To make an SSH connection to a Fuchsia device, some ffx commands
(such as ffx target show and ffx log)
require Fuchsia-specific SSH keys to be present on the host machine.
Concepts
During development, one or more public SSH keys
(listed in fuchsia_authorized_keys) are loaded to a Fuchsia device,
typically when a new Fuchsia image is flashed to the device.
Once the device is loaded with these public SSH keys, the ffx commands
(running from the host machine where a matching private SSH key is stored)
can establish an SSH connection to the device.
Commands that initialize the Fuchsia device, such as ffx target flash
and ffx emu start will generate ssh keys if they are not found.
The location for the ssh key files is configured using ffx config set ssh.pub
and ffx config set ssh.priv.
By default, Fuchsia-specific SSH keys are stored in the
$HOME/.ssh directory of the host machine, as shown below:
$HOME/.ssh/fuchsia_ed25519
$HOME/.ssh/fuchsia_authorized_keys
You can check the configuatrion and consistencty of the ssh keys by running
ffx config check-ssh-keys which will also generate the keys if they are missing,
or update the public key file to include the public key matching the private key
if missing.
These files contain the following:
fuchsia_ed25519: A private SSH key. The content of this file must not be revealed or shared.fuchsia_authorized_keys: A list of one or more authorized public SSH keys.
The fuchsia_authorized_keys file must include the public SSH key for
fuchsia_ed25519. During the flashing process, the fuchsia_authorized_keys
file gets uploaded from the host machine to the Fuchsia device.
If you have multiple development machines, it's recommended that the Fuchsia SSH keys are synchronized across your development machines. This may require you to copy the existing Fuchsia SSH keys files from one machine to another.