The `root_authorized_keys` variable was originally defined only for the
*pyrocufflink* group. This used to effectively be "all" machines, since
everything was a member of the AD domain. Now that we're moving away
from that deployment model, we still want to have the break-glass
option, so we need to define the authorized keys for the _all_ group.
In the spirit of replacing bloated tools with unnecessary functionality
with smaller, more focused alternatives, we can use `doas` instead of
`sudo`. Originally, it was a BSD tool, but the Linux port supports PAM,
so we can still use `pam_auth_ssh_agent` for ppasswordless
authentication.
The Samba AD domain performs two important functions: centralized user
identity mapping via LDAP, and centralized authentication via
Kerberos/GSSAPI. Unfortunately, Samba, on both domain controllers and
members, is quite frustrating. The client, _winbind_, frequently just
stops working and needs to have its cache flushed in order to resolve
user IDs again. It also takes quite a lot of memory, something rather
precious on Raspberry Pis. The DC is also somewhat flaky at times, and
cumbersome to upgrade. In short, I really would like to get rid of as
much of it as possible.
For most use cases, OIDC can replace Kereros. For SSH specifically, we
can use SSH certificates (which are issued to OIDC tokens).
Unfortunately, user and group accounts still need ID numbers assigned,
which is what _winbind_ does. In reality, there's only one user that's
necessary: _dustin_. It doesn't make sense to bring along all the
baggage of Samba just to map that one account. Instead, it's a lot
simpler and more robust to create it statically.
*dnf-automatic* is an add-on for `dnf` that performs scheduled,
automatic updates. It works pretty much how I would want it to:
triggered by a systemd timer, sends email reports upon completion, and
only reboots for kernel et al. updates.
In its default configuration, `dnf-automatic.timer` fires every day. I
want machines to update weekly, but I want them to update on different
days (so as to avoid issues if all the machines reboot at once). Thus,
the _dnf-automatic_ role uses a systemd unit extension to change the
schedule. The day-of-the-week is chosen pseudo-randomly based on the
host name of the managed system.
Promtail is the log sending client for Grafana Loki. For traditional
Linux systems, an RPM package is available from upstream, making
installation fairly simple. Configuration is stored in a YAML file, so
again, it's straightforward to configure via Ansible variables. Really,
the only interesting step is adding the _promtail_ user, which is
created by the RPM package, to the _systemd-journal_ group, so that
Promtail can read the systemd journal files.
The `TrustedUserCAKeys` setting for *sshd(8)* tells the server to accept
any certificates signed by keys listed in the specified file.
The authenticating username has to match one of the principals listed in
the certificate, of course.
This role is applied to all machines, via the `base.yml` playbook.
Certificates issued by the user CA managed by SSHCA will therefore be
trusted everywhere. This brings us one step closer to eliminating the
dependency on Active Directory/Samba.
The *ssh-host-certs* role, which is now applied as part of the
`base.yml` playbook and therefore applies to all managed nodes, is
responsible for installing the *sshca-cli* package and using it to
request signed SSH host certificates. The *sshca-cli-systemd*
sub-package includes systemd units that automate the process of
requesting and renewing host certificates. These units need to be
enabled and provided the URL of the SSHCA service. Additionally, the
SSH daemon needs to be configured to load the host certificates.
*dns1.pyrocufflink.blue* has been decommissioned. Having a second DNS
server never really worked correctly for some reason, and the
maintenance overhead of the Raspberry Pi is just not worth it right now.
The DHCP service has been moved to *dns0.pyrocufflink.blue*.
Dustin