What does -D -a mean in the output of ps -p <pid> -o command?

Solution 1:

the "-D -a" have nothing to do with PS. PS is listing the processes - and a running process is "/usr/bin/ssh-agent -D -a /run/user/1000/keyring/.ssh" - ie the -D -a are parameters passed to ssh-agent.

With respect to ssh-agent: -D means run in foreground, and -a means "bind to all addresses".

On my Ubuntu system, I see 2 "ssh-agent" processes - one in the background, presumably related to command line stuff I'm doing, while a second one is a client of the desktop session, so likely in the foreground so it can interact with that. (Indeed when I kill the process associated with the one with the -D -a options and do an ssh session from the desktop it asks me to authenticate again, and relaunches that process)