Arch Linux with LUKS and btrfs on a Hetzner server
A small Python CLI (hal) that wraps every step of installing, encrypting, and
maintaining an Arch Linux server on
Hetzner Dedicated hardware with software RAID,
LUKS full-disk encryption,
btrfs on top of LVM, and remote unlock
via dropbear
in the initramfs.
Author: Kevin Veen-Birkenbach <kevin@veen.world> — veen.world
License: MIT — see LICENSE
Install the CLI
make install # → pip install --user -e .
hal --help
After install, every step below is a single hal subcommand.
Subcommand reference
Run hal --help, hal <group> --help, or hal <group> <target> --help for the live reference.
Top-level
| Command | What it does |
|---|---|
hal status <host> |
Ping + port scan + SSH banner. No login. |
hal diagnose <host> |
Rescue → chroot, runs a fixed inspection script. Pipe with tee to save. |
hal unlock <host> |
Send the LUKS passphrase from the keyring to dropbear (cryptroot-unlock). |
hal forget <host> |
Clear the cached LUKS passphrase from libsecret. |
hal connect <target> <host> [cmd]
Open a shell, or run cmd non-interactively.
| Target | Where it goes |
|---|---|
rescue |
Hetzner Rescue OS |
server |
Booted Arch system |
chroot |
Rescue → chroot of installed Arch (LUKS-unlocks + mounts first) |
hal setup <target> <host> — one-time install operations
| Target | What it does |
|---|---|
image --autosetup PATH |
In rescue: upload autosetup, run installimage. Destructive. |
dropbear |
Booted Arch: install dropbear + mkinitcpio plugins, copy authorized_keys, patch HOOKS. |
grub |
Rescue → chroot: install grub package, write LUKS-aware /etc/default/grub, grub-install on every boot disk. |
encrypt-root |
Rescue: LUKS-encrypt /dev/md1, preserve data via /oldroot copy. Destructive on /dev/md1. Confirms before format. |
hal fix <target> <host> — recovery + maintenance operations
| Target | What it does |
|---|---|
boot |
Patch PermitRootLogin, enable persistent journald. |
network |
Rewrite .network files to match by MACAddress= instead of interface name. |
grub |
Refresh Stage1 + core.img in MBR (Arch doesn't do this automatically after grub upgrades). |
kernel |
Roll the linux package back to the previous version (cache or archive.archlinux.org). |
static-ip |
Replace ip=dhcp in /etc/default/grub with a static cmdline IP derived from /etc/systemd/network/*.network. |
upgrade |
Full pacman -Syyu + initramfs rebuild + grub-install on every boot disk. |
expand-fs |
On booted Arch: lvresize -l +100%FREE /dev/vg0/root && btrfs filesystem resize max /. |
The LUKS passphrase is prompted (hidden) on first use and cached in the libsecret keyring per host — subsequent runs against the same host don't prompt.
Setup flow
Each section is a small handful of hal commands. Click into the corresponding
table row above for what each one actually does.
Set the server IP/hostname once per shell — every block below uses $SERVER:
export SERVER=your_server_ip # e.g. 46.4.224.77 or boot.echoserver
1. Install Arch via installimage
hal connect rescue "$SERVER" # verify rescue is up
hal setup image "$SERVER" --autosetup autosetup # see autosetup.example
hal connect rescue "$SERVER" reboot
Tip: copy autosetup.example to autosetup, edit DRIVE1/DRIVE2/HOSTNAME,
then run setup image.
2. Boot Arch, install the dropbear stack
hal connect server "$SERVER" # verify SSH works
hal connect server "$SERVER" pacman -Syyu # bring system current
hal setup dropbear "$SERVER" # dropbear + mkinitcpio plugins + HOOKS
3. Convert root to LUKS
Activate Rescue in the Hetzner Robot UI, then:
hal connect server "$SERVER" reboot # boots back into rescue
hal connect rescue "$SERVER" # verify rescue is up
hal setup encrypt-root "$SERVER" # LUKS conversion — DESTRUCTIVE
hal setup grub "$SERVER" # initial GRUB for LUKS boot
hal fix static-ip "$SERVER" # static initramfs IP — Hetzner DHCP is fragile
Deactivate Rescue in the Hetzner Robot UI, then:
hal connect rescue "$SERVER" reboot # final reboot into encrypted system
4. Day-to-day use
After every reboot the system blocks at dropbear in initramfs waiting for the LUKS passphrase. From your client:
hal status "$SERVER" # wait for dropbear / sshd
hal unlock "$SERVER" # send passphrase to dropbear
hal connect server "$SERVER" # normal SSH after unlock
5. Expand the root filesystem later
If the autosetup gave you a small root LV and the rest is free LVM space:
hal fix expand-fs "$SERVER"
Debugging an unresponsive server
The server isn't booting / SSH never comes up:
# 1. Reach the server's chroot
hal connect rescue "$SERVER" # via Hetzner Robot → Rescue first
hal diagnose "$SERVER" | tee "diag-$(date +%F-%H%M).log"
# 2. Apply best-guess fixes in roughly this order
hal fix boot "$SERVER" # sshd config + journald
hal fix network "$SERVER" # interface naming drift
hal fix grub "$SERVER" # stale MBR after grub upgrades
hal fix static-ip "$SERVER" # DHCP-in-initramfs fragility
# 3. Last-resort kernel rollback (if a kernel bump is the suspect)
hal fix kernel "$SERVER"
# 4. Or, after fixing whatever was broken, upgrade everything cleanly
hal fix upgrade "$SERVER"
Every hal chroot command makes its own backups (<file>.hal-backup)
before mutating anything, so individual fixes can be reverted by hand.
Sources
- http://daemons-point.com/blog/2019/10/20/hetzner-verschluesselt/
- https://www.howtoforge.com/using-the-btrfs-filesystem-with-raid1-with-ubuntu-12.10-on-a-hetzner-server
- https://code.trafficking.agency/arch-linux-remote-unlock-root-volume-with-mdraid-and-dmcrypt.html
- https://wiki.archlinux.org/index.php/Dm-crypt/Specialties#Remote_unlocking_(hooks:_netconf,_dropbear,_tinyssh,_ppp)
- https://gist.github.com/pezz/5310082