boxes, or type in the Numeric value of the permissions you need to change.