deploy/gitbay-runner.override.conf

 1# Drop-in for gitbay-runner.service, installed by `make deploy-runner` to
 2# /etc/systemd/system/gitbay-runner.service.d/override.conf.
 3#
 4# A build must never starve the host: the e2e suite alone starts sixty
 5# daemon instances, and with nothing holding it back a deploy's scp on
 6# the admin sshd stalled at 1%. Lower CPU and IO weight keep sshd,
 7# gitbayd and the backup timers responsive while a build runs.
 8#
 9# These weights are for the service, not per build, so `-jobs N` divides
10# them among N builds rather than taking N times as much. Raising -jobs
11# does not need them raised; it makes each build slower, not the host
12# busier.
13#
14# A build runs whatever the repository's ci.yml says, as the runner's
15# own user. Keep that user unprivileged: its key is added with
16# `keys add --scope runner`, which confines it to the runner protocol
17# and read-only git, and the sandboxing below keeps a step from
18# touching the system outside its workspace.
19#
20# Delegate=yes and the storage path below are what rootless podman needs
21# (#144): it manages its own cgroups for a container, and its image and
22# container store lives under the runner's home, which ProtectSystem
23# would otherwise make read-only. Prepare the host with
24# deploy/runner-podman-setup.sh before deploying a runner that isolates.
25[Service]
26# -cpus 3 of the host's 4 leaves a core for gitbayd and sshd while a build
27# runs. No -memory: the e2e suite peaks past 5GB of the 7GB, and a cap
28# that kills it is an outage rather than a limit (#144).
29#
30# ExecStart is overridden here rather than left in the unit so the flags
31# and the sandboxing that has to match them live in one file: -isolation
32# podman needs NoNewPrivileges=no below, and -image needs an image the
33# host has been given (deploy/runner-podman-setup.sh, Containerfile.ci).
34# podman's run root is pinned under the runner's home by storage.conf
35# (runner-podman-setup.sh), not taken from XDG_RUNTIME_DIR or /tmp: this
36# unit has PrivateTmp, so a /tmp run root is a per-instance tmpfs.
37#
38# The cgroupfs manager puts podman's pause process under the user slice,
39# outside this unit's cgroup, so a stop does not end it and the next
40# start joins its namespaces — including a /tmp that no longer exists.
41# End it with the service.
42ExecStopPost=-/usr/bin/pkill -u ci-runner -x catatonit
43ExecStart=
44ExecStart=/usr/local/bin/gitbay-runner -remote git@127.0.0.1 -workdir /var/lib/gitbay-runner/work -poll 5s -timeout 45m -repos krz/gitbay -isolation podman -image localhost/gitbay-ci:1 -cpus 3
45Nice=10
46CPUWeight=30
47IOWeight=30
48# NoNewPrivileges is off, and that is a deliberate trade (#144).
49#
50# Rootless podman sets up its user namespace with newuidmap, a setuid
51# helper; NoNewPrivileges=yes blocks it and podman fails with
52# "newuidmap: write to uid_map failed: Operation not permitted", so the
53# runner refuses to start. The choice is between this flag and running
54# builds in containers at all.
55#
56# Containers are the stronger boundary by a wide margin. NoNewPrivileges
57# constrained a process that was already executing arbitrary repository
58# code as this user; a container confines that code to an image and a
59# bind-mounted workspace. What is lost is one hardening layer on the
60# runner process itself, which is ours rather than a build's — a build no
61# longer runs in this process's context at all.
62#
63# Under -isolation none there is no container, and this flag should be
64# yes. Set it back if you run that way.
65NoNewPrivileges=no
66ProtectSystem=full
67# ProtectKernelTunables is off, for the same reason NoNewPrivileges is
68# (#144). It overmounts /proc/sys and friends in this unit's namespace,
69# and the kernel then refuses a fresh proc mount in any child user
70# namespace ("mount too revealing"): crun fails with "mount `proc` to
71# `proc`: Operation not permitted". There is no podman setting for it.
72# What the flag protected — /proc/sys from a build running on the host
73# as this user — the container now covers: a build gets its own proc,
74# with those paths masked by the runtime. Under -isolation none, set it
75# back to yes.
76ProtectControlGroups=yes
77RestrictSUIDSGID=yes
78Delegate=yes
79# The runner's home is /var/lib/gitbay-runner (see the Admin page), and
80# the leading - makes a missing path ignored rather than fatal: this
81# drop-in installs on hosts that have not been prepared for podman yet,
82# and a unit that refuses to start would stop every build on the
83# instance.
84ReadWritePaths=-/var/lib/gitbay-runner/.local/share/containers -/var/lib/gitbay-runner/.config/containers