Fedora CoreOS: cirrus edge (production)

Single Fedora CoreOS host that runs only sish, as a rootful Podman quadlet with host networking. Everything is defined in cirrus.yaml (Butane) and applied once at install time by Ignition. The VPS is too small for Talos, so production runs on CoreOS; the Talos setup in talos/ and kubernetes/ stays the dev edge.

File
`cirrus.yaml`	Butane config: users, sshd, firewall, sish, updates
`.secrets/ssh_host_ed25519_key`	Edge SSH host key (gitignored). Connectors pin its public half (`SISH_HOST_KEY`)
`.secrets/connector-cumulus`	Private key of the `cumulus` connector (gitignored), goes into a Secret in `cumulus`
`cirrus.ign`	Build output, embeds the host key (gitignored)

Build and install

butane --strict --files-dir coreos coreos/cirrus.yaml > coreos/cirrus.ign
coreos-installer install /dev/<disk> --ignition-file coreos/cirrus.ign   # or the provider's user-data

Ignition runs only on first boot. Changing cirrus.yaml later does nothing to a running host: either reinstall, or make the same change on the host by hand (and keep the file in sync).

Admin access: ssh -p 5001 core@tunnel.traberph.de (public key only, user core only).

Network

Hostname cirrus.traberph.de. netcup gives IPv4 via DHCP (46.38.234.119) but no IPv6 router advertisements with a usable prefix: the IPv6 address from the netcup panel (/64) is set statically in /etc/NetworkManager/system-connections/ens3.nmconnection, gateway fe80::1.


IPv4	`46.38.234.119` (DHCP)
IPv6	`2a03:4000:2:83c::1/64` (static), gateway `fe80::1`

Only the global address (scope global) goes into DNS, never the fe80:: link-local one.

Ports

nftables (/etc/sysconfig/nftables.conf), default drop. Loopback, ICMP, DHCP replies and replies to outgoing connections are allowed.

Port (tcp)
5001	Admin sshd
5002	sish SSH endpoint for connectors (public key auth)
80	sish HTTP, routed by `Host` header
443	sish TLS passthrough, routed by SNI
22, 20000-20099	Raw TCP forwards (22 = Gitea SSH)

The forward ports must match port-bind-range in the sish config, otherwise a claimed port is silently unreachable.

sshd on 5001 needs an SELinux exception (5001 is labelled commplex_link_port_t): sshd-port-selinux.service installs /etc/cirrus/sshd_port_5001.cil once and again whenever an OS update dropped it.

sish

Path on the host
`/etc/containers/systemd/sish.container`	Quadlet unit (`sish.service`): non-root (uid 65532), only `CAP_NET_BIND_SERVICE`, read-only root, `MemoryMax=256M`. Own writable `/tmp` tmpfs (`Tmpfs=…,mode=1777,notmpcopyup`): sish creates a temp file per forward, and podman's automatic read-only `/tmp` (copied from the image, root 755) would make every forward fail with "remote port forwarding failed"
`/etc/sish/config.yml`	sish config, same as `kubernetes/base/sish/config.yml` except the values below
`/var/lib/sish/keys/`	Host key (read-only in the container)
`/var/lib/sish/pubkeys/clients`	Authorized connector keys, `authorized_keys` format

Differences to the k8s config:


`ssh-address: ":5002"`	2222 in k8s
`domain: tunnel.traberph.de`	The edge's own name. A requested name without a dot becomes `<name>.tunnel.traberph.de`
`bind-any-host: true`	Single tenant: connectors may claim any hostname containing a dot, wildcards included. Replaces `bind-hosts`
`verify-dns: false`	No `_sish` TXT ownership checks (pointless with `bind-any-host`)

Every authorized key can claim every hostname and port, and with the load balancers on it can join an existing one. So only add keys of connectors you control (sish has no per-key permissions).

Add or remove a connector: edit /var/lib/sish/pubkeys/clients on the host (sish watches the directory, no restart needed) and the same block in cirrus.yaml.

Config change: edit /etc/sish/config.yml, systemctl restart sish, mirror it in cirrus.yaml. Connectors drop for a few seconds and reconnect on their own.

systemctl status sish
journalctl -u sish -f

DNS

Record
`tunnel.traberph.de` A/AAAA → VPS	Connectors (:5002) and admin SSH (:5001)
`<host>` or `*.<domain>` A/AAAA → VPS	Every hostname a connector serves; unclaimed names get a 404 (:80) or no answer (:443)
`*.tunnel.traberph.de` A/AAAA → VPS	Optional, only if fallback names should be reachable

A wildcard claim (*.example.com) does not cover the apex example.com, neither in DNS nor in sish: connectors claim the apex separately. Records that point elsewhere (e.g. still proxied through Cloudflare) take precedence over the wildcard; deleting such a record silently moves the name to the edge, where it only works if a connector serves it.

Updates

Both are automatic:

OS: Zincati stages new Fedora CoreOS releases (stable stream) and reboots only in the window 03:00-04:00 UTC (/etc/zincati/config.d/55-updates-strategy.toml).
sish: upstream publishes only exact tags (v2.24.0), so podman auto-update can't follow a version line. sish-update.timer (daily ~05:00 UTC) runs /usr/local/bin/sish-update, which sets Image= in the quadlet to the newest tag matching TRACK=v2. (minor + patch, never a new major), restarts sish and rolls back if nothing listens on :5002 after 30s. TRACK=v2.24. limits it to patch releases.

journalctl -u zincati -u sish-update
systemctl start sish-update   # check now

Both restart sish (tunnels drop for a few seconds). A major sish release (v3) is a manual change of TRACK and Image=.

First boot checklist

ss -tlnp: sish on 22, 80, 443, 5002; sshd on 5001.
journalctl -u sish: Loading ssh_host_ed25519_key as ssh-ed25519 host key (the provisioned key, not a generated one).
After the first OS update: SSH on 5001 still works, semodule -l | grep sshd_port_5001.