How to make a tar backup of a root filesystem?

Question

I have linux installed on SD card, I used this command to install the rootfs

tar xpjf rootfs.tar.bz -C /mnt/rootfs/

Now, I made some changes to the rootfs and I would like to create a backup that I can use with the same command above, I tried using:

tar cpjf rootfs.tar.bz2 /mnt/rootfs
and
tar cpjf rootfs.tar.bz2 -C / mnt/rootfs
I also tried
tar cpjf rootfs.tar.bz2 /mnt/rootfs/*

And tried:

cd /mnt/rootfs
tar -cvpjf rootfs.tar.bz2 --exclude=/rootfs.tar.bz2 .
tar: ./rootfs.tar.bz2: file changed as we read it

but I end up with an archive that has two levels before the file system i.e mnt/rootfs/files What am I doing wrong ?

well answered here : https://help.ubuntu.com/community/BackupYourSystem/TAR — Setop, Sep 03 '20 at 17:31

alex88 · Accepted Answer · 2012-07-09T13:02:05.820

14

That's because it starts from current working directory, you can do:

cd /mnt/rootfs
tar cpjf /rootfs.tar.bz2 .

And that should create an archive at /rootfs.tar.bz2 with its root at the contents of /mnt/rootfs/

edited Jul 09 '12 at 13:02

answered Jul 09 '12 at 12:40

alex88

2

Don't use `*`. That might fail with files named like "--filename". Instead, use `./*` . – Ambroz Bizjak Jul 09 '12 at 12:41
Also, it might be worth noting that `./*` (and `*`) might not pick up files whose names begin with a dot. – Ambroz Bizjak Jul 09 '12 at 12:43
Thanks for the tip, i used * as the user posted the question with that, corrected the answer ;) – alex88 Jul 09 '12 at 12:43
@AmbrozBizjak so how do I include hidden files ? – iabdalkader Jul 09 '12 at 12:50
1

@mux `tar cjpf /rootfs.tar.bz2 .` – Ambroz Bizjak Jul 09 '12 at 12:53
@mux the alternative is stuff like `./* ./.*` which you may notice doesn't work quire right, because `./.*` will include `.` and `..`. Another problem with wildcards (`./*`) is that if there's nothing in the folder at all, it will not expand, and tar will try to pack a file named `./*`, which does not exist. – Ambroz Bizjak Jul 09 '12 at 12:55
Thank you all, I just tried installing from the backup and it boots fine. – iabdalkader Jul 09 '12 at 12:55
@alex88 you really should change that to a dot, its the only solution that just works right in all cases – Ambroz Bizjak Jul 09 '12 at 12:59
@AmbrozBizjak I will make another backup just in case, but, just to be clear, the right way to include everything (including hidden files) is tar cjpf /rootfs.tar.bz2 . right ? – iabdalkader Jul 09 '12 at 13:00
10

`tar cpjf /rootfs.tar.bz2 -C /mnt/rootfs .` Where `-C` means "cd into then ...." Is simpler. – sabgenton Aug 14 '13 at 04:16

1 Answers1