I create screen session with
ssh user1@host1, user2@host1, ..., user5@host1. On hardline I see only host1 five times. The same when I press Ctrl+A".
How can I define a hardline to get user1@host1, ..., user5@host1 on it?
Have you already had a look at your ~/.screenrc? This file defines what screen writes to your status lines. Thus, in your current configuration you'll probably find something like that:
hardstatus alwayslastline "[...]%H[...]" which displays the host name in your hardstatus line (see STRING ESCAPES of the man page). To also display the user name replace the line in your configuration with something like:
hardstatus alwayslastline "[...]$USER@%H[...]" you can also have a look at my configuration.