[Bug 1824236] Re: supermin/liguestfs fails to configure network

[Ioanna Alifieraki]

Thanks Eric for reviewing the debdiffs.

To answer your question I need to take a step back and explain how the supermin appliance
is created and used, at least to the extend I've understood.
Supermin appliances are tiny appliances similar to a virtual machines.
Libguestfs tools depend on supermin to access and modify disk images.
For example, in the test case of the bug description guestfish lunches a supermin
appliance to mount the xenial disk image and operate on it.

The patch concerns the appliance and not the host system; it removes the resolved 
hook from the appliance tree.
When libguestfs package is built some packages are copied from the host (along with 
their dependencies) to be included in the supermin appliance.
Although systemd is not used inside the appliance it is listed into these packages
and exists in the appliance.
This is how we end up with the resolved hook in Ubuntu.
Given that systemd is not used by the appliance removing the hook should not be 
an issue.
AFAIK this hook exists only in Ubuntu, so on any other distro this patch will
try to remove a non-existing file from the appliance, it will fail silently and
execution will continue without affecting the functionality of the appliance.

I tried to do what you suggest, first checking whether we run on Ubuntu and then
remove the hook.
However, this wouldn't work because the files which tell us the distro such as 
/etc/lsb-release is not present in the appliance.
The appliance copies in some files from the build host and some from the host at
runtime, however it does not copy in all of them.
It is similar to the case in LP #1650740 where the /etc/fstab file was missing.

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https://bugs.launchpad.net/bugs/1824236

Title:
  supermin/liguestfs fails to configure network

Status in libguestfs package in Ubuntu:
  In Progress
Status in supermin package in Ubuntu:
  Invalid
Status in libguestfs source package in Bionic:
  In Progress
Status in supermin source package in Bionic:
  Invalid
Status in libguestfs source package in Cosmic:
  In Progress
Status in supermin source package in Cosmic:
  Invalid
Status in libguestfs source package in Disco:
  In Progress
Status in supermin source package in Disco:
  Invalid

Bug description:
  [Impact]
  libguestfs cannot configure network on Bionic onward.

  This bug is a combination of libguestfs/supermin package and
  /etc/dhcp/dhclient-enter-hooks.d/resolved script from systemd,
  present on Bionic onward.
  When supermin creates the appliance does chroot and executes its init script.
  If networking is enabled init will call dhclient sript to configure the network.

  On Bionic onward the make_resolv_conf function of dhclient_script is overwritten
  in /etc/dhcp/dhclient-eneter-hooks.d/resolved which before exiting restarts
  the systemd.resolved service.
  However, this happening in chroot environment fails with
  "System has not been booted with systemd as init system (PID 1). Can't operate."
  and network is left unconfigured.

  [Test Case]

  $ sudo guestfish -a xenial-server-cloudimg-amd64-disk1.img --network -v << EOF
  run
  mount /dev/sda1 /
  command 'apt update'
  EOF

  libguestfs: launch: program=guestfish
  libguestfs: launch: version=1.36.13
  libguestfs: launch: backend registered: unix
  libguestfs: launch: backend registered: uml
  libguestfs: launch: backend registered: libvirt
  ...
  supermin: deleting initramfs files
  supermin: chroot
  Starting /init script ...
  ...
  + dhclient --version
  + dhclient eth0
  System has not been booted with systemd as init system (PID 1). Can't operate.
  ...
  commandrvf: apt update

  WARNING: apt does not have a stable CLI interface. Use with caution in
  scripts.

  W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Temporary failure resolving 'archive.ubuntu.com'
  W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease  Temporary failure resolving 'archive.ubuntu.com'
  W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease  Temporary failure resolving 'archive.ubuntu.com'
  W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
  W: Some index files failed to download. They have been ignored, or old ones used instead.
  ...

  [Regression Potential]

  Minimal. The fix removes the /etc/dhcp/dhclient-eneter-hooks.d/resolved hook installed by systemd.
  systemd is not used inside the appliance so it should not cause any regression.

  
  [Other]

  Affects B,C,D,E.

  Upstream fix :
  https://github.com/libguestfs/libguestfs/commit/2bb6be333e6347d3f18856627d8ad8e50b8e5427

  
  Workaround

  1) Assume that libguestfs is installed, if not :
  $ sudo apt-get install libguestfs-tools

  2) Move the base.tar.gz to a temp dir, extract and remove tarball
  $ sudo mv /usr/lib/x86_64-linux-gnu/guestfs/supermin.d/base.tar.gz ~/tempdir/
  $ cd ~/tempdir
  $ sudo tar -xzvf base.tar.gz
  $ sudo rm base.tar.gz

  3) Remove the etc/dhcp/dhclient-enter-hooks.d/resolved file
  $ sudo rm etc/dhcp/dhclient-enter-hooks.d/resolved

  4) Create tarball again
  $ sudo tar -czvf base.tar.gz etc

  5) Move it back to installation dir
  $ sudo mv base.tar.gz /usr/lib/x86_64-linux-gnu/guestfs/supermin.d/

  6) Clean cache
  $ sudo rm -rf /var/tmp/.guestfs*

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