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Old 10-24-2003, 07:02 AM   #1
Registered: Sep 2002
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What are Session ID, Group ID, Process ID...

I was studying daemon processes and i just got tangled in the Session ID, Group ID, Process ID, Parent ID....

Can anyone guide me to a tutorial which explains these IDs and there relation to each other.
Old 10-24-2003, 10:08 AM   #2
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I think it's more important to learn how the deamons handle these IDs than the IDs themselves.
I have read that all linux processes have IDs
And also the deamon may need all these IDs to start a process in an environnement
Old 10-24-2003, 01:05 PM   #3
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Each process has its own ID number. That's how they are identified. If you run 'top', that's PID in the first column. A process can have a parent process - a process it was started from. The parent process usually waits for the children process to finish. Parent process is also PID.

Group ID you mean is, I guess, connected to user names. In fact, the usernames doesn't matter. Every user name has a number (user ID, UID) asociated with it. Every group has an ID, too (group ID,GID). File owners are identified using numbers, not names. So if you delete an user and then create new with the same name, new user won't have access to files owned by the old user (it may happen that the new user will get the same UID as the old user, but it's rare).
Old 10-24-2003, 01:09 PM   #4
Kurt M. Weber
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You can set the UID of the new user explicitly, though.
Old 10-26-2003, 10:33 PM   #5
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Well this is what i know:

There are sessions in linux with a session ID. Each session can have multiple groups with group ID. Each group in turn can have multiple processes with their own precess IDs.

You can create a new session and make your process the session leader by calling 'setsid()' function from within yr application. Your process becomes the leader of this session.

I know all this but still there were some confusions so i wanted to know a some material that tells about all this in detail with maybe some examples.


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