chown Command in Linux: Changing Owner and Group of Files

The chown command in Linux changes the file owner and can also change the group the file belongs to.

In most permission problems, novice Linux users tend to change file permissions with the chmod command. But usually, changing the ownership of the parent directory or a file is sufficient. So pay attention to this post.

The chown command allows the following options:

• -v: Reports the owner of the files, including ownership changes;
• -c: Reports only the ownership change;
• -R: Changes the owner of all files and directories recursively within the same hierarchy.

The chown command can receive as a parameter:

Login
If only the user's login is provided, the file Owner property changes, but the group property remains unchanged.
Login:group
If a "login:group" or "login.group" is provided, both the file owner and the group are changed.
Login:
If a "login:"  or "login." is provided without specifying the group, the file owner is changed, and the group is changed to the group the specified login belongs to.
:group
If ":group" or ".group" is provided without specifying the login, chown will act like the chgrp command, changing only the file's group.

Examples:

Changes the owner of the file Readme.txt to user uira:

$ chown uira Leiame.txt

Changes the owner of the file Readme.txt to user uira and the file's group to the user's group:

$ chown uira. Leiame.txt

Changes the owner of the file Readme.txt to user uira and the group to users:

$ chown uira:users Leiame.txt

Changes the file's group to users and leaves the file's owner unchanged:

$ chown .users Leiame.txt

Changes the owner of all files and directories within /home/uira to user uira:

$ chown –R uira /home/uira

A regular user can only transfer ownership of files and directories they own. The root user can change the ownership of any file or directory.

Most of the time, it is not necessary to change a directory's permissions to "777" as a way to grant permissions for a program to access it. Just check with the "ps -aux" command which user is running the program, and change the owner of the directory or file, or the group.

See PHP for example:

$ ps aux | grep phpapache    1232  0.1  2.6 533340 208332 ?       S    mai25   3:12 php-fpm: pool wwwapache    1233  0.1  2.6 773088 205856 ?       Sl   mai25   3:57 php-fpm: pool www

In this example, the user running php-fpm is apache.

So, to give permission for php to write something to the upload directory, it is not necessary to change the permission, but rather the directory's owner:

$ ls -l |grep uploaddrwxr-xr-x  2 root   root        4096 mai  25 22:33 upload

You then change the owner of the upload directory to user apache. This way, the php-fpm process will be able to write, read, and access the upload directory:

$ sudo chown apache upload$ ls -l |grep uploaddrwxr-xr-x  2 apache   root        4096 mai  25 22:33 upload

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