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bug#37967: guix environment -CN: Operation not permitted mounting host's
From: |
Ivan Vilata i Balaguer |
Subject: |
bug#37967: guix environment -CN: Operation not permitted mounting host's /var/run/nscd |
Date: |
Mon, 4 Nov 2019 16:23:12 -0500 |
User-agent: |
Mutt/1.12.2 (2019-09-21) |
Ludovic Courtès (2019-11-04 18:07:05 +0100) wrote:
> Ivan Vilata i Balaguer <address@hidden> skribis:
>
> > BTW, I ran that under strace and it looks like the read-only remount fails
> > after mounting `/var/run/nscd` in the new namespace has succeeded:
> >
> > $ strace -f unshare -mUr mount --bind -o ro /var/run/nscd /tmp/tt
> > […]
> > access("/run/mount", R_OK|W_OK) = -1 EACCES (Permission denied)
> > mount("/run/nscd", "/tmp/tt", 0x14c25b0, MS_RDONLY|MS_BIND, NULL) = 0
> > mount("none", "/tmp/tt", NULL, MS_RDONLY|MS_REMOUNT|MS_BIND, NULL) = -1
> > EPERM (Operation not permitted)
> > write(2, "mount: ", 7mount: ) = 7
> > write(2, "/tmp/tt: filesystem was mounted,"..., 89/tmp/tt: filesystem
> > was mounted, but any subsequent operation failed: Unknown error 5005.) = 89
> > write(2, "\n", 1
> > […]
>
> Weird, why does it remount it?
>
> What does:
>
> mount | grep /run
$ mount | grep /run
tmpfs on /run type tmpfs
(rw,nosuid,nodev,noexec,relatime,size=1641444k,mode=755)
[…]
> returns? I just tried on a Debian 10 image with Linux 4.19.0 and /run
> is a tmpfs, which may be the reason why read-only bind-mounts fail (or
> at least there’s a bug in that area.)
>
> Anyway, below is a patch for you to test. Let me know how it goes. :-)
>
> Thanks,
> Ludo’.
I applied your patch on top of bf7b08c4, pulled Guix and did successfully
start `guix environment -CN`, with network support and all.
Cool! `:)`
> diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
> index 6cf6ccc53e..6cdb2b749d 100644
> --- a/gnu/system/file-systems.scm
> +++ b/gnu/system/file-systems.scm
> @@ -507,7 +507,8 @@ a bind mount."
> ;; XXX: On some GNU/Linux systems, /etc/resolv.conf is a
> ;; symlink to a file in a tmpfs which, for an unknown
> reason,
> ;; cannot be bind mounted read-only within the container.
> - (writable? (string=? file "/etc/resolv.conf"))))
> + (writable? (or (string=? file "/etc/resolv.conf")
> + (string=? file "/var/run/nscd")))))
> (cons "/var/run/nscd" %network-configuration-files)))
>
> (define (file-system-type-predicate type)
--
Ivan Vilata i Balaguer -- https://elvil.net/