How to use the command chown (with examples)

The ‘chown’ command is used to change the user and group ownership of files and directories in Linux. It provides a way to modify the ownership information of a file or directory, allowing users to control who can access and make changes to their files. The ownership information consists of a user and group.

Use case 1: Change the owner user of a file/directory

Code:

chown user path/to/file_or_directory

Motivation: Sometimes, it becomes necessary to change the owner user of a file or directory. This is useful when, for example, a user wants to transfer their files to another user account or give ownership of specific files to someone else.

Explanation: In this use case, ‘user’ is the new owner of the file or directory specified by ‘path/to/file_or_directory’. The ‘user’ can be specified either by the username or the numeric user ID (UID).

Example output:

$ ls -l file.txt
-rw-r--r-- 1 olduser olduser 0 Oct 1 11:00 file.txt

$ chown newuser file.txt

$ ls -l file.txt
-rw-r--r-- 1 newuser olduser 0 Oct 1 11:00 file.txt

Use case 2: Change the owner user and group of a file/directory

Code:

chown user:group path/to/file_or_directory

Motivation: Similar to the previous use case, sometimes it is necessary to change both the owner user and group of a file or directory. This can be useful when files need to be managed by multiple users or groups.

Explanation: In this use case, ‘user’ is the new owner user and ‘group’ is the new group of the file or directory specified by ‘path/to/file_or_directory’. Both ‘user’ and ‘group’ can be specified either by their names or their numeric IDs.

Example output:

$ ls -l file.txt
-rw-r--r-- 1 olduser oldgroup 0 Oct 1 11:00 file.txt

$ chown newuser:newgroup file.txt

$ ls -l file.txt
-rw-r--r-- 1 newuser newgroup 0 Oct 1 11:00 file.txt

Use case 3: Recursively change the owner of a directory and its contents

Code:

chown -R user path/to/directory

Motivation: Occasionally, there is a need to change the owner of a directory and all its files and subdirectories. This is particularly useful when transferring ownership of an entire directory structure or when correcting improper ownership settings.

Explanation: In this use case, the ‘-R’ option is used to recursively change the owner of the directory specified by ‘path/to/directory’ and all its contents.

Example output:

$ ls -l directory
drwxr-xr-x 1 olduser olduser 0 Oct 1 11:00 subdirectory
-rw-r--r-- 1 olduser olduser 0 Oct 1 11:00 file.txt

$ chown -R newuser directory

$ ls -l directory
drwxr-xr-x 1 newuser newuser 0 Oct 1 11:00 subdirectory
-rw-r--r-- 1 newuser newuser 0 Oct 1 11:00 file.txt

Use case 4: Change the owner of a symbolic link

Code:

chown -h user path/to/symlink

Motivation: Sometimes, there is a need to change the owner of a symbolic link. This can be useful when transferring ownership of resources that are linked.

Explanation: In this use case, the ‘-h’ option is used to change the ownership of the symbolic link specified by ‘path/to/symlink’, rather than the file it points to.

Example output:

$ ls -l symlink.txt
lrwxrwxrwx 1 olduser olduser 8 Oct 1 11:00 symlink.txt -> file.txt

$ chown -h newuser symlink.txt

$ ls -l symlink.txt
lrwxrwxrwx 1 newuser olduser 8 Oct 1 11:00 symlink.txt -> file.txt

Use case 5: Change the owner of a file/directory to match a reference file

Code:

chown --reference=path/to/reference_file path/to/file_or_directory

Motivation: Occasionally, there is a need to set the ownership of a file or directory to match that of a reference file. This can be useful when ensuring consistent ownership settings between related files and directories.

Explanation: In this use case, ‘–reference=path/to/reference_file’ specifies the reference file from which the ownership is obtained. The ownership of the file or directory specified by ‘path/to/file_or_directory’ will then be set to match the ownership information of the reference file.

Example output:

$ ls -l reference_file
-rw-r--r-- 1 refuser refgroup 0 Oct 1 11:00 reference_file
$ ls -l file.txt
-rw-r--r-- 1 olduser oldgroup 0 Oct 1 11:00 file.txt

$ chown --reference=reference_file file.txt

$ ls -l file.txt
-rw-r--r-- 1 refuser refgroup 0 Oct 1 11:00 file.txt

Conclusion:

The ‘chown’ command provides a flexible way to change the user and group ownership of files and directories in Linux. With its various options, it allows users to easily modify ownership settings to ensure proper access and control over their files.