ssh-agent
systemd

$ mkdir -p ~/.config/systemd/user
~/.config/systemd/user/ssh-agent.service
[Unit]
Description=SSH key agent
[Service]
Type=simple
Environment=SSH_AUTH_SOCK=%t/ssh-agent.socket
ExecStart=/usr/bin/ssh-agent -D -a $SSH_AUTH_SOCK
[Install]
WantedBy=default.target

%t $XDG_RUNTIME_DIR

$ systemctl --user daemon-reload
ssh-agent
$ systemctl --user enable --now ssh-agent

export SSH_AUTH_SOCK="${XDG_RUNTIME_DIR}/ssh-agent.socket"

$ ssh-add

ssh-agentsystemd https://abelog.tech/archives/120

.bash_profile ()
if [ -z "$SSH_AUTH_SOCK" -a -x /usr/bin/ssh-agent ]
then
eval `/usr/bin/ssh-agent`
fi