A node at home

Any Linux machine you can reach over SSH can be the node host: a server at home, or one at a provider casty has no script for. Step 0 then creates nothing and only checks the machine.

./scripts/0-provision.sh --host you@192.168.1.20
./scripts/1-node.sh
./scripts/2-client.sh

What the machine needs

Snapchain asks for 16 GB RAM, 4 vCPU, 2 TB of free disk and a public IP. Step 0 and step 1 check the machine over SSH and stop with exit code 5 when it falls short:

• at least 15 GiB of RAM;
• 1.8 TiB free where the database will live. CASTY_MIN_FREE_GIB=1700 before the command asks for less instead, at your risk: once the database fills the disk, the node stops;
• a Docker server the SSH user can talk to, so the user must be root or in the docker group;
• a clock within 60 seconds of yours. Nodes reject messages timestamped more than 15 minutes in the future, so keep NTP running on the host.

A rented server gets Docker, chrony and a higher open-file limit from cloud-init. On your own machine those are up to you.

SSH

casty logs in with your key and never with a password: it runs SSH with BatchMode=yes. The key is ~/.ssh/id_ed25519 unless you pass --ssh-pubkey, and the private half sits next to the public one. The first connection accepts the host’s key and records it; later connections check it.

Where the data goes

The node lives in ~/snapchain of the SSH user, and the free-space check measures the filesystem of that user’s home directory. To keep the database on another disk, mount it, make ~/snapchain a link to a directory on it, and set NODE_DATA_DIR in node.env to the mount point, so the check measures that disk instead.

Ports and firewall

casty creates no firewall for a machine it did not rent. Other nodes reach yours on 3382/udp, the only gossip port Snapchain’s compose file publishes, so forward that from your router. Keep 3381 (HTTP API) and 3383 (gRPC) closed to the internet: casty reaches them through the SSH tunnel. Snapchain’s compose file publishes statsd on 8125/udp and 8126/tcp on every interface unless told otherwise; 1-node.sh sets STATSD_PUBLISH and STATSD_ADMIN_PUBLISH in its .env to the loopback on any host it runs on, this one included, so statsd and Grafana answer on 127.0.0.1 only.

Deleting

0-provision.sh --destroy does not apply here, since nothing was created. ./scripts/1-node.sh down stops the node; the database stays in ~/snapchain until you delete it.