[systemd-devel] Odd /proc/$pid/fd symlinks in nspawn container

[Mantas Mikulėnas]

Note that devpts also supports multiple instances – the host /dev/pts is
not the same as the guest /dev/pts'en. So my guess is that your stdio is
attached to a pty from the *host*.

Not really sure how that breaks job control though.

Also, the fd symlinks are slightly magical; they can be followed and opened
even if readlink returns garbage. (For example, a socket fd or a pipe fd
wouldn't even *have* a path to return, yet the /proc symlink can be
opened.) So that again shouldn't cause problems.

On Fri, Jul 17, 2015, 11:27 Ben Gamari <ben at smart-cactus.org> wrote:

I have been having quite some trouble getting nspawn give me a shell
with proper job control in a CentOS 6.6 guest. The problem appears to be
that the nodes representing the std{out,err,in} fds in /proc are
malformed,

    $ sudo strace -f -obad systemd-nspawn -D$(realpath centos6.5-amd64)
    Spawning container centos6.5-amd64 on /home/ben/vm/centos6.5-amd64.
    Press ^] three times within 1s to kill container.
    Failed to create directory /home/ben/vm/centos6.5-amd64/sys/fs/selinux:
Read-only file system
    Failed to create directory /home/ben/vm/centos6.5-amd64/sys/fs/selinux:
Read-only file system
    /etc/localtime is not a symlink, not updating container timezone.
    -bash: cannot set terminal process group (-1): Inappropriate ioctl for
device
    -bash: no job control in this shell
    -bash-4.1# ls -lh /proc/self/fd
    total 0
    lrwx------ 1 root root 64 Jul 17 04:14 0 -> /7
    lrwx------ 1 root root 64 Jul 17 04:14 1 -> /7
    lrwx------ 1 root root 64 Jul 17 04:14 2 -> /7
    lr-x------ 1 root root 64 Jul 17 04:14 3 -> /proc/13/fd

Note that fds 0, 1, and 2 all point to a non-existent /7 file. I believe
this should instead point to /dev/pts/7, although strangely this does
not exist either despite /dev/pts being mounted. I am running a very
recent (4.1) kernel.

Am I correct in assuming that this is not expected behavior? What am I
missing here?
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