How do I mount a file on top of a broken symbolic link?

Asked Mar 12 '18 at 12:47

Active Jan 12 '22 at 18:42

Viewed 675 times

In preparation of a chroot I'm doing an mount --bind /etc/resolv.conf ${MOUNTPOINT}/etc/resolv.conf. I need this because the ${MOUNTPOINT} contains a broken etc/resolv.conf.

However, mount is missing the point of the operation. It complains that ${MOUNTPOINT}/etc/resolv.conf "is a symbolic link to nowhere". Yes, I know. That's why I'm doing the rebind in the first place.

[edit] By request, /etc/resolv.conf is a normal file:

-rw-r--r-- 1 root root 42 Feb 6 12:52 /etc/resolv.conf

with normal content

nameserver 192.168.4.1

This should also be used after the chroot, but not by changing the actual ${MOUNTPOINT}/etc/resolv.conf. That should remain as-is:

lrwxrwxrwx 1 root root 27 Jun 14 2017 ${MOUNTPOINT}/etc/resolv.conf -> /run/resolvconf/resolv.conf

(Background: I know about rebinding /run/ in the context of resolv.conf. Doesn't work for me, /etc/resolv.conf is a real file and not a symbolic link. It's only ${MOUNTPOINT}/etc/resolv.conf that's broken, and it's only broken during the chroot so I can't just overwrite it).

edited Jan 12 '22 at 18:42

terdon

242,166

asked Mar 12 '18 at 12:47

MSalters

1

I honestly got lot. Would you add la -la /etc/resolv.conf output to the question? – Rui F Ribeiro Mar 12 '18 at 12:50
@RuiFRibeiro: Are you aware of bind mounts, especially for files? They are a tad obscure, I know. – MSalters Mar 12 '18 at 12:51
I only have used it to mount directories. resolvconf/dnsmask might be getting in your way, and I would not use any of them in a server setting. – Rui F Ribeiro Mar 12 '18 at 12:53
@RuiFRibeiro: resolvconf is indeed getting in my way during the chroot. That's what I'm trying to avoid here. – MSalters Mar 12 '18 at 12:58
I do not use resolvconf in any of my Debian servers. – Rui F Ribeiro Mar 12 '18 at 13:16
why not replacing the link with an actual empty file ? – Kiwy Mar 12 '18 at 13:18
@Kiwy: Because the challenge is not to touch the link. After I'm done with the chroot and have umounted everything, the link should be untouched. – MSalters Mar 12 '18 at 13:35
...good luck ! – don_crissti Mar 12 '18 at 13:44
@don_crissti: That's the source. In my case, the symlink merely happens to be in the place where the bind hides it. But as we know from regular directories used as mount points, Unix & Linux have no problem hiding stuff underneath a mount. – MSalters Mar 12 '18 at 13:54
The point was that when using mount the paths are resolved first (source and destination)... and in your case the destination can't be resolved. – don_crissti Mar 12 '18 at 13:55
Simply copy the /etc/resolv.conf to your chroot. – GAD3R Mar 12 '18 at 14:30
@GAD3R: See question and previous comments. The challenge is NOT to alter the actual file system. – MSalters Mar 12 '18 at 14:32
IMO making r/w mounts weakens a chroot environment. – Rui F Ribeiro Mar 12 '18 at 15:18

How do I mount a file on top of a broken symbolic link?

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