feat(install): offer /tmp on disk + SSH memory guard, deploy cloudpex helper

/tmp is a RAM-backed tmpfs on Ubuntu (50% of RAM). Agent runs fill it: half
the RAM goes, then every temp-file creation fails with ENOSPC and shells
break. Swap does not lift the cap, so the fix is /tmp on disk.

End-of-install offers (Linux, [y/N], skipped without a terminal, idempotent):
- offer_tmp_on_disk: mask tmp.mount + etc/tmpfiles.d/tmp.conf (wipe at
  boot, 10-day purge, /var/tmp rule kept). Effective at next reboot.
- offer_ssh_memory_guard: the previous server's rules. ssh.service drop-in
  (OOMScoreAdjust=-1000, MemoryMin=256M) + earlyoom with --avoid sshd and
  --prefer node/java. MemoryMin covers sshd only; earlyoom is the real guard.

install_cloudpex deploys the NAS mount helper in the Linux block.
Docs: README steps 12-14 + table, CLAUDE.md layout + lint command.

.claude/tasks/TODO.md

@@ -25,3 +25,19 @@
 - [ ] Runtime-test install.sh on a clean VM (all 4 targets) — not safe on dev machine
 - [ ] Consider an `uninstall.sh` (restore from ~/Oldconfig)
 - [x] LICENSE if repo ever goes public — done (GPL-3.0, BDR-008, 40c6524)
+
+## Feature — /tmp on disk + SSH OOM guard + cloudpex installer (2026-09-22)
+Branch: feature/tmp-disk-ssh-oom-cloudpex (off develop). Design approved in chat (bounded).
+Root cause: /tmp is tmpfs (50% RAM) → agents fill it → RAM halved + ENOSPC breaks shells. Swap rejected.
+- [x] etc/tmpfiles.d/tmp.conf (D /tmp 10d + q /var/tmp 30d — keep both upstream lines)
+- [x] etc/systemd/ssh.service.d/override.conf (MemoryMin=256M, OOMScoreAdjust=-1000 — old server)
+- [x] etc/default/earlyoom (old server args: -r 60 -m 10 -s 10 --avoid sshd… --prefer node…)
+- [x] install.sh: confirm() TTY-guarded prompt helper
+- [x] install.sh: offer_tmp_on_disk() — mask tmp.mount + tmpfiles rule, reboot notice, idempotent
+- [x] install.sh: offer_ssh_memory_guard() — drop-in + daemon-reload/restart ssh + earlyoom, idempotent
+- [x] install.sh: install_cloudpex() in Linux block; offers at end of script (Linux-gated)
+- [x] cloudpex/install.sh — /usr/local/bin/cloudpex root 0755, /mnt/cloudpex, cifs-utils if missing
+- [x] cloudpex/README.md (FR) — purpose, why on-demand not fstab, usage, install
+- [x] README.md steps 12-14 + table rows; CLAUDE.md layout
+- [x] shellcheck + bash -n (install.sh, cloudpex/install.sh); stub-sudo dry run of the offers
+- [x] commit on feature branch (no gitea-deploy/, no .githooks changes)

CLAUDE.md

@@ -23,9 +23,16 @@ vim/colors/           molokai colorscheme (committed)
 bash/bashrc-{linux,osx}          OS-detected bashrc
 bin/{dt,dtach-router,claude-provider}   CLI scripts deployed to ~/.local/bin
 etc/profile.d/disk-usage-warning.sh     login-time low-disk warning → /etc/profile.d (Linux only)
+etc/tmpfiles.d/tmp.conf                 disk-backed /tmp cleanup rules (offer: /tmp on disk)
+etc/systemd/ssh.service.d/override.conf sshd OOM-exempt drop-in (offer: SSH memory guard)
+etc/default/earlyoom                    earlyoom args, spare sshd / kill node first (same offer)
+cloudpex/{cloudpex,install.sh,README.md} on-demand CloudPex SMB mount helper → /usr/local/bin (FR docs)
 .claude/{tasks,memory,audits}/   Claude working state
 ```
 
+`/tmp` is a RAM-backed tmpfs on Ubuntu (50% of RAM): agent runs fill it, which is why
+install.sh offers to mask `tmp.mount`. Swap is not the fix (the cap and ENOSPC stay).
+
 `pymupdf`/`markdown_py` are NOT tracked — they are pipx entry-point shims,
 recreated by `pipx install PyMuPDF Markdown` in install.sh.
 `claude-provider` reads `$OPENROUTER_API_KEY` from the env — never hardcode it (the
@@ -35,8 +42,8 @@ original had a live key; it was scrubbed — see decisions/blockers).
 
 | Task  | Command                                  |
 | ----- | ---------------------------------------- |
-| Lint  | `shellcheck *.sh bash/bashrc-*`          |
+| Lint  | `shellcheck *.sh cloudpex/install.sh cloudpex/cloudpex bash/bashrc-*` |
-| Syntax check | `bash -n install.sh remote-install.sh` |
+| Syntax check | `bash -n install.sh remote-install.sh cloudpex/install.sh` |
 | Install | `./install.sh` (OS auto-detected) |
 | Remote install | `curl -fsSL <raw>/remote-install.sh \| bash` |
 

README.md

@@ -16,7 +16,11 @@ curl -fsSL https://git.bchanot.fr/bchanot/config/raw/branch/master/remote-instal
 
 | Path                 | Purpose                                                        |
 | -------------------- | -------------------------------------------------------------- |
-| `install.sh`         | Installs apt packages + Docker + code-server + RDP (gnome-remote-desktop), backs up old config, deploys vim + bashrc (OS-detected), installs CLI scripts, pipx tools, and a low-disk login warning. |
+| `install.sh`         | Installs apt packages + Docker + code-server + RDP (gnome-remote-desktop), backs up old config, deploys vim + bashrc (OS-detected), installs CLI scripts, pipx tools, a low-disk login warning and the `cloudpex` NAS mount helper; ends by offering two system changes (`/tmp` on disk, SSH memory guard). |
+| `cloudpex/`          | On-demand SMB mount of the CloudPex NAS share (`cloudpex` command + its installer). French README inside. |
+| `etc/tmpfiles.d/tmp.conf` | Cleanup rules for a disk-backed `/tmp` (wiped at boot, 10-day purge). Deployed by the `/tmp` on disk offer. |
+| `etc/systemd/ssh.service.d/override.conf` | `ssh.service` drop-in: sshd exempt from the OOM killer + memory reclaim protection. Deployed by the SSH memory guard offer. |
+| `etc/default/earlyoom` | earlyoom arguments: spare sshd/systemd, kill node/java first. Deployed by the SSH memory guard offer. |
 | `vim/vimrc`          | Vim config: pathogen, molokai, syntastic (C with `-Wall -Werror -Wextra`), NERDTree, 42-style canonical class generators (`:ClassH`, `:ClassC`). |
 | `vim/autoload/`      | `pathogen.vim` plugin loader (committed).                      |
 | `vim/colors/`        | `molokai.vim` colorscheme (committed).                         |
@@ -61,6 +65,9 @@ What it does:
 9. On Linux, installs `etc/profile.d/disk-usage-warning.sh` to `/etc/profile.d/` (needs `sudo`) so each login warns when `/` or `/home` cross 85% usage.
 10. On Linux, installs **code-server** (VS Code in the browser) via its vendor script — skipped if already present — and enables the `code-server@$USER` systemd service.
 11. On Linux, sets up **RDP remote login** via `gnome-remote-desktop` (Wayland-native): installs the daemon + `openssl`, generates a self-signed TLS cert once, and prompts interactively for shared "gate" credentials (skipped when no terminal is attached, or already set). Disables `xrdp` if present; opens UFW port `3389` only when UFW is already active.
+12. On Linux, installs the **`cloudpex`** NAS mount helper to `/usr/local/bin` via `cloudpex/install.sh` (nothing is mounted, no credential stored, see [`cloudpex/README.md`](cloudpex/README.md)).
+13. On Linux, at the very end, **offers** (`[y/N]`, skipped when no terminal is attached) to move **`/tmp` to disk**: Ubuntu mounts `/tmp` as a RAM-backed tmpfs capped at 50% of RAM, which agent runs fill, halving the RAM and breaking every shell with "No space left on device". Accepting masks `tmp.mount` and installs `etc/tmpfiles.d/tmp.conf` (wipe at boot, 10-day purge). Effective at the next reboot.
+14. On Linux, at the very end, **offers** to keep **SSH reachable under memory pressure**: installs the `ssh.service` drop-in (`OOMScoreAdjust=-1000`, `MemoryMin=256M`) and `earlyoom` with `etc/default/earlyoom` (kills the largest process, `node`/`java` first and never `sshd`, once free RAM and swap both drop under 10%). Restarting `ssh` keeps open sessions. Note: `MemoryMin` protects the sshd daemon only; login sessions live in `user.slice`, so no setting can reserve RAM for a future shell. earlyoom acting in time is the real protection.
 
 ### Packages installed (apt)
 
@@ -72,6 +79,7 @@ What it does:
 - **Docker**: `docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin` (via Docker's repo)
 - **Remote access**: `gnome-remote-desktop openssl` (apt) + `code-server` (via its vendor install script, not apt) — RDP remote login + browser VS Code
 - **pipx**: `PyMuPDF` (`pymupdf`), `Markdown` (`markdown_py`)
+- **Optional (end-of-install offer, Linux)**: `earlyoom`
 
 The script is re-runnable: each run re-backs up to `~/Oldconfig` (overwriting the previous backup), re-clones plugins, skips Docker if already installed, and re-deploys the `bin/` scripts.
 

etc/default/earlyoom

@@ -0,0 +1,8 @@
+# earlyoom settings, sourced by earlyoom.service (rules of the previous server).
+# -r 60     memory report in the journal every minute
+# -m 10     act when available RAM drops under 10% ...
+# -s 10     ... and free swap under 10% (both conditions)
+# --avoid   never kill sshd, systemd, logind, dbus, containerd
+# --prefer  kill the agent runtimes first: java, node, pnpm, esbuild
+# Quotes inside the value are honoured by systemd's $VAR word splitting.
+EARLYOOM_ARGS="-r 60 -m 10 -s 10 --avoid '^(sshd|systemd|systemd-logind|dbus-daemon|containerd)$' --prefer '^(java|node|pnpm|esbuild)$'"

etc/systemd/ssh.service.d/override.conf

@@ -0,0 +1,8 @@
+# ssh.service drop-in: keep sshd alive when RAM runs out (rules of the previous server).
+# OOMScoreAdjust=-1000  the kernel OOM killer never selects sshd.
+# MemoryMin=256M        reclaim protection for the daemon's own cgroup. Login sessions
+#                       live in user.slice (logind), so this cannot reserve RAM for an
+#                       interactive shell — earlyoom is what frees memory in time.
+[Service]
+MemoryMin=256M
+OOMScoreAdjust=-1000

etc/tmpfiles.d/tmp.conf

@@ -0,0 +1,5 @@
+# /tmp on disk (install.sh masks tmp.mount): keep the tmpfs semantics — wipe /tmp
+# at boot (D) and purge entries untouched for 10 days. Same file name as
+# /usr/lib/tmpfiles.d/tmp.conf, so this REPLACES it: the /var/tmp rule must stay.
+D /tmp 1777 root root 10d
+q /var/tmp 1777 root root 30d

install.sh

@@ -133,6 +133,87 @@ unwire_dtach_profile() {
 	' "$profile" > "$profile.tmp" && mv "$profile.tmp" "$profile"
 }
 
+# NAS helper: deploys the on-demand CloudPex SMB mount command to /usr/local/bin
+# (see cloudpex/README.md). Nothing is mounted and no credential is stored.
+# Linux-only (cifs-utils); the helper's own installer is idempotent.
+install_cloudpex() {
+	echo "Installing the cloudpex mount helper"
+	bash "$SCRIPT_DIR/cloudpex/install.sh"
+}
+
+# Yes/no prompt for the optional system changes offered at the end of the install.
+# Declines (returns 1) when no terminal is attached (curl | bash), so an offer is
+# skipped with a hint instead of blocking; re-run ./install.sh from a terminal to
+# get it offered again.
+confirm() {
+	local answer=""
+	if [ ! -t 0 ]; then
+		echo "Skipped (no terminal attached): $1" >&2
+		return 1
+	fi
+	read -rp "$1 [y/N] " answer || true
+	case "$answer" in
+		[yY]|[yY][eE][sS]) return 0 ;;
+		*) return 1 ;;
+	esac
+}
+
+# /tmp on disk instead of the tmpfs Ubuntu mounts by default (RAM-backed, capped at
+# 50% of RAM). Agent runs fill it: that eats half the RAM and, once the cap is hit,
+# every temp-file creation fails with ENOSPC — which is what breaks shells. Masking
+# tmp.mount leaves /tmp on the root filesystem; the tmpfiles rule keeps the tmpfs
+# semantics (wiped at boot, entries older than 10 days purged). Takes effect at the
+# next reboot: a busy /tmp is never unmounted live. Idempotent.
+offer_tmp_on_disk() {
+	if [ "$(systemctl is-enabled tmp.mount 2>/dev/null)" = "masked" ]; then
+		echo "/tmp already on disk (tmp.mount masked) — skipping"
+		return 0
+	fi
+	if [ "$(findmnt -n -o FSTYPE -T /tmp)" != "tmpfs" ]; then
+		echo "/tmp is not a tmpfs — nothing to do"
+		return 0
+	fi
+	confirm "Move /tmp from RAM (tmpfs) to disk? Agents fill it and break shells" || return 0
+	sudo systemctl mask tmp.mount
+	sudo install -D -m 0644 "$SCRIPT_DIR/etc/tmpfiles.d/tmp.conf" /etc/tmpfiles.d/tmp.conf
+	echo "/tmp moves to disk at the next reboot."
+}
+
+# Keep SSH reachable when RAM runs out — the two rules the previous server ran:
+#  - ssh.service drop-in: OOMScoreAdjust=-1000 (the kernel OOM killer never picks
+#    sshd) + MemoryMin=256M (reclaim protection for the daemon's cgroup);
+#  - earlyoom: kills the single largest process (node preferred, sshd/systemd spared)
+#    once free RAM and free swap both drop under 10%, before the box thrashes.
+# MemoryMin covers sshd only: logind puts login sessions in user.slice, so nothing can
+# reserve RAM for a future shell — earlyoom acting in time is the real protection.
+# Idempotent: each piece is skipped when already in place. Restarting ssh keeps the
+# current sessions alive (KillMode=process).
+offer_ssh_memory_guard() {
+	local dropin="/etc/systemd/system/ssh.service.d/override.conf"
+	local ssh_done=0 oom_done=0
+	cmp -s "$SCRIPT_DIR/etc/systemd/ssh.service.d/override.conf" "$dropin" && ssh_done=1
+	if cmp -s "$SCRIPT_DIR/etc/default/earlyoom" /etc/default/earlyoom \
+		&& [ "$(systemctl is-enabled earlyoom 2>/dev/null)" = "enabled" ]; then
+		oom_done=1
+	fi
+	if [ "$ssh_done" = 1 ] && [ "$oom_done" = 1 ]; then
+		echo "SSH memory guard already in place — skipping"
+		return 0
+	fi
+	confirm "Protect SSH under memory pressure (sshd OOM-exempt + earlyoom)?" || return 0
+	if [ "$ssh_done" = 0 ]; then
+		sudo install -D -m 0644 "$SCRIPT_DIR/etc/systemd/ssh.service.d/override.conf" "$dropin"
+		sudo systemctl daemon-reload
+		sudo systemctl restart ssh
+	fi
+	if [ "$oom_done" = 0 ]; then
+		sudo apt-get install -y earlyoom
+		sudo install -m 0644 "$SCRIPT_DIR/etc/default/earlyoom" /etc/default/earlyoom
+		sudo systemctl enable earlyoom
+		sudo systemctl restart earlyoom
+	fi
+}
+
 # System packages: Debian/Ubuntu only. Skipped where apt-get is absent (e.g. macOS).
 if command -v apt-get >/dev/null 2>&1; then
 	sudo apt-get update
@@ -161,6 +242,9 @@ if command -v apt-get >/dev/null 2>&1; then
 
 	# Low-disk login warning (system-wide profile.d snippet).
 	install_disk_warning
+
+	# On-demand NAS mount helper (cloudpex/).
+	install_cloudpex
 else
 	echo "apt-get not found — skipping system packages (install vim/git manually)."
 fi
@@ -219,6 +303,13 @@ chmod +x "$HOME"/.local/bin/dt "$HOME"/.local/bin/dtach-router "$HOME"/.local/bi
 # Remove any stale dtach wiring from ~/.profile (the menu now ships in ~/.bashrc; see above).
 unwire_dtach_profile
 
+# Optional system changes, offered last so the base install is complete even when
+# declined. Linux/systemd only. Each prompts [y/N] on a terminal, is skipped otherwise.
+if command -v apt-get >/dev/null 2>&1; then
+	offer_tmp_on_disk
+	offer_ssh_memory_guard
+fi
+
 echo "Done. Restart your shell or run: source ~/.bashrc"
 echo "If you use zsh, switch to bash to enjoy these settings =)"
 echo "Note: the deployed bashrc puts ~/.local/bin on PATH — re-login or run: source ~/.bashrc"