Mount compressed tar file and update it

Question

How do I mount a .tar.gz file, update it (add new files, edit files), and then unmount it such that changes are reflected in the original compressed file?

I'm open to other compression formats if no tools exist to do this for gzipped tar files.

I've tried archivemount, but this mounts .tar.gz files in read-only mode.

Answer 1

By default archivemount works in read-write mode, probably the permissions of the mounted tar.gz file does not allow the user to update it.

Adding "-o debug" to the mount options could help to understand what occurs.

Answer 2

It works fine for me on Fedora 20¹, maybe you have a bug, or as mpromonet suggested, the archive is read-only:

[root@f20 ~]# tar czf /tmp/ul137194.tar.gz -C / /etc/passwd /etc/group /etc/shells
tar: Removing leading `/' from member names
[root@f20 ~]# mkdir /tmp/ul137194
[root@f20 ~]# archivemount /tmp/ul137194.tar.gz /tmp/ul137194
[root@f20 ~]# find /tmp/ul137194
/tmp/ul137194
/tmp/ul137194/etc
/tmp/ul137194/etc/passwd
/tmp/ul137194/etc/group
/tmp/ul137194/etc/shells
[root@f20 ~]# rm /tmp/ul137194/etc/shells
rm: remove regular file ‘/tmp/ul137194/etc/shells’? y
[root@f20 ~]# echo nogroups > /tmp/ul137194/etc/group
[root@f20 ~]# umount /tmp/ul137194
[root@f20 ~]# tar xzf /tmp/ul137194.tar.gz -C /tmp/ul137194
[root@f20 ~]# find /tmp/ul137194
/tmp/ul137194
/tmp/ul137194/etc
/tmp/ul137194/etc/group
/tmp/ul137194/etc/passwd
[root@f20 ~]# cat /tmp/ul137194/etc/group
nogroups

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_{¹archivemount-0.8.1-2.fc20.x86_64, libarchive-3.1.2-7.fc20.x86_64, fuse-2.9.3-2.fc20.x86_64}