clover's git

the-knife

1	---
2	title: Servers
3	description: Launch Hetzner Cloud Servers with Alchemy — SSH keys and typed SSH access, cloud-init, networks, volumes, snapshots, and placement groups.
4	---
5
6	A [`Server`](/providers/hetzner/server) is a Hetzner Cloud VM: pick
7	a size, an OS image, and a location, and it boots in about ten
8	seconds, billed by the hour. It's both a raw compute primitive and
9	the host that [Services](/hetzner/compute/services) deploy onto.
10
11	## Launch a server
12
13	The minimal server is a type, an image, and a location:
14
15	```typescript
16	const server = yield* Hetzner.Server("box", {
17	serverType: "cx22",
18	image: "ubuntu-24.04",
19	location: "nbg1",
20	});
21	```
22
23	All three are create-only — changing any of them **replaces** the
24	server. The resolved resource exposes `ipv4`, `ipv6`, `serverId`,
25	`status`, and the rest of the observed state — see the
26	[`Server` reference](/providers/hetzner/server).
27
28	To discover what's available, use the catalog helpers — each
29	accepts a name or numeric id and fails with a typed
30	`CatalogNotFound` if it doesn't exist:
31
32	```typescript
33	const serverType = yield* Hetzner.findServerType("cx22");
34	const image = yield* Hetzner.findImage("ubuntu-24.04");
35	const location = yield* Hetzner.findLocation("nbg1");
36	```
37
38	## SSH keys
39
40	Register your public key as an [`SshKey`](/providers/hetzner/sshkey)
41	and inject it at create time:
42
43	```typescript
44	const key = yield* Hetzner.SshKey("laptop", {
45	publicKey: "ssh-ed25519 AAAA... you@laptop",
46	});
47
48	const server = yield* Hetzner.Server("box", {
49	serverType: "cx22",
50	image: "ubuntu-24.04",
51	sshKeys: [key],
52	});
53	```
54
55	Hetzner applies injected keys only when the server is provisioned —
56	changing `sshKeys` later doesn't touch a live server.
57
58	Separately from your keys, Alchemy generates a **deploy key** for
59	every server it creates and injects it at boot. That key (persisted
60	redacted in state) is how [`Hetzner.Ssh`](#run-commands-over-ssh)
61	and [`Hetzner.Service`](/hetzner/compute/services) reach the box
62	with zero SSH configuration on your side.
63
64	## Run commands over SSH
65
66	The `Ssh` binding gives you typed `exec`/`scp` against any managed
67	server, from deploy-time Effects like
68	[Actions](/infrastructure-as-code/action):
69
70	```typescript
71	const ssh = yield* Hetzner.Ssh(server);
72
73	const { stdout } = yield* ssh.exec("uname -a");
74	yield* ssh.scp("./assets.tar.gz", "/opt/app/assets.tar.gz");
75	```
76
77	`exec` returns `{ stdout, stderr, code }` and **fails** with a typed
78	`Hetzner.SshError` on a non-zero exit. `scp` accepts a local path or
79	a `Uint8Array` and creates the remote directory if needed. Both use
80	the server's deploy key and the `root` user by default; pass
81	`{ user, privateKey }` to override.
82
83	## Cloud-init
84
85	`userData` runs on the server's first boot — the place to install
86	packages, write config files, or add users:
87
88	```typescript
89	const server = yield* Hetzner.Server("box", {
90	serverType: "cx22",
91	image: "ubuntu-24.04",
92	userData: `#cloud-config
93	packages:
94	- postgresql
95	`,
96	});
97	```
98
99	A shell script works too, and so does a bare snippet — Alchemy adds the
100	`#!/bin/bash` shebang cloud-init needs to execute one:
101
102	```typescript
103	const server = yield* Hetzner.Server("box", {
104	serverType: "cx22",
105	image: "ubuntu-24.04",
106	userData: `#!/bin/bash
107	apt-get update
108	DEBIAN_FRONTEND=noninteractive apt-get install -y nginx
109	systemctl enable --now nginx
110	`,
111	});
112	```
113
114	Alchemy has its own bootstrap script that pre-installs
115	[Bun](https://bun.sh) for [Services](/hetzner/compute/services). Your
116	`userData` does not replace it: the two are combined into a multipart
117	cloud-init document and both run, Alchemy's first. To take over the
118	whole payload, bootstrap included, pass a document that already starts
119	with a `Content-Type:` header.
120
121	The composed document is capped at 32 KiB (Hetzner's limit) — over that,
122	the deploy fails with `Hetzner.ServerUserDataTooLarge`.
123
124	:::caution
125	Cloud-init only runs once, on first boot, so **changing `userData`
126	replaces the server**. Plan for it the way you would an `image` or
127	`serverType` change: the new server is created, dependents are pointed
128	at it, then the old one is deleted.
129	:::
130
131	## Attach infrastructure
132
133	Networks, firewalls, volumes, and a placement group are all props —
134	each accepts the resource directly (yielded or module-scope) and is
135	kept in sync on update:
136
137	```typescript
138	const server = yield* Hetzner.Server("box", {
139	serverType: "cx22",
140	image: "ubuntu-24.04",
141	networks: [network],
142	firewalls: [firewall],
143	volumes: [volume],
144	placementGroup: group,
145	});
146	```
147
148	See [Networking](/hetzner/networking) for networks, firewalls, and
149	load balancers, and [Volumes](/hetzner/data/volumes) for storage.
150
151	## Placement groups
152
153	A [`PlacementGroup`](/providers/hetzner/placementgroup) of type
154	`spread` guarantees its members run on distinct physical hosts —
155	cheap insurance for redundant pairs:
156
157	```typescript
158	const spread = yield* Hetzner.PlacementGroup("spread", {
159	type: "spread",
160	});
161
162	const a = yield* Hetzner.Server("a", { /* ... */ placementGroup: spread });
163	const b = yield* Hetzner.Server("b", { /* ... */ placementGroup: spread });
164	```
165
166	## Snapshots
167
168	[`Image`](/providers/hetzner/image) captures a server's disk as a
169	snapshot (or converts an existing backup):
170
171	```typescript
172	const golden = yield* Hetzner.Image("golden", {
173	server,
174	type: "snapshot",
175	description: "app image v1",
176	});
177	```
178
179	Boot new servers from it by passing the image to another Server's
180	`image` prop.
181
182	## Where next
183
184	- [Services](/hetzner/compute/services) — deploy code to the server
185	as a supervised systemd unit.
186	- [Volumes](/hetzner/data/volumes) — durable block storage.
187	- [Networking](/hetzner/networking) — private networks, firewalls,
188	load balancers, stable IPs.
189	- [`Server` reference](/providers/hetzner/server) — every prop and
190	attribute.