Re: Bug or missing feature in who
[EMAIL PROTECTED] (Bob Proulx) writes: Alexander Schestag wrote: So, is there a way to tell who to list the users logged in via su as well? Not with who. AFAIK you would need to walk the process list for that information. There is really nothing special about a login process. It is just a normal process. Actually a login process is kind of special, because it creates a new session and becomes the leader of it. Changing the user with su, on the other hand, does not create a new session (use ps -ej to display the session id of every process). Still, it is the sole responsibility of the process creating the session to update the utmp/wtmp information. In other words, you cannot trust this information in any way. Andreas. -- Andreas Schwab, SuSE Labs, [EMAIL PROTECTED] SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 And now for something completely different. ___ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils
Re: Bug or missing feature in who
Andreas Schwab wrote: [EMAIL PROTECTED] (Bob Proulx) writes: Alexander Schestag wrote: So, is there a way to tell who to list the users logged in via su as well? Not with who. AFAIK you would need to walk the process list for that information. There is really nothing special about a login process. It is just a normal process. Actually a login process is kind of special, because it creates a new session and becomes the leader of it. Changing the user with su, on the other hand, does not create a new session (use ps -ej to display the session id of every process). Still, it is the sole responsibility of the process creating the session to update the utmp/wtmp information. In other words, you cannot trust this information in any way. Not to mention that it's trivially easy to create a new session, and many programs do it as a matter of course (especially dæmons). The create new session syscall is generally used to disassociate from whatever terminal and process group it was running under, so it won't accidentally try to write to the terminal while it's in the background (STOPping it); and won't receive SIGHUP if that terminal goes away. -- Micah J. Cowan Programmer, musician, typesetting enthusiast, gamer... http://micah.cowan.name/ ___ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils
Bug or missing feature in who
Hello, I think, I detected a bug or at least a missing feature in the who command. Assume the following situation: - user1 is logged in. a who will show me this user. - after that, user1 logs in as another user or as root via su. Unfortunately, in this situation, the who command doesn't list the user logged in via su. Is this a bug, a missing feature, or is it a wanted behaviour of who? who /var/log/wtmp/ lists the logged in root user, but it also lists users already logged out. So, is there a way to tell who to list the users logged in via su as well? Best wishes, Alex Schestag -- Alexander Schestag http://www.schestag.info PGP encryption welcome! Key-ID: 0x1F938C08 @ usual places ___ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils
Re: Bug or missing feature in who
Alexander Schestag wrote: I think, I detected a bug or at least a missing feature in the who command. The who command reports information found in the system utmp file. But updating the contents of the utmp file is the responsibility of the operating system. Assume the following situation: - user1 is logged in. a who will show me this user. The /bin/login program, and any replacement such as sshd or the older telnetd, update the contents of the /var/run/utmp file when a user logs into the session. - after that, user1 logs in as another user or as root via su. The su command does not update the utmp file. Running su does not change the name of the user who logged into that session. Unfortunately, in this situation, the who command doesn't list the user logged in via su. Is this a bug, a missing feature, or is it a wanted behaviour of who? It is not a bug. It is expected behavior. The 'su' command stacks another process on top of the first with the new process being the new user. But this does not change who logged into that session. The first user logged into that terminal session and therefore the system utmp file will continue to show the previous user on that session. When you exit the stacked shell you will return to the previous user session. The utmp file is a very old part of unix-like systems. I doubt if today, 30 years later, that it would be implemented the way that it was way back then. Note that the utmp and wtmp files are running totals kept by various system programs. It is not unusual for system events (e.g. disk full, crashed login shells) to cause them to be out of sync with each other. I would not use it for ultimate accuracy. There is very little good use of the utmp file today. Most people using it should probably be using the user name of the current user and not the user that logged into that terminal session. who /var/log/wtmp/ lists the logged in root user, The wtmp file attempts to track logins and logouts. The utmp file attempts to track currently logged in users. but it also lists users already logged out. Correct. So, is there a way to tell who to list the users logged in via su as well? Not with who. AFAIK you would need to walk the process list for that information. There is really nothing special about a login process. It is just a normal process. If I read what you said right it sounds like you are logging in as root and then using su to switch to a user. In which case the logged in user is root and the report is correct. Bob ___ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils
