Centos – Permission changes after extracting tgz file

centoscompressiontar

While extracting a tgz file, I have noticed that the permission changes to something weird! The tgz file belongs to root:root however, the folder belongs to 502:games

[root@rocks7 common]# ls -l
-rw-r--r-- 1 root root 4779534 May  2  2012 scalapack-2.0.2.tgz
[root@rocks7 common]# tar xf scalapack-2.0.2.tgz
[root@rocks7 common]# 
[root@rocks7 common]# ls -l
total 98576
drwxr-xr-x 10  502 games     4096 May  2  2012 scalapack-2.0.2
-rw-r--r--  1 root root   4779534 May  2  2012 scalapack-2.0.2.tgz

What is the issue here?

Best Answer

The tarball contains a scalapack-2.0.2 directory owned by user id 502 and whatever group id corresponds to the games group (or, perhaps, the games group by name). You can see this by running

tar tvf scalapack-2.0.2.tgz

Tar archives store ownership and permissions in addition to the file contents; since you’re extracting as root, that metadata is applied to the extracted files. The ownership of the tarball itself has no impact on the ownership of the extracted data.

Since you’re running CentOS, you’re presumably running GNU tar, and you can use the --no-same-owner and --no-same-permissions options to extract tarballs without applying the stored ownership and permissions. Other tar implementations may have similar options (e.g. -o on FreeBSD tar).

Related Solutions

Copy just permissions and ownership from one tar file to another

I'm not sure Tar can do that. It should be possible, though, to untar both backups (to different directories), then use something along the lines of

cd /mnt/oldbackup ; 
find ./ -exec getfacl {} | setfacl /mnt/newbackup/{}

as the output of getfacl can be used as stdin for setfacl according to the manpage.

CentOS – How to Have Files Extracted from Archive Inherit Permission from Parent Folder

I'm still looking for a better solution, but for now I created a a script that pipe tar output to chmod command

#!/bin/bash -
set -o pipefail
tar xvf "$@" | xargs -rd '\n' chmod 770 --

I don't like it so much because instruct 100 and more user to use a different command will be tricky but if won't find better solution I'll keep this. just for info from man page tar seems to have an option which should ignore the file permission

--no-same-permissions

but seems working only if umask permission are more restrictive than the one on the extracted files, wonder if it's a bug

Best Answer

Related Solutions

Copy just permissions and ownership from one tar file to another

CentOS – How to Have Files Extracted from Archive Inherit Permission from Parent Folder

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