Member Avatar for lewashby

I need to use the tar command to unpack a .tar.gz file and I need to do it from root but when the files unpack I want them to be owned by a specific user, not the root user. Can someone give me a hand?. I found the man pages confusing.

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Summary and quick options (short): run tar as the user who should own the files, or let root extract but have tar hand each file to a helper that writes it with the desired owner. Both avoid a separate recursive chown pass, but the simplest reliable fallback is still a post-extract chown (as suggested).

Extract as the target user
Run the extract under the identity that should own the files. That way the created files are owned correctly without further steps. This requires that the chosen user can write into the destination (or that sudo/runuser is used from a root script). The standard way to run a command as another user is to use sudo -u (or runuser/su). (sudo.ws)

One-pass extraction that sets owner during write
GNU tar can pipe each file to an external program with the --to-command option; the program sees environment variables such as TAR_FILENAME, TAR_SIZE and TAR_UID so it can write the file exactly where and how you want. Combining that with an installer program that supports setting owner (for example coreutils install with -o/-g) lets you write files owned by a specific user as they are extracted—useful when you must avoid a separate chown step. This is more advanced and typically requires a small wrapper to handle directories, modes and special files. (gnu.org)

Important tar behaviour and caveats
When run as root, tar will normally restore owners from the archive; you can tell tar not to try to restore stored ownerships with the no-same-owner option (but that makes files owned by the extracting user). Also: the --owner/--group override options are for archive creation (they do not force a different owner on extraction). If the archive contains numeric UIDs that do not match local names, mapping/remapping is needed or you will see numeric owners. (gnu.org)

Practical recommendation
If you control the destination and want a single simple command, extract as the target user (sudo -u or runuser). If you must run as root and want no second pass, use --to-command with a short script that uses install -o to write files with the requested owner (and handle dirs separately). Otherwise the reliable, low-complexity route is root extract + a single chown/chmod pass as noted by .

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Member Avatar for mike_2000_17

The easiest is probably to use chown to change the owner of the directory after you've extracted it. And you can use chmod too to remove some permissions for group and others too.

Let's say you have the file my_archive.tar.gz which contains a top-level directory called my_folder, and the user you want to make the owner of the folder is called "myself". Then, you can do this:

$ sudo su
# tar -xzf my_archive.tar.gz
# chown -R myself my_folder
# chmod -R go-w my_folder
# exit
$

This goes into superuser mode. Extracts the archive into the current directory (use cd to navigate to where you want to extract it first). Changes the ownership recursively (-R) to the user myself. Changes the access permissions recursively such that write access is removed from the "group" and "others", such that the read and execute permissions are preserved, and all permissions are preserved for the owner. Finally, it exits the superuser mode (you don't want to stay in that mode any longer than you need to).

Member Avatar for rubberman

You can use sudo to do this, as in "sudo userid tar -zxvf filename.tgz".

Member Avatar for davidnelson4911

If you have the permissions on the files set properly when they are put into the tar.gz archive then:

sudo tar -xpvzf filename.tar.gz

Will A: Ensure that it is run as root, B: Preserve the permissions of the files to the same as when compressed, and C: make like 100000x easier.

also, typically for linux you can do

somecommand --help

which will list all the available options for any 'somecommand' may seem overwhelming at first but I am sure you'll have it all figured out in no time.

on a sidenote. I use linux as my main computer 24/7, I have done so for over a year now. I dont remember 90% of the commands/options available on my machine at any given time, but I do remember some key tricks like tab complete, or double tabbing for all available commands,... etc. Most people dont remember off by heart every linux utility they use, and we don't expect you to either ;)

Member Avatar for rubberman

FWIW, when root untars a tar file, the files extracted should get the ownership and permissions of the original owner, as stored in the archive. If the original owner doesn't exists on the new system, or has a different UID, then it may appear that the files are owned by another user, or by a UID (User ID) that doesn't exist yet on the new system, such as 5001 instead of "Fred Flintstone".

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