Ubuntu Server Questions

Hi, I'm newly registered to the site although I referenced it several times to transition from Xandros OCE; this site has been quite helpful. I was originally going with Slackware but decided Ubuntu Server would work well for my purposes. I'm like the digital picture archivist for my family so I'm running a home file/print server with ssh enabled. I have SAMBA and SSH working but I haven't set the printer up (CUPS) yet. I think I'm only slightly more than a Linux noob but I decided to go with a command line distro to force myself to learn. My first question is how can I tell which user accounts are for the system and which are created for people to log in to the system? I understand that there are accounts created for the system to do its job and I only want those accounts plus the accounts I have authorized/created. My second question is whether there a way that I can see a record of all logins (successful and attempted) to my system? I read that I can use "last" and lastb" but will this show all logins since the system was created? I saw that there was a limitation to this command but I'm not clear. I know the computer would eventually fill up if it logged and kept every entry so I guess I'm looking for something along the lines of the "history" command but for logins. I'm aware of RTFM and I have tried to read as much as possible but these issues I am uncertain of, regardless of how much reading I do. This is just a personal home server and I have changed the default SSH port but I'll follow up on any other ideas about securing it if you have any. Thanks. Mark

Thanks, I'll check it out.