su another user

[juno2]

I want to let a user A to use "su" to login to another user - user B where user A is null password, i tried to modify the file /etc/group and add user A to the wheel statement , but it still can't run su to login as user B , what is wrong in my system ? thx

[Wouter Jagers]

If both accounts are set up properly, in other words you can use them separately without problems, it shouldn't be too hard.

Can you switch from userA to root ? (using su -)

The command you use as userA is "su - userB" (without the quotes), right ?

regards
Wouter

[Stuart Browne]

Erm, so 'userA' is issuing 'su - userB', and what's the net result? UserA should be prompted for userB's password.

You shouldn't have to worry about 'groups' at all.

The only limitation could possibly be trying to 'su' to 'root' (as you can limit this to a given group or specific users).

Do you get any error's showing up in the log files?

[Steven E. Protter]

Please post the command you are using and the resultant output.

Also publish the log output.

/var/log/lastlog should contain useful information.

SEP

[juno2]

Thx all reply,

Another question, the below is one of the statement on the /etc/shadow file ,

# vi /etc/shadow
User_B:!!:12251:0:99999:7:::

what is the meaning of the password field "!!" ? is it null password ? thx

[Stuart Browne]

No. It's a "No password can match". user cannot log-in.

[Nat Guyton]

You should be able to set an empty password for user B, and anyone can su to that account with no password challenge.

You don't really want to do that, from a security perspective, though.

To allow just user A to su to user B with no password, look at using "sudo" - http://www.sudo.ws/sudo/

If you want user A to run commands as user B and don't want to use sudo, you can use a .rhosts file with rsh (yuck!) or look at ssh with no passphrase in rsa public/private key files...