CHOWN Examples

2016

CHOWN is the Linux CHange OWNer Command. This allows the owner of a file or directory to be changed between users.

Change the owner of a file

  # ls -lart tmpfile    [ls is used to diplay the file/directory properties]
  -rw-r--r-- 1 himanshu family 0 2012-05-22 20:03 tmpfile
  
  # chown root tmpfile
  
  # ls -l tmpfile
  -rw-r--r-- 1 root family 0 2012-05-22 20:03 tmpfile

Change the group of a file

  Through the chown command, the group (that a file belongs to) can also be changed.
  # ls -l tmpfile
  -rw-r--r-- 1 himanshu family 0 2012-05-22 20:03 tmpfile
  
  # chown :friends tmpfile
  
  # ls -l tmpfile
  -rw-r--r-- 1 himanshu friends 0 2012-05-22 20:03 tmpfile

Change both owner and the group

  # ls -l tmpfile
  -rw-r--r-- 1 root family 0 2012-05-22 20:03 tmpfile
  
  # chown himanshu:friends tmpfile
  
  # ls -l tmpfile
  -rw-r--r-- 1 himanshu friends 0 2012-05-22 20:03 tmpfile

Change owner only if a file is owned by a particular user

Using chown “–from” flag, you can change the owner of a file, only if that file is already owned by a particular owner.

  # ls -l tmpfile
  -rw-r--r-- 1 root friends 0 2012-05-22 20:03 tmpfile
  
  # chown --from=guest himanshu tmpfile
  
  # ls -l tmpfile
  -rw-r--r-- 1 root friends 0 2012-05-22 20:03 tmpfile
  
  # chown --from=root himanshu tmpfile
  
  # ls -l tmpfile
  -rw-r--r-- 1 himanshu friends 0 2012-05-22 20:03 tmpfile

In the example above, we verified that the original owner/group of the file ‘tmpfile’ was root/friends.
Next we used the ‘–from’ flag to change the owner to ‘himanshu’ but only if the existing owner is ‘guest’.
Now, as the existing owner was not ‘guest’. So, the command failed to change the owner of the file.
Next we tried to change the owner if the existing owner is ‘root’ (which was true) and this time command was successful and the owner was changed to ‘himanshu’.

Copy the owner/group settings from one file to another

  This is possible by using the ‘–reference’ flag.
  
  # ls -l file
  -rwxr-xr-x 1 himanshu family 8968 2012-04-09 07:10 file
  
  # ls -l tmpfile
  -rw-r--r-- 1 root friends 0 2012-05-22 20:03 tmpfile
  
  # chown --reference=file tmpfile
  
  # ls -l tmpfile
  -rw-r--r-- 1 himanshu family 0 2012-05-22 20:03 tmpfile

In the above example, we first checked the owner/group of the reference-file ‘file’ and then checked the owner/group of the target-file ‘tmpfile’. Both were different. Then we used the chown command with the ‘–reference’ option to apply the owner/group settings from the reference file to the target file. The command was successful and the owner/group settings of ‘tmpfile’ were made similar to the ‘file’

List all the changes made by the chown command

  Use the verbose option -v, which will display whether the ownership of the file was changed 
  or retained as shown below.
  
  # chown -v -R guest:friends linux
  changed ownership of `linux/redhat/rh7' to guest:friends
  changed ownership of `linux/redhat' retained to guest:friends
  ownership of `linux/redhat_sym' retained as guest:friends
  ownership of `linux/ubuntu_sym' retained as guest:friends
  changed ownership of `linux/linuxKernel' to guest:friends
  changed ownership of `linux/ubuntu/ub10' to guest:friends
  ownership of `linux/ubuntu' retained as guest:friends
  ownership of `linux' retained as guest:friends

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