overthinkos/sshd

sshd -- OpenSSH server

Layer Properties

| Property | Value | |----------|-------| | Ports | 22 | | Install files | layer.yml |

Packages

• openssh-server (RPM / deb) — SSH daemon
• openssh-clients (RPM) / openssh-client (deb, singular) — SSH client tools (ssh, scp, sftp)
• openssh (pac) — Arch metapackage bundling both daemon and client
• sudo (rpm / pac / deb) — required for the NOPASSWD rule this layer writes

Cross-distro coverage

rpm: (Fedora), pac: (Arch), deb: (Debian/Ubuntu) — full parity across all four supported package-format families. The openssh-server / openssh-clients naming differs per distro; package-existence tests use package_map: to resolve (see below).

Cross-distro package-test pattern: the sshd layer's openssh-server-package check uses package_map: to resolve the right name per distro — openssh-server on Fedora/Debian, openssh on Arch. This is the canonical worked example for the package_map feature; see /ov:test "Cross-distro package names (package_map:)" for the mechanics and the priority ordering (fedora:43 > fedora when both match).

- id: openssh-server-package
  package: openssh-server        # default
  package_map:
    archlinux: openssh
    fedora: openssh-server
    fedora:43: openssh-server
    debian: openssh-server
    ubuntu: openssh-server
  installed: true

Cross-distro sudoers via getent passwd 1000

The sudoers drop-in at /etc/sudoers.d/ov-user targets the actual uid-1000 account, whatever it happens to be named on the running base image. The layer no longer hardcodes a literal user — instead it discovers the account name at build time via getent passwd 1000:

tasks:
  - cmd: |
      account=$(getent passwd 1000 | cut -d: -f1)
      if [ -z "$account" ]; then
        echo "sshd layer: no uid-1000 account found — refusing to write sudoers" >&2
        exit 1
      fi
      printf '%s ALL=(ALL) NOPASSWD: ALL\n' "$account" > /etc/sudoers.d/ov-user
      chmod 0440 /etc/sudoers.d/ov-user
    user: root

This works uniformly across both user-policy modes:

| Image | Resolved account | Sudoers content | |---|---|---| | fedora-coder, arch-coder, debian-coder | user (create mode — /ov:image "user_policy") | user ALL=(ALL) NOPASSWD: ALL | | ubuntu-coder | ubuntu (adopt mode — /ov-images:ubuntu base_user:) | ubuntu ALL=(ALL) NOPASSWD: ALL |

Why not ${USER} substitution? The generator substitutes ${USER} in task fields (paths, URLs, etc.) but not inside cmd: command text — cmd: is passed verbatim to bash, and bash at RUN time doesn't have $USER exported. getent is the robust, fully-generic alternative. See /ov:layer "${VAR} substitution scope" and /ov:image "user_policy" for the full architectural context.

Usage

# image.yml -- typically used via bootc-base composition
my-image:
  layers:
    - sshd

Used In Images

• Part of the bootc-base composition layer (used in bootc images)
• /ov-images:aurora (disabled)
• /ov-images:selkies-desktop-bootc (via bootc-base) — worked example exercising the dual-mode sudo test below

Testing Notes

• /etc/sudoers.d/ov-user (the NOPASSWD rule written by this layer) is root:root 0750 — the non-root test user (uid 1000 in containers) cannot traverse /etc/sudoers.d/. A file: /etc/sudoers.d/ov-user; exists: true test reports "missing" even when the file is present. Use command: sudo -n -l; stdout: [{contains: NOPASSWD}] to verify the semantic instead. See /ov:test Authoring Gotcha #10.
• Host-side port reachability uses 127.0.0.1:${HOST_PORT:2222}, not ${CONTAINER_IP}:${HOST_PORT:2222}. See /ov:test Gotcha #1.

Dual-mode sudo check — the runuser -u user -- wrapper

ov image test runs with USER=1000 on container images but USER=0 on bootc images (bootc intentionally keeps USER=root because systemd manages user sessions via login). A naïve sudo -n -l; contains: NOPASSWD check fails on bootc — running as root prints root's Defaults block, which doesn't contain the literal string NOPASSWD. The layer's current test drops to user explicitly when running as root:

- id: sudoers-ov-user
  command: |
    if [ "$(id -u)" = "0" ]; then
      runuser -u user -- sudo -n -l
    else
      sudo -n -l
    fi
  exit_status: 0
  stdout:
    - contains: "NOPASSWD"

Portability note: use runuser -u user -- <cmd>, not runuser -l user -s /bin/bash -c '<cmd>'. On Arch util-linux (2.42+), the -l … -c form swallows the wrapped command's stdout — reproduced cleanly: runuser -l user -s /bin/bash -c 'sudo -n -l' prints nothing and exits 0, while runuser -u user -- sudo -n -l prints the full NOPASSWD listing. The layer was fixed to -u … -- after this was caught during arch-ov bring-up. See /ov:test Authoring Gotcha #11.

Related Skills

• /ov-layers:bootc-base -- composition that includes this layer
• /ov-layers:bootc-config -- the bootc boot wiring (tty1 autologin + systemd-user supervisord) that typically runs alongside this layer
• /ov-layers:cloud-init -- depends on sshd for VM provisioning
• /ov-images:selkies-desktop-bootc -- canonical bootc worked example that exercises the dual-mode sudo test
• /ov-images:ubuntu-coder -- canonical adopt-mode example; sudoers correctly targets ubuntu via getent
• /ov-images:debian-coder -- canonical create-mode deb-family example; sudoers targets user
• /ov-images:ubuntu -- declares the base_user: block that makes ubuntu-coder run as ubuntu
• /ov:test -- declarative testing framework (gotchas #10 and #11, package_map:, exclude_distros:)
• /ov:image -- user_policy: field (create / adopt / auto) that drives which account this layer's sudoers targets
• /ov:layer -- layer authoring (${VAR} substitution scope, cmd: vs write:)

When to Use This Skill

Use when the user asks about:

• SSH server setup in containers or VMs
• Port 22 configuration
• OpenSSH server/client packages
• Remote access to bootc images