The hardening-extraction subagent (commit just prior) re-introduced
ProcSubset=pid into the server@ drop-in because the design plan's
template had it. The directive had previously been removed from the
live unit by ckn-bw 4339289 — it hides /proc/cpuinfo and breaks
SteamAPI master-server registration, leaving the server in LAN-only
fallback ("LAN servers are restricted to local clients (class C)").
Add a negative assertion in the drop-in test so the regression cannot
sneak back in via a copy-paste edit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Hardening directives leave the base unit body and live in:
deploy/files/etc/systemd/system/left4me-web.service.d/10-hardening.conf
deploy/files/etc/systemd/system/left4me-server@.service.d/10-hardening.conf
Reference units now describe just the base operational shape (exec,
env, restart, resources). Tests split: base-unit content and hardening
profile are asserted separately.
Part of 2026-05-15-deployment-responsibility-design.md migration
step 2. ckn-bw lands the matching reactor surgery + symlink delivery.
Single source of truth for left4me sysctl tuning. The metadata entry
in ckn-bw (sysctl/kernel/yama/ptrace_scope) is removed in lockstep;
the live value is unchanged.
Part of 2026-05-15-deployment-responsibility-design.md migration step 1
(canary).
Sync deployment references for the runtime state relocation
shipped via ckn-bw (commit 6fae2fd). /opt/left4me/ is now a
root-owned deploy-artifact root (just src/); .venv and steamcmd
live at /var/lib/left4me/{.venv,steam}.
Touches:
- deploy/files/.../left4me-web.service: PATH + ExecStart
- deploy/files/.../left4me-workshop-refresh.service: WorkingDirectory
(was /opt/left4me, now /opt/left4me/src to match the web unit),
PATH, ExecStart
- scripts/sbin/left4me wrapper: flask path
- deploy/tests/test_example_units.py: PATH + ExecStart assertions
for the web unit; also fix a pre-existing broken assertion that
read "Environment=PATH=..." (the unit has Environment=HOME=...
PATH=... on one line, so "Environment=PATH=" was never present)
- now reads just "PATH=..."
- deploy/README.md: paths
- l4d2host/tests/test_cli.py: LEFT4ME_STEAMCMD fixture path
Design + as-shipped record:
docs/superpowers/specs/2026-05-15-runtime-state-relocation-design.md.
The original (narrower) prereq spec at
docs/superpowers/specs/2026-05-15-handoff-noneditable-install.md
is marked superseded with a pointer to what shipped + why the
scope grew (setuptools writes egg-info to source during PEP 517
build prep).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Mirrors ckn-bw fix: ProcSubset=pid hides /proc/sys/kernel/random/boot_id,
which journalctl needs at startup; web unit invokes journalctl for
live log streaming.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The hardening refactor that just landed closes the same-uid attack
surface (FS view, ptrace, /proc visibility, signals) for the web +
gameserver units via systemd directives plus system-wide
kernel.yama.ptrace_scope=2. Keeping the script-sandbox on a separate
uid was the inconsistent half-step — defense-in-depth only, with
build-time-idmap complexity attached. One principle wins: harden
once, share the uid.
scripts/libexec/left4me-script-sandbox: drop the idmap block (uid
lookups, STAGING setup, cleanup_staging trap, mount --bind
--map-users), switch User=/Group= to left4me, point BindPaths at
\$OVERLAY_DIR directly. Header comment updated to reflect
hardening-not-uid as the same-uid defense. nsenter self-wrap kept —
it's about mount-namespace escape, not uid.
Tests + comments + companion docs updated. Build-time-idmap and
overlay-idmap plans marked SUPERSEDED; user-uid-split spec revised
to "1 user is correct"; one-line update notes on the hardening
specs and the build-overlay-unit-design.
Companion ckn-bw commit removes the l4d2-sandbox user + group and
tightens /var/lib/left4me from 0711 → 0755 (the traverse-only mode
was specifically for the sandbox uid).
Update the educational reference copies of left4me-server@.service and
left4me-web.service to match the new hardening composition from the
ckn-bw reactor (HARDENING_COMMON + HARDENING_SERVER / HARDENING_WEB).
Per-directive comments explain each defense's purpose and the threat
it addresses, so a cold reader of this repo can understand the threat
model from the unit file alone.
Top-of-file note in each reference points at the ckn-bw reactor as
the live source; reference is hand-synced.
gunicorn ExecStart in the web reference uses placeholder
'--workers 4 --threads 4' values; live emission interpolates from
metadata. This is the documented divergence between the reference
and the deployed unit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Pulls the 5 privileged helpers out of deploy/files/usr/local/{libexec,sbin}/
into top-level scripts/{libexec,sbin}/. They are application-inherent code
(invoked at runtime via sudo from l4d2host/l4d2web), not deploy artifacts —
the previous nesting under deploy/files/ confused source-of-truth with
install-target FHS layout.
deploy/ now means "reference exemplar": README explaining the target
layout, plus example sudoers / sysctl / sandbox-resolv.conf / env
templates / curated systemd units (the ones ckn-bw's reactor emits).
Anyone building a fresh deployment (other than ckn-bw) reads this tree.
Dead static artifacts deleted: left4me-apply-cake helper, left4me-cake
+ left4me-nft-mark service units, cake.env, left4me-mark.nft, and the
superseded deploy-test-server.sh installer.
Tests split to match the new shape:
- scripts/tests/{test_overlay,test_script_sandbox,test_systemctl_helper,
test_journalctl_helper,test_helpers_use_fixed_paths,test_sudoers_grants}.py
with shared fixtures in conftest.py
- deploy/tests/test_example_units.py (renamed from test_deploy_artifacts.py)
— slimmed to lock down the curated example units, sysctl, env templates
l4d2host/tests/test_overlay_helper.py: helper-source path updated to
scripts/libexec/left4me-overlay (was building the path segment-by-segment
under deploy/files/, missed by the path-prefix grep during pre-flight).
Runtime install-target paths (/usr/local/{libexec,sbin}/) unchanged, so
l4d2host/service_control.py, l4d2web/services/overlay_builders.py, the
sudoers grants, and the systemd units all keep their existing path
references.
Requires the matching ckn-bw change to bundles/left4me/items.py
(install_left4me_scripts repointed from /opt/left4me/src/deploy/files/...
to /opt/left4me/src/scripts/...). Left4me lands first so a fresh
git_deploy exposes the new source path before the bundle apply runs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The web service runs with PrivateTmp=true, which puts it in its own
mount namespace. Worker invokes the sandbox helper via sudo from there;
the helper's pre-systemd-run `mount --bind --map-users=...` lands in
the web service's namespace. systemd-run then spawns transient units
in PID 1's namespace where the bind is invisible — the BindPaths lookup
finds an empty staging dir owned by root, and the sandbox uid hits
permission-denied on every write.
Mirror the pattern from left4me-overlay's ExecStartPre wrapper: enter
PID 1's mount namespace at the start of the helper via `nsenter
--mount=/proc/1/ns/mnt`. Sentinel env var avoids exec recursion. The
gameserver helper handles this at the unit level; the script helper
doesn't have a unit so we self-wrap.
Diagnosis: 5 failed builds all hit the same EACCES on the first
`mkdir`/`tar mkdir`. Direct SSH-sudo invocations of the same helper
succeeded because SSH-sudo doesn't inherit a private namespace; only
the worker-invoked path is affected.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
left4me-script-sandbox now pre-creates an idmapped bind staging path
(--map-users=<left4me_uid>:<sandbox_uid>:1) and points the sandbox's
BindPaths at that staging instead of the raw overlay dir. Writes from
inside the sandbox (uid l4d2-sandbox) land on disk as left4me, so all
overlay content is uniformly left4me-owned end-to-end.
left4me-overlay loses ~165 lines of idmap-on-mount logic: the per-
lowerdir stat + idmap-bind setup, the bind-umount loop in teardown,
the uid lookup helpers, the _is_mountpoint /proc/self/mountinfo parser,
and the LEFT4ME_TEST_* env-var stubs. It's back to a simple "validate
lowerdirs, mount overlay" shape; gameserver mount path no longer needs
to know about producer-side ownership decisions.
Verified on kernel 6.12 that the kernel idmap propagates through
systemd-run's plain re-bind of the staging path. Tests dropped 4
idmap-on-mount specs and one deploy-artifact regression check; added
test_script_sandbox_uses_idmap_staging to pin the new staging path
+ map flags + trap cleanup.
The post-build world-read chmod kludge in the sandbox is also dropped:
the web app reads overlay files via its primary uid (left4me).
Existing overlays on the test server are sandbox-owned from prior runs
and need a one-shot `chown -R left4me:left4me /var/lib/left4me/overlays`
during deploy. New overlays produced by the refactored sandbox are
left4me-owned from creation.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
os.path.ismount() compares st_dev against the parent dir, which silently
returns False for same-fs bind mounts. The idmap binds at runtime/<n>/
idmap/<basename> are exactly that case, so:
- cmd_umount skipped the bind-umount step every stop, leaving orphan
binds in PID 1's mount namespace.
- cmd_mount's idempotency check then "didn't see" the orphan and
re-bound on top, accumulating one mount per start/stop cycle.
Findmnt nesting like
/var/lib/left4me/runtime/2/idmap/overlays_9
└─/var/lib/left4me/runtime/2/idmap/overlays_9
is the visible symptom. Reboot wipes everything so the bug is invisible
on a fresh boot — only stop/start cycles accumulate.
Replace both ismount sites with a _is_mountpoint() helper that reads
/proc/self/mountinfo (column 5 is the mount point). Keep os.path.ismount
for the overlay merged check, where it's reliable (distinct fs type).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
ckn-bw was shipping the admin CLI wrapper (sudo left4me <flask
subcommand>) verbatim from its own bundle copy. Move ownership of the
file into left4me so ckn-bw's upcoming install-action approach can
deploy it from deploy/files/usr/local/sbin/left4me on the deployed
git checkout, eliminating the cross-repo duplication that masked the
idmap helper update earlier.
Also re-frame deploy/README.md: deploy/files/, deploy/templates/, and
deploy/tests/ are now genuinely canonical (read by ckn-bw via
git_deploy). Only deploy-test-server.sh remains a superseded artifact.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Spell out that the deploy step for changes to verbatim-shipped files
(privileged helpers, sudoers, sysctl, …) is just re-syncing the bundle's
copy + bw apply. Removes ambiguity for the idmap helper change and any
future edit within the same set.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Guards against silent regression of the idmap bind-mount step in the
privileged kernel-overlayfs helper. Asserts --map-users / --map-groups
argv, the runtime/<name>/idmap/ target path, the LEFT4ME_TEST_* stub-
env-var names, and the collision-detection table.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Issue #1: idmap target now uses parent+name (overlays_workshop instead of
workshop) to prevent basename collisions across allowlist roots; explicit
die() on collision detected in the loop.
Issue #2: env-var uid stubs (renamed to LEFT4ME_TEST_SANDBOX_UID etc.) are
only honoured when LEFT4ME_OVERLAY_PRINT_ONLY=1, so a misconfigured systemd
unit override cannot influence real uid mapping.
Issue #3: os.stat(lowerdir) is wrapped in try/except OSError with a die()
that shell-quotes the path and includes the exception, matching the helper's
existing error style.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Insert an idmapped bind mount in front of each lowerdir whose top-level
uid matches l4d2-sandbox at overlay-mount time, so that overlayfs copy-up
produces left4me-owned upperdir entries instead of EACCES.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
For the live-state panel's Steam profile enrichment (persona names +
avatars). Optional: empty value disables enrichment and the panel falls
back to in-game names + placeholder avatars.
The actual web.env is materialized by the ckn-bw bundle's Mako; the
template here documents the operator-facing shape.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds left4me-workshop-refresh.service (oneshot, triggers flask
workshop-refresh) and left4me-workshop-refresh.timer (04:00 daily,
Persistent=true, 15 min jitter). Wires both into the deploy script's
cp and enable blocks.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
ovh.left4me is now provisioned by the ckn-bw bundle bundles/left4me/
(attached via groups/applications/left4me.py); run `bw apply
ovh.left4me` from there.
Keep this directory verbatim as deployment-knowledge reference: what
was configured, what each unit/helper does, why the privileged
boundaries are drawn the way they are. Add a top-of-README
correspondence table marking which files migrated 1:1 vs. which are
obsolete in the new architecture (CAKE moved to systemd-networkd;
nft marking moved into the central nftables bundle; systemd units
are emitted by a metadata reactor; CPU isolation drop-ins are no
longer managed declaratively).
The deploy-test-server.sh stays here too — useful as a concrete walk-
through of the install steps the bundle now performs declaratively.
Just don't run it against an ovh.left4me node managed by ckn-bw; the
two would fight over file ownership, sudoers, and unit definitions.
Installs nftables via apt/dnf, copies left4me-mark.nft and left4me-apply-cake
helper into system paths, conditionally seeds cake.env (preserving operator
edits), and enables left4me-nft-mark.service + left4me-cake.service on deploy.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The CAKE egress shaper now has a systemd unit that wraps the
left4me-apply-cake helper in apply and clear modes. The unit is a
oneshot that starts after network-online and survives service restarts,
allowing the shaper to persist across reboots and be managed by systemd.
The environment file is marked non-fatal (EnvironmentFile=-) to handle
missing or incomplete configurations gracefully.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
systemd's `+` Exec prefix removes sandbox/credentials but does NOT
detach from the unit's per-service mount namespace (created by
PrivateTmp/Protect*). The Python interpreter for the helper was
launched inside that namespace, and even though the helper internally
nsenter'd into PID 1 for the umount syscall, the calling Python
process itself never left the unit's namespace. Its existence pinned
the namespace alive, which kept the slave mount tree alive, which
made PID 1's umount return EBUSY for the entire duration of the
helper's run. The mount became unmountable the moment the helper
exited — empirically verified by polling /proc/*/ns/mnt during stop:
the only PID holding the dying namespace was the helper itself.
Wrap both ExecStartPre and ExecStopPost with `/usr/bin/nsenter
--mount=/proc/1/ns/mnt --` so the helper Python interpreter runs in
PID 1's mount namespace from the start. With the helper out of the
unit's namespace, umount succeeds first try once the cgroup empties.
Reset went from ~25 s with retry/lazy-fallback workarounds to ~0.5 s
clean.
Knock-on cleanups:
- Helper drops internal nsenter for the syscalls (already in PID 1's
namespace), and drops the eager-retry loop + lazy-umount fallback +
inner work_inner retry (no race left to ride out).
- Revert TimeoutStopSec=60s back to 15s.
- Tests updated to expect the new argv shapes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
srcds_run is a shell script that cd's to its own dirname before exec'ing
srcds_linux, so WorkingDirectory has no effect — the binary's path is what
determines where the engine reads gameinfo.txt and addons from. Pointing
at installation/srcds_run resolved everything against the lower layer, so
overlay-provided Metamod/SourceMod plugins and cfgs (zonemod, confogl)
never loaded. Switch to runtime/%i/merged/srcds_run so the engine sees
the merged tree.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
`test_deploy_script_has_safe_defaults_and_preserves_state` had been red
since commit caa8b83 ("rewrite web.env every deploy with machine-id-
derived SECRET_KEY"). Two assertions encoded the prior model:
- `if [ ! -f /etc/left4me/web.env ]` — the create-only-if-missing guard
caa8b83 removed in favor of unconditional `install -m 0640 ...`.
- `. /etc/left4me/web.env not in script` — masked by the first failing
but also stale: the deploy intentionally sources web.env in the
alembic and seed-script-overlays helper subprocesses so they get
DATABASE_URL.
Removed both. The full suite now runs 0 failed. The note left in place
points future readers at the live coverage path (install + SECRET_KEY
rewrite + run_left4me_with_env plumbing already asserted nearby).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Two bugs surfaced by the previous deploy attempt:
1. l4d2host/pyproject.toml still listed `l4d2host.fs` in the explicit
packages= list. After deleting the fs/ package, pip install -e fails
with "package directory './fs' does not exist".
2. The CPU-isolation deploy step uses `nproc` to detect host core count,
but `nproc` honors Cpus_allowed of the calling shell. On a host that
already has the cpuset drop-ins applied (system.slice/user.slice →
AllowedCPUs=0), the SSH login lands constrained to one core and
`nproc` returns 1 — making subsequent deploys think they're on a
single-core box and skip the cpuset writes entirely. `nproc --all`
reports installed processors regardless of affinity, which is what
the deploy actually wants.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Symmetric with the earlier mount cleanup (commits 519567e..a982995). Until
now, the unit's ExecStartPre handled mount but the Python side still drove
unmount: stop_instance and _purge_instance both called _mounter.unmount,
which wrapped sudo + the helper. Two code paths for two halves of the
same lifecycle.
Move unmount into the unit:
- ExecStopPost=+/usr/local/libexec/left4me/left4me-overlay umount %i
(ExecStopPost, not ExecStop, so it runs after the cgroup is cleared;
ExecStop runs while srcds is alive and would EBUSY the umount syscall.)
- Helper's umount verb is now idempotent (mirrors mount): if merged
isn't a mount point, return early. PRINT_ONLY mode bypasses both
short-circuits so the unit tests still exercise the full nsenter argv.
Drop the dead Python machinery:
- _mounter.unmount(...) calls in stop_instance and _purge_instance
- _mounter global + KernelOverlayFSMounter import
- The whole l4d2host/fs/ package (OverlayMounter ABC + KernelOverlayFSMounter
class) — no production callers, just self-tests
- l4d2host/tests/test_kernel_overlayfs.py
- test_stop_succeeds_when_unmount_fails / test_delete_succeeds_when_unmount_fails
(tested Python-side unmount-failure tolerance that no longer exists)
- The l4d2host.fs.kernel_overlayfs.run_command monkeypatches in lifecycle tests
After this, the only thing start_instance does beyond cfg-staging is ask
systemd to enable+start the unit. stop/delete/reset only ask systemd to
disable; the overlay lifecycle lives entirely in the unit file.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
systemd 230+ moved StartLimitBurst= and StartLimitIntervalSec= from
[Service] into [Unit] (with the rename from StartLimitInterval=). Putting
them in [Service] makes systemd silently ignore them with a warning to
journalctl: "Unknown key 'StartLimitIntervalSec' in section [Service],
ignoring." — meaning the restart-loop cap I claimed in commit 519567e
wasn't actually applied.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The unit has NoNewPrivileges=true (security hardening for srcds), which
blocks sudo's setuid escalation. The previous sudo'd ExecStartPre failed
on every start with "sudo: the 'no new privileges' switch is set, which
prevents sudo from running as root" -> Restart=on-failure loop.
systemd's `+` prefix runs the Exec command as PID 1 (root, no sandbox),
bypassing User=/Group=/NoNewPrivileges=. Equivalent privilege scope to
the sudoers rule the web app already uses for the same helper, just
without the sudo middleman.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Before this change there were two callers of left4me-overlay mount:
the web app's start_instance (Python, in-process) and the unit's
ExecStartPre (shell, via sudo). The duplication invited divergence; the
helper's recently-added idempotency made both paths technically work
but at the cost of a "first wins" race and dead-code retry logic in
start_instance.
Drop the in-process _mounter.mount() call from start_instance. The web
app now only stages cfg files (which still must happen on the host
filesystem before mount, to avoid overlayfs copy-up changing ownership),
then asks systemd to enable+start the unit; the unit's ExecStartPre
does the mount.
Removed:
- os.path.ismount(merged) refusal in start_instance and its test
(test_start_refuses_to_double_mount). The race the check guarded
against is now handled by the helper's idempotency.
- _load_instance_env helper and the `os` import (both became dead).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
systemd applies WorkingDirectory= to every Exec line including ExecStartPre.
With the merged dir not yet existing at boot time (the volatile overlay
mount has been wiped), the chdir into runtime/%i/merged/left4dead2 fails
with status=200/CHDIR before ExecStartPre can run the mount helper.
The `-` prefix makes chdir failure non-fatal: ExecStartPre runs in the
unit's home (cwd doesn't matter for the mount helper); ExecStart re-applies
WorkingDirectory once the mount has landed and chdirs successfully.
Companion to commit 519567e (which added the ExecStartPre mount + helper
idempotency but didn't account for the WorkingDirectory ordering).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The lifecycle change to systemctl enable --now (commit 8552c55) made
units auto-start at boot. But the kernel-overlayfs mount is volatile
(reboot kills it), and the web app's start_instance only re-mounts in
response to a UI click. Result: at boot, systemd starts the unit, finds
empty merged/, CHDIR fails, Restart=on-failure spins forever (counter
hit 65 on ckn before this fix landed).
Fix:
- Unit gets `ExecStartPre=/usr/bin/sudo -n .../left4me-overlay mount %i`
so the overlay is established before the main process starts.
- Helper is now idempotent: if merged is already a mount point, exit 0.
Required because Restart=on-failure re-runs ExecStartPre on each
cycle, and the web-app's start_instance also calls the helper, so
both paths would otherwise collide on "already mounted".
- StartLimitBurst=5 + StartLimitIntervalSec=60s caps the restart loop
instead of letting it spin indefinitely on a fundamental failure.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Servers started via the web UI now create a WantedBy= symlink under
multi-user.target.wants/, so they auto-start on the next host reboot.
Helper verbs renamed start/stop -> enable/disable; service_control.py
renamed start_service/stop_service -> enable_service/disable_service.
The user-facing l4d2ctl start/stop commands keep their names per the
AGENTS.md contract -- only the implementation changes. Spec:
docs/superpowers/specs/2026-05-09-l4d2-server-lifecycle-reboot-and-drift-design.md
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Explains the core-0-vs-game-cores split, the LEFT4ME_SYSTEM_CPUS /
LEFT4ME_GAME_CPUS overrides, the single-core skip, and the
subset-of relationship with per-instance CPUAffinity=.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Computes NPROC at deploy time. Defaults LEFT4ME_SYSTEM_CPUS=0 and
LEFT4ME_GAME_CPUS=1-(NPROC-1). Single-core hosts skip cpuset writes
with a stderr warning unless an env var override is set. Spec:
docs/superpowers/specs/2026-05-09-l4d2-cpu-isolation-design.md
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
- RT example: add AmbientCapabilities=CAP_SYS_NICE so the User=left4me
service can actually enter SCHED_FIFO on Trixie.
- CPU governor: note that linux-cpupower may need apt install.
- CPUAffinity=2: clarify that per-instance values typically increment.
- NIC tuning: note that ethtool may need apt install.
Documents CPU governor, per-instance CPUAffinity, NIC tuning, and
SCHED_FIFO opt-in patterns. None of these are auto-applied; they're
ops-side knobs for measured problems the perf baseline doesn't solve.
Copies l4d2-game.slice and l4d2-build.slice into
/usr/local/lib/systemd/system/, installs 99-left4me.conf into
/etc/sysctl.d/, and runs sysctl --system so the perf baseline is
live this deploy, not on next reboot.
Builds yield CPU/IO to game-server instances under contention via the
slice's weight=10, and are killed first under memory pressure
(servers have OOMScoreAdjust=-200).
Matches the spec-pointer comment Task 1 added to
left4me-server@.service. A future operator running
`systemctl cat l4d2-game.slice` now finds the rationale.
Flat top-level slices. Game wins under contention; build still gets
the box when uncontended. Referenced by left4me-server@.service and
the script-sandbox systemd-run invocation.
