The command nixos-container can now create containers. For instance,
the following creates and starts a container named ‘database’:
$ nixos-container create database
The configuration of the container is stored in
/var/lib/containers/<name>/etc/nixos/configuration.nix. After editing
the configuration, you can make the changes take effect by doing
$ nixos-container update database
The container can also be destroyed:
$ nixos-container destroy database
Containers are now executed using a template unit,
‘container@.service’, so the unit in this example would be
‘container@database.service’.
For example, the following sets up a container named ‘foo’. The
container will have a single network interface eth0, with IP address
10.231.136.2. The host will have an interface c-foo with IP address
10.231.136.1.
systemd.containers.foo =
{ privateNetwork = true;
hostAddress = "10.231.136.1";
localAddress = "10.231.136.2";
config =
{ services.openssh.enable = true; };
};
With ‘privateNetwork = true’, the container has the CAP_NET_ADMIN
capability, allowing it to do arbitrary network configuration, such as
setting up firewall rules. This is secure because it cannot touch the
interfaces of the host.
The helper program ‘run-in-netns’ is needed at the moment because ‘ip
netns exec’ doesn't quite do the right thing (it remounts /sys without
bind-mounting the original /sys/fs/cgroups).
These are stored on the host in
/nix/var/nix/{profiles,gcroots}/per-container/<container-name> to
ensure that container profiles/roots are not garbage-collected.
On the host, you can run
$ socat unix:<path-to-container>/var/lib/login.socket -,echo=0,raw
to get a login prompt. So this allows logging in even if the
container has no SSH access enabled.
You can also do
$ socat unix:<path-to-container>/var/lib/root-shell.socket -
to get a plain root shell. (This socket is only accessible by root,
obviously.) This makes it easy to execute commands in the container,
e.g.
$ echo reboot | socat unix:<path-to-container>/var/lib/root-shell.socket -
It is parameterized by a function that takes a name and evaluates to the
option type for the attribute of that name. Together with
submoduleWithExtraArgs, this subsumes nixosSubmodule.
This is a rather large commit that switches user/group creation from using
useradd/groupadd on activation to just generating the contents of /etc/passwd
and /etc/group, and then on activation merging the generated files with the
files that exist in the system. This makes the user activation process much
cleaner, in my opinion.
The users.extraUsers.<user>.uid and users.extraGroups.<group>.gid must all be
properly defined (if <user>.createUser is true, which it is by default). My
pull request adds a lot of uids/gids to config.ids to solve this problem for
existing nixos services, but there might be configurations that break because
this change. However, this will be discovered during the build.
Option changes introduced by this commit:
* Remove the options <user>.isSystemUser and <user>.isAlias since
they don't make sense when generating /etc/passwd statically.
* Add <group>.members as a complement to <user>.extraGroups.
* Add <user>.passwordFile for setting a user's password from an encrypted
(shadow-style) file.
* Add users.mutableUsers which is true by default. This means you can keep
managing your users as previously, by using useradd/groupadd manually. This is
accomplished by merging the generated passwd/group file with the existing files
in /etc on system activation. The merging of the files is simplistic. It just
looks at the user/group names. If a user/group exists both on the system and
in the generated files, the system entry will be kept un-changed and the
generated entries will be ignored. The merging itself is performed with the
help of vipw/vigr to properly lock the account files during edit.
If mutableUsers is set to false, the generated passwd and group files will not
be merged with the system files on activation. Instead they will simply replace
the system files, and overwrite any changes done on the running system. The
same logic holds for user password, if the <user>.password or
<user>.passwordFile options are used. If mutableUsers is false, password will
simply be replaced on activation. If true, the initial user passwords will be
set according to the configuration, but existing passwords will not be touched.
I have tested this on a couple of different systems and it seems to work fine
so far. If you think this is a good idea, please test it. This way of adding
local users has been discussed in issue #103 (and this commit solves that
issue).
libvirtd puts the full path of the emulator binary in the machine config
file. But this path can unfortunately be garbage collected while still
being used by the virtual machine. Then this happens:
Error starting domain: Cannot check QEMU binary /nix/store/z5c2xzk9x0pj6x511w0w4gy9xl5wljxy-qemu-1.5.2-x86-only/bin/qemu-kvm: No such file or directory
Fix by updating the emulator path on each service startup to something
valid (re-scan $PATH).
You can now say:
systemd.containers.foo.config =
{ services.openssh.enable = true;
services.openssh.ports = [ 2022 ];
users.extraUsers.root.openssh.authorizedKeys.keys = [ "ssh-dss ..." ];
};
which defines a NixOS instance with the given configuration running
inside a lightweight container.
You can also manage the configuration of the container independently
from the host:
systemd.containers.foo.path = "/nix/var/nix/profiles/containers/foo";
where "path" is a NixOS system profile. It can be created/updated by
doing:
$ nix-env --set -p /nix/var/nix/profiles/containers/foo \
-f '<nixos>' -A system -I nixos-config=foo.nix
The container configuration (foo.nix) should define
boot.isContainer = true;
to optimise away the building of a kernel and initrd. This is done
automatically when using the "config" route.
On the host, a lightweight container appears as the service
"container-<name>.service". The container is like a regular NixOS
(virtual) machine, except that it doesn't have its own kernel. It has
its own root file system (by default /var/lib/containers/<name>), but
shares the Nix store of the host (as a read-only bind mount). It also
has access to the network devices of the host.
Currently, if the configuration of the container changes, running
"nixos-rebuild switch" on the host will cause the container to be
rebooted. In the future we may want to send some message to the
container so that it can activate the new container configuration
without rebooting.
Containers are not perfectly isolated yet. In particular, the host's
/sys/fs/cgroup is mounted (writable!) in the guest.
Fixes this:
Nov 09 16:18:54 nixos-laptop systemd[1]: Starting Libvirt Virtual Machine Management Daemon...
Nov 09 16:18:54 nixos-laptop dnsmasq[15809]: read /etc/hosts - 2 addresses
Nov 09 16:18:54 nixos-laptop dnsmasq[15809]: failed to load names from /var/lib/libvirt/dnsmasq/default.addnhosts: Permission denied
Nov 09 16:18:54 nixos-laptop dnsmasq[15809]: cannot read /var/lib/libvirt/dnsmasq/default.hostsfile: Permission denied
Nov 09 16:18:55 nixos-laptop systemd[1]: Started Libvirt Virtual Machine Management Daemon.
I don't understand the reason for the original 700 permission bits.
Apparently read-access is needed and Ubuntu also use 755 perms.
Use "chmod" instead of "mkdir -m" to set permissions because mkdir doesn't
modify permissions on existing directories.
(systemd service descriptions that is, not service descriptions in "man
configuration.nix".)
Capitalizing each word in the description seems to be the accepted
standard.
Also shorten these descriptions:
* "Munin node, the agent process" => "Munin Node"
* "Planet Venus, an awesome ‘river of news’ feed reader" => "Planet Venus Feed Reader"
A null password allows logging into local PAM services such as "login"
(agetty) and KDM. That's not actually a security problem for EC2
machines, since they do not have "local" logins; for VirtualBox
machines, if you local access, you can do anything anyway. But it's
better to be on the safe side and disable password-based logins for
root.
Now that overriding fileSystems in qemu-vm.nix works again, it's
important that the VM tests that add additional file systems use the
same override priority. Instead of using the same magic constant
everywhere, they can now use mkVMOverride.
http://hydra.nixos.org/build/6695561
Virsh/virt-manager uses ssh to connect to master, there it expects openbsd netcat(which
has support for unix sockets) to be avalible, to make a tunnel.
Close#1087.
It requires a writable /nix/store to store the build result. Also,
wait until we've reached multi-user.target before doing the build, and
do a sync at the end to ensure all data to $out is properly written.
http://hydra.nixos.org/build/6496716
