No network in chroot environment

[Tom H]

On Fri, Jan 24, 2020 at 7:16 PM Volker Wysk <post at volker-wysk.de> wrote:
>
> I'm migrating my old system to a new SSD in a new computer, and come to
> the point to set up the new root file system in a chroot:
>
> cryptsetup luksOpen /dev/nvme0n1p3 nvme0n1p3_crypt
> mount /dev/mapper/nvme0n1p3_crypt /mnt/rootneu
> mount --rbind /dev /mnt/rootneu/dev
> mount --rbind /proc /mnt/rootneu/proc
> mount --rbind /sys /mnt/rootneu/sys
> mount /dev/nvme0n1p2 /mnt/rootneu/boot
> mount /dev/nvme0n1p1 /mnt/rootneu/boot/efi
> chroot /mnt/rootneu
>
> This works, but the network in the chroot-ed environment isn't
> available:
>
> Wartung1804 / % LANG=C ping heise.de
> ping: heise.de: Name or service not known
>
> In the original system, it's fine:
> v at Wartung1804:~$ LANG=C ping heise.de
> PING heise.de(redirector.heise.de (2a02:2e0:3fe:1001:302::)) 56 data
> bytes
> 64 bytes from redirector.heise.de (2a02:2e0:3fe:1001:302::): icmp_seq=1
> ttl=57 time=15.0 ms
> ...
>
> So what happened to the network..? Might the "mount --rbind ..."
> commands be incomplete?

"/etc/resolv.conf" is probably a dangling symlink. One option might be
to copy "/run/.../resolv.conf" to the chroot before chrooting.

I wonder whether bind-mounting "/run" would work and wouldn't have any
downsides. I've never tried it; I've never even tnought of it before!

PS: "/proc" isn't usually bind-mounted.

PPS: There's a recommendation to make the bind-mounted filesystems
slaves for systemd.

PPPS: I use for Gentoo/Funtoo

mount -t proc proc "$mountpoint"/proc

for apifs in dev sys ; do
mount -o rbind /"$apifs" "$mountpoint"/"$apifs"
mount --make-rslave "$mountpoint"/"$apifs"
done

AFAIR, the Arch installer doesn't bind-mount any of the API
filesystems (e.g. 'mount -t sys sys "$mountpoint"/sys' for sysfs).