38

How do you use the cp command without changing the target file's permissions? For example:

cp /tmp/file   /home/file

I don't want to change chown and chgrp on /home/file.

4
  • 3
    It's not clear whether you are asking about preserving the source permissions or the target permissions. You've also cross-site spammed to SuperUser.
    – Tom Shaw
    May 26, 2011 at 9:00
  • For the record, the "preservation" options are in reference to the source. cp -p makes the target attributes match (thereby preserving) the source attributes.
    – mpersico
    Apr 20, 2017 at 16:54
  • 3
    I just stumbled upon this page. cp by default ought to preserve the target files permissions and user:group because it opens the target in update mode and retaining its inode. So it's not clear to my why the answers don't indicate this.
    – dozer
    Apr 21, 2017 at 11:58
  • 1
    This question is moot. GNU cp default behaviour is as desired by this question, as demonstrated here.
    – Tom Hale
    Jan 3, 2021 at 9:59

6 Answers 6

41

If you've only opened the manual for cp...

The next will not overwrite the file permissions and ownership + groupship:

cp --no-preserve=mode,ownership /tmp/file /home/file

Note that root privileges are needed if you want to preserve the ownership and groupship.

An excerpt from the manual:

  --preserve[=ATTR_LIST]
      preserve   the   specified   attributes   (default:  mode,owner-
      ship,timestamps), if possible  additional  attributes:  context,
      links, xattr, all
4
  • 3
    Not exactly what the author wanted. --no-preserve makes sense if used after --preserve (or its aliases), otherwise it doesn't affect the behavior of cp. The author wanted to keep the file mode of an existing target file and only overwrite its contents
    – basin
    Oct 2, 2018 at 9:15
  • 1
    Ex: replace ssh host keys cp --no-preserve=mode,ownership ssh* /etc/ssh/. This makes the secret keys world-readable.
    – basin
    Oct 2, 2018 at 9:20
  • 1
    The man page's --preserve explanation is IMHO nonsensical as it does not make it clear preserve what: The source or target attributes
    – Waslap
    Feb 22, 2019 at 12:40
  • --no-preserve=all is default. And by default GNU cp doesn't update target permissions anyway.
    – Tom Hale
    Jan 3, 2021 at 10:05
13

cat will work, too:

cat /tmp/file > /home/file
3
  • 1
    does it work for binary files too ?
    – beppe9000
    Jan 23, 2020 at 15:16
  • @beppe9000 yes, cat outputs whatever it inputs.
    – Tom Hale
    Jan 3, 2021 at 9:33
  • For an answer that works with sudo, see here
    – Tom Hale
    Jan 3, 2021 at 9:43
4

By default, GNU cp (version 8.32) will NOT overwrite destination permissions, so the question is moot:

% ls -li
total 8,192
19392015 -rwxrwxrwx 1 ravi ravi 4 Jan  3 16:54 bar*
19392014 -rw-r--r-- 1 ravi ravi 4 Jan  3 16:46 foo
% cp foo bar
% ls -li
total 8,192
19392015 -rwxrwxrwx 1 ravi ravi 4 Jan  3 16:57 bar*
19392014 -rw-r--r-- 1 ravi ravi 4 Jan  3 16:46 foo
%

In the case where the destination file is not writable (even though the directory is), cp will say:

cp: cannot create regular file 'dest-file': Permission denied

Other options besides cp:

cat will preserve the inode and permissions of the destination file:

cat file-with-new-data > file-to-overwrite

However, redirections won't work with sudo.

If you want to sudo and keep the destination permissions, use this:

< file-with-new-data sudo tee file-to-overwrite > /dev/null

This is equivalent to the more verbose:

cat file-with-new-data | sudo tee file-to-overwrite > /dev/null
1
  • I verified cp version 8.26 also keeps the permissions/owner/group of the file being overwritten. May 19, 2021 at 15:16
-1

Or you can use even better install program from GNU coreutils that has been made for this particular purpose. Please note it is not able to recurse (no -R or -r option).

http://www.gnu.org/software/coreutils/manual/html_node/install-invocation.html

1
  • 1
    I didn't see a switch for this to preserve the target's ower or group. Just force it to a new value.
    – Pete
    Oct 7, 2015 at 22:06
-1

Don't use permission-related switches at all, especially --no-preserve, because it behaves strangely:

good:

[il@localhost Downloads]$ sudo cp ssh_host_* /etc/ssh/
[il@localhost Downloads]$ ls -l /etc/ssh
total 604
-rw-r--r--  1 root root     581843 Oct 20  2017 moduli
-rw-r--r--  1 root root       2276 Oct 20  2017 ssh_config
-rw-------  1 root root       3907 Oct 20  2017 sshd_config
-rw-r-----. 1 root ssh_keys    227 Oct  2 12:26 ssh_host_ecdsa_key
-rw-r--r--. 1 root root        172 Oct  2 12:26 ssh_host_ecdsa_key.pub
-rw-r-----. 1 root ssh_keys    411 Oct  2 12:26 ssh_host_ed25519_key
-rw-r--r--. 1 root root        100 Oct  2 12:26 ssh_host_ed25519_key.pub
-rw-r-----. 1 root ssh_keys   1679 Oct  2 12:26 ssh_host_rsa_key
-rw-r--r--. 1 root root        392 Oct  2 12:26 ssh_host_rsa_key.pub

bad:

[il@localhost Downloads]$ sudo cp --no-preserve=mode,ownership ssh_host_* /etc/ssh/
[il@localhost Downloads]$ ls -l /etc/ssh
total 604
-rw-r--r--  1 root root     581843 Oct 20  2017 moduli
-rw-r--r--  1 root root       2276 Oct 20  2017 ssh_config
-rw-------  1 root root       3907 Oct 20  2017 sshd_config
-rw-r--r--. 1 root ssh_keys    227 Oct  2 12:27 ssh_host_ecdsa_key
-rw-r--r--. 1 root root        172 Oct  2 12:27 ssh_host_ecdsa_key.pub
-rw-r--r--. 1 root ssh_keys    411 Oct  2 12:27 ssh_host_ed25519_key
-rw-r--r--. 1 root root        100 Oct  2 12:27 ssh_host_ed25519_key.pub
-rw-r--r--. 1 root ssh_keys   1679 Oct  2 12:27 ssh_host_rsa_key
-rw-r--r--. 1 root root        392 Oct  2 12:27 ssh_host_rsa_key.pub
-2

The cp doesn't override permissions by default. If you want to make sure permission won't be overridden, use

cp --preserve=mode,ownership /tmp/file /target_dir_where_file_resides
1
  • 2
    That actually forces overwriting of the target permissions -- it preserves the permissions of the source file.
    – Tom Hale
    Jan 3, 2021 at 9:44

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