Setup ssh agent automatically - janosgyerik/cheatsheets GitHub Wiki

# ssh agent setup

SSH_ENV=$HOME/.ssh/env

start_ssh_agent() {
        ssh-agent > $SSH_ENV
        . $SSH_ENV
}

check_ssh_agent() {
        . $SSH_ENV && test "$SSH_AGENT_PID" && ps -p $SSH_AGENT_PID >/dev/null
}

check_ssh_identity() {
        ssh-add -L >/dev/null
}

add_ssh_identity() {
        ssh-add
}

ssh_agent_setup() {
        check_ssh_agent || start_ssh_agent && check_ssh_identity || add_ssh_identity
}

ssh_agent_setup

• When you login, the script will try to connect to a (previously started) ssh-agent process based on settings saved in ~/.ssh/env
  • If it cannot find an ssh-agent process it will start a new one and save the settings in ~/.ssh/env
• Once the connection with ssh-agent is established, it will check if the agent has any identities stored
  • If not, it will add your default identity (~/.ssh/id_rsa). At this point you will have to enter the passphrase for the identity

As a result, in practice you only have to enter your passphrase once per machine boot. In subsequent bash shells you don't need to enter the passphrase anymore because the ssh-agent already has your identity.