Commits on Aug 31, 2019

1. nixos/tests/systemd: Fix x-initrd-mount flakiness (#67798) …

   It turns out that checking for the last mount time of an ext4 file
   system isn't a very reliable way to check whether the file system was
   properly unmounted.
   
   When creating that test in the first place (88530e0),
   I was reluctant to inspect the file system when the VM is down and was
   searching for a way to check for a clean unmount *after* the file system
   was mounted again to make sure we don't need to create a 512 MB raw
   image on the host.
   
   Fortunately however, when converting from qcow2, qemu-img actually
   writes a sparse file, so for most file systems (that is, file systems
   supporting sparse files) this shouldn't waste a lot of disk space.
   
   So when investigating the flakiness, I found that whenever the test is
   failing, the unmount of /test-x-initrd-mount was done *before* the final
   step during which systemd remounts+unmounts all the remaining file
   systems.
   
   I haven't investigated why this is the case, but the test is a
   regression test for #35268, which
   actually didn't unmount the file system *at* *all*, so really all we
   need to take care here is whether the unmount has happened and not
   *how*.
   
   To make sure that checking the filesystem state is enough for this, I
   temporarily replaced the $machine->shutdown call with $machine->crash
   and verified that the file system state is "not clean".
   
   Signed-off-by: aszlig <aszlig@nix.build>
   Fixes: #67555

   

   aszlig authored and disassembler committed Aug 31, 2019
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