Start program

Enter the name and parameters of an X client you want to start and display on the X server. For example, to run xeyes

xeyes -fg red

Start program on this computer

Start the chosen or entered program (with parameters as required) on the local machine.

Start program on remote computer

As above but the program will be run on a remote machine.

Using SSH

An X client program can be started remotely via SSH.

There is no mechanism to save a ssh password for security reasons.

SSH X11 forwarding must be enabled in the sshd daemon's sshd_config file on the remote machine, e.g.

X11Forwarding yes

Prompt for ssh password/passphrase

ssh is run within a terminal, allowing the password or passphrase to be entered interactively.

Use keychain to contact ssh-agent

From bash you can start a ssh-agent daemon using keychain (which saves the ssh-agent environment variables to ~/.keychain/${HOSTNAME}-sh, so that subsequent non-interactive shells, such as used by xlaunch can source the file and make passwordless ssh connections).

e.g. to start ssh-agent and load the key ~/.ssh/ida_rsa into it:

$ keychain id_rsa

You will be prompted for the key's passphrase.

Subsequently, xlaunch can run ssh using this key to authenticate without prompting for the passphrase.

When finished, use keychain to stop ssh-agent

$ keychain -k all

See man keychain for more details.

Additional parameters for ssh

Enter any other command line parameters needed by you for the ssh, for example -C to enable compression. ssh compression may improve performance on a slow, low-bandwidth connection, but will slow things down on fast, high-bandwidth networks.

If unsure enter nothing.

Password-less public key authentication

If neither of the options above are selected, you must arrange for ssh to be able to non-interactively authenticate with the remote sshd i.e. install on the remote machine a public key corresponding to a local private key which has no passphrase.

e.g. Create a passphrase-less key-pair, using

ssh-keygen -f ~/.ssh/example-key -N ''

append the public key to your ~/.ssh/authorized_keys file on the remote machine,

ssh-copy-id -i ~/.ssh/example-key.pub user@server

and instruct the local ssh to use the corresponding private key, by adding to ~/.ssh/config (possibly under an appropriate Host section)

IdentityFile ~/.ssh/example-key

See the "AUTHORIZED KEYS FILE FORMAT" section of man sshd and the "IdentityFile" section of man ssh_config for more details.

Troubleshooting SSH

The command run automatically after the X server has started is

ssh -Y <user@computer> <program>

Try this by hand, from a shell, if you have problems.

Using rsh

An X client program can be started remotely via rsh.

You must configure rsh for password-less authentication.