Unix: Is there a way to "copy" file or directory permissions?

Question

I have two files in a directory. One has correct permissions and the other has not. Is there a way I can "copy" the set of permissions from one file to another?

Answer 1

The GNU version of the chmod utility can copy the mode from one file (RFile) to another (file).

chmod --reference=RFile file

GNU coreutils is found in most Linux distributions and Cygwin, among other places. Not all chmod implementations provide this option.

Answer 2

I came up with this:

find $SOURCE -mindepth 1 -printf 'chmod --reference=%p\t%p\n'|sed "s/\t$SOURCE/ $DEST/g"|sh

It is not fully bullet proof, but does what I need.

Answer 3

try this:

find /PATH/TO/TARGET -exec chmod --reference /PATH/TO/SOURCE/{} {} \;

this would go up recursivly and chmod every file, if two directory don't match on files you will see lots of "No such file or directory" error.

Answer 4

You can use getfacl to retrieve the full listing of file permissions, owner, group, and additional ACLs (access control lists).

$ getfacl filename.txt
# file: filename.txt
# owner: score
# group: score
user::rw-
group::---
other::---

If you save that output to a file (e.g. acl.txt), you can then restore from this format with setfacl --restore acl.txt. If you only want to restore a single file, and that file has a different filename to the original, you will want to use setfacl --set-file acl.txt filename.txt (where filename.txt is the new filename).

Steps

1. Save original permissions to acl.txt:

   $ getfacl filename.txt > acl.txt
   

2. Overwrite permissions (for demonstration; this is just so that you can see that restoring it in the next step works)

   $ chmod 777 filename.txt
   $ sudo chown nobody:root filename.txt
   $ ls -l filename.txt
   -rwxrwxrwx 1 nobody root 0 Jan  8 14:24 filename.txt
   

3. Use setfacl to restore correct permissions from acl.txt:

   $ sudo setfacl --restore acl.txt
   $ ls -l filename.txt
   -rw------- 1 score score 0 Jan  8 14:24 filename.txt
   

The filename is taken from the # file: comment generated by getfacl, so there is no need to specify it on the command line.

If you want to restore those permissions to a different file, you can use --set-file instead of --restore like so:

$ setfacl --set-file acl.txt second_filename.txt

Example

If you end up overwriting the permissions on some files in /usr, but you don't know what files you have overwritten, you can usually fix it by restoring from another similarly configured system.

1. Backup permissions from working system (note: getfacl generates relative paths, so ensure you cd to a consistent location on both machines)

   # cd /
   # getfacl -R usr > /root/acls.txt
   

2. Copy the ACL dump to the system with broken permissions

   $ scp root@working-system:/root/acls.txt .
   $ scp acls.txt root@broken-system:/root/
   

3. Restore the ACL dump to overwrite the broken permissions with those from the known good machine

   # cd /
   # setfacl --restore /root/acls.txt