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# Install Arch Linux via SSH

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This article is intended to show users how to install Arch remotely via an SSH connection. Consider this approach when the host is located remotely or you wish to use the copy/paste ability of an SSH client to do the Arch install.

## On the remote (target) machine

Note: These steps require physical access to the machine. If the host is physically located elsewhere, this may need to be coordinated with another person.

Follow the steps from Installation guide#Pre-installation up to and including connecting to the internet (setting the keyboard layout and font can be skipped).

At that point, set the required root password to allow an SSH connection, since the default Arch password for root is empty:

    # passwd

Confirm that `PermitRootLogin yes` is set in `/etc/ssh/sshd_config`. If it is not, set it and reload the OpenSSH daemon `sshd.service` to apply the changes.

Note: If the target machine is behind a NAT router, and you require external access, the SSH port (22 by default) will need to be forwarded to the target machine's LAN IP address. Alternatively, you can setup a reverse SSH tunnel to your local (client) machine and connect back through it, see the `-R` flag of ssh(1).

## On the local machine

On the local machine, connect to the target machine via SSH with the following command:

    $ ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null root@ip.address.of.target

Note: The `-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null` options will prevent verifying and writing the live environment's SSH host keys to `~/.ssh/known_hosts`. This will avoid the `REMOTE HOST IDENTIFICATION HAS CHANGED` warning in case you have ever connected to the IP address before.
Tip: If both machines are on the same local network, you can use the mDNS hostname `archiso.local` in place of the target's IP address:

    $ ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null root@archiso.local

From here one is presented with the live environment's welcome message and is able to administer the target machine as if sitting at the physical keyboard. At this point, if the intent is to simply install Arch from the live media, resume at Installation guide#Update the system clock. If the intent is to edit an existing Linux install that got broken, follow the Install from existing Linux wiki article.

Tip: Consider using GNU Screen or tmux on the target machine (both are available in the live environment), so that if you are disconnected you can reattach to your multiplexer's session.

## Installation on a headless server

This article or section is a candidate for merging with Cloud-init#Archiso.

Notes: The process described here is entirely dependent on cloud-init and is a great illustration of its use, so it should probably be merged and linked from there. (Discuss in Talk:Install Arch Linux via SSH)
Note: These steps may require physical access to the headless machine. Somebody has to insert the installation medium and power up the headless server.

This section describes installation of Arch Linux on a headless server without a keyboard, mouse or display. It uses an additional drive with cloud-init NoCloud configuration to automatically configure OpenSSH authorized keys and optionally iwd connection(s).

### Prepare cloud-init configuration files

There are three required cloud-init configuration files: `meta-data`, `user-data` and `network-config`.

The `meta-data` file can be empty:

    $ printf "" > meta-data

`user-data` will contain the relevant configuration:

    user-data

    #cloud-config
    users:
      - name: root
        ssh_authorized_keys:
          - ssh-ed25519 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
          - ssh-ed25519 YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Replace `ssh-ed25519 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX` with your public SSH key. To add multiple keys, simply repeat the statement as shown above.

To automatically connect to a Wi-Fi network, use the `write_files:` statement to create iwd network configuration files in the correct directory. For example:

    user-data

    #cloud-config
    users:
      - name: root
        ssh_authorized_keys:
          - ssh-ed25519 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
          - ssh-ed25519 YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

    write_files:
    - content: |
        [Security]
        PreSharedKey=aafb192ce2da24d8c7805c956136f45dd612103f086034c402ed266355297295
      path: /var/lib/iwd/spaceship.psk

    runcmd:
    - systemctl restart iwd.service

cloud-init creates network configuration that differs from one shipped in the ISO. I.e. mDNS responder and DHCPv6 client are not enabled. To avoid this, disable cloud-init's network configuration in `network-config`:

    network-config

    version: 2
    config: disabled

Once all three files are created they need to be placed on a drive with an ISO 9660 or FAT volume labeled `CIDATA`.

### Using an additional FAT formatted drive

Use a FAT formatted drive. Copy `meta-data`, `user-data` and `network-config` to the drive and change the file system's LABEL to `CIDATA`.

You will need to attach this drive to the headless machine in addition to the one with the official ISO.

### Using an additional ISO

Create a `cloud-init.iso` file using xorriso from libisoburn:

    $ xorrisofs -output cloud-init.iso -volid CIDATA -joliet -rational-rock meta-data user-data network-config

Prepare the cloud-init data medium by burning `cloud-init.iso` to an optical disc or, if deployment options permit, use the ISO as is.

### Using a single USB flash drive

If the installation image is written to e.g. a USB flash drive, provided there is enough space on the drive, an additional partition to house cloud-init data can be created.

Install dosfstools, mtools and libisoburn.

First create a 2 MiB FAT image with its LABEL set to `CIDATA`:

    $ mkfs.fat -C -n CIDATA cloud-init.img 2048

Copy the `meta-data` and `user-data` files to the root of it:

    $ mcopy -i cloud-init.img meta-data user-data network-config ::

Repack the official ISO to include the FAT image as a third partition:

    $ xorriso -indev archlinux-version-x86_64.iso -outdev archlinux-version-x86_64-with-cidata.iso -append_partition 3 0x0c cloud-init.img -boot_image any replay

Finally follow USB flash installation medium#Using the ISO as is (BIOS and UEFI) to prepare the USB flash drive installation medium using the repacked ISO (`archlinux-version-x86_64-with-cidata.iso`).

### Using a single custom-built ISO

Alternatively, create a custom ISO using Archiso. This allows using only one drive regardless of type.

Use the releng profile as basis. Place the cloud-init configuration files in `airootfs/var/lib/cloud/seed/nocloud/` and build the ISO.

### Boot from the installation medium

Once finished, deploy the installation medium and the cloud-init data medium (if it is separate) to the headless machine using the appropriate method.

Power up the headless machine and boot into a live Arch environment from the installation medium. Wait for a minute or so to allow the headless machine time to boot up and connect to the network.

From your existing machine (with keyboard and display) SSH into the live Arch environment on the headless server and complete the installation as described in the Installation guide.

Note: To belabor the obvious, all the Wi-Fi and SSH configuration that was carried out in the boot image needs to be done again in the actual Arch Linux installation to allow Wi-Fi SSH access to the headless machine after installation.
Categories:

- Installation process
- Secure Shell

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