A question about user level

thomas2004ch · 01-25-2010, 03:23 AM

I login first with user1, and then log into user3 with 'su', and then to user2 and so on. I can use 'who' to know who is the first user. And using 'whoami' to know who is the current user. But how can I know the user level? Because sometimes I want to change back to the former user by using 'exit', not again using 'su'.

vinaytp · 01-25-2010, 03:55 AM

Hi thomas2004ch...

what do you mean by user levels ? If you are lookig for user logins, here are few points...

Using su, I don't know how to see the user logins

Code:

[vinay@vinay ~]$ who
vinay    tty7         2010-01-25 10:06 (:0)
vinay    pts/0        2010-01-25 10:06 (:0.0)
vinay    pts/1        2010-01-25 10:31 (:0.0)
vinay    pts/3        2010-01-25 14:06 (:0.0)
[vinay@vinay ~]$ su -l vijay
Password: 
[vijay@vinay ~]$ su -l gaurav
Password: 
[gaurav@vinay ~]$ who
vinay    tty7         2010-01-25 10:06 (:0)
vinay    pts/0        2010-01-25 10:06 (:0.0)
vinay    pts/1        2010-01-25 10:31 (:0.0)
vinay    pts/3        2010-01-25 14:06 (:0.0)
[gaurav@vinay ~]$

Above in the output of who command, I can't find vijay and gaurav logins

But your goal can be achieved by ssh login

Code:

[vinay@vinay ~]$ ssh vijay@localhost
vijay@localhost's password: 
[vijay@vinay ~]$ ssh gaurav@localhost
gaurav@localhost's password: 
[gaurav@vinay ~]$ who
vinay    tty7         2010-01-25 10:06 (:0)
vinay    pts/0        2010-01-25 10:06 (:0.0)
vinay    pts/1        2010-01-25 10:31 (:0.0)
vijay    pts/2        2010-01-25 15:23 (localhost.localdomain)
vinay    pts/3        2010-01-25 14:06 (:0.0)
gaurav   pts/4        2010-01-25 15:23 (localhost.localdomain)
[gaurav@vinay ~]$

jschiwal · 01-25-2010, 04:05 AM

I don't know what you mean by user level. You can run "pstree -u" to clearly see a tree of child and parent processes including the user.

Code:

pstree -u | grep -B2 -A4 bob
     |-knotify4
     |-knotify4(jschiwal)---4*[{knotify4}]
     |-konsole(jschiwal)-+-bash---su(root)---bash(bob)-+-grep
     |                   |                             `-pstree
     |                   |-bash
     |                   `-{konsole}

The "who" and "w" programs show logins. The user you su'ed to didn't log in.

thomas2004ch · 01-25-2010, 04:34 AM

Quote:

Originally Posted by vinaytp

Hi thomas2004ch...

what do you mean by user levels ? If you are lookig for user logins, here are few points...

You understand right. What "user level" I mean is the user logins. From your writing I understood that using 'su' one can't see the user logins but using 'ssh', right?

vinaytp · 01-25-2010, 05:51 AM

Quote:

Originally Posted by thomas2004ch

You understand right. What "user level" I mean is the user logins. From your writing I understood that using 'su' one can't see the user logins but using 'ssh', right?

Yes Thomas2004ch,

If you come to kno, please let us kno...

jschiwal · 01-25-2010, 06:20 AM

SU'ing to a user, you are still the person who logged in. There is a UID and an EUID. Using su, your EUID (effective user ID changes). If the real person you su'ed to is logged in, w and who will show that login as well as others.

Using su is logged in /var/log/messages. Using sudo is better because every command is logged.