We hit page allocation failures a lot at random for VM tests, in case of
my own Hydra when it comes to the installer tests. The reason for this
is that once the memory of the VM gets heavily fragmented the kernel is
unable to allocate new pages.
Setting vm.min_free_kbytes to 16MB forces the kernel to keep a minimum
of 16 MB free.
I've done some testing accross repeated runs of the installer tests with
and without vm.min_free_kbytes set. So accross 30 test runs for each
settings, all of the tests with the option being set passed while 14
tests without that sysctl option triggered page allocation failures.
Sure, running 30 tests is not a guarantee that 16MB is enough, but we'll
see how it turns out in the long run across all VM tests.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Regression introduced in f496c3cbe4.
Previously when we used security.initialRootPassword, the default
priority for this option was 1001, because it was a default value set by
the option itself.
With the mentioned commit, it is no longer an option default but a
mkDefault, which is priority 1000.
I'm setting this to 150 now, as test-instrumentation.nix is using this
for overriding other options and because I think it still makes it
possible to simple-override it, because if no priority is given, we get
priority 100.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
The attribute ‘config.systemd.services.<service-name>.runner’
generates a script that runs the service outside of systemd. This is
useful for testing, and also allows NixOS services to be used outside
of NixOS. For instance, given a configuration file foo.nix:
{ config, pkgs, ... }:
{ services.postgresql.enable = true;
services.postgresql.package = pkgs.postgresql92;
services.postgresql.dataDir = "/tmp/postgres";
}
you can build and run PostgreSQL as follows:
$ nix-build -A config.systemd.services.postgresql.runner -I nixos-config=./foo.nix
$ ./result
This will run the service's ExecStartPre, ExecStart, ExecStartPost and
ExecStopPost commands in an appropriate environment. It doesn't work
well yet for "forking" services, since it can't track the main
process. It also doesn't work for services that assume they're always
executed by root.
