sudo tar changes extracted files ownership to unknown user

Question

I am running this command:

$ sudo tar xvzf nexus-latest-bundle.tar.gz

The extracted files belong to an unknown (1001) user:

drwxr-xr-x 8     1001     1001      4096 Dec 16 18:37 nexus-2.12.0-01
drwxr-xr-x 3     1001     1001      4096 Dec 16 18:47 sonatype-work

Shouldn't it be root the owner under a normal configuration?

I am working on a linux installation replicated from an AWS AMI.

Solution 1

When extracting files as root, tar will use the original ownership. You can override that using the --no-same-owner option (alternatively, -o).

Your tar file referred to user/group which do not exist on the system where you extracted it.

If you extract files as yourself (a non-privileged user), you can only create files owned by yourself.

The GNU tar manual says:

--same-owner
When extracting an archive, tar will attempt to preserve the owner specified in the tar archive with this option present. This is the default behavior for the superuser; this option has an effect only for ordinary users. See section Handling File Attributes.

Solution 2

The person who created the tar file had an effective user ID and group ID (UID:GID) of 1001:1001. Since tar, by default, preserves the ownerships and permissions, when you expand it, you inherit these values. If you have a user with UID:GID 1001:1001 on your system, these files would have been owned by that user.

Comments

[raspacorp]

Ok so this happens only when being root, because if I run the command without sudo: 'tar xzvf nexus-latest-bundle.tar.gz' then the ownership is set to my current user, is that an expected behavior?

[Nate Eldredge]

@raspacorp: As a non-root user, you don't have the authority to create files with any ownership other than your own. So by necessity, the files get created with you as the owner.