Dear all,
It is weird when i su - <username> it shows

[root@virtual ~]# su - <username>
-bash: [<username>: command not found
[root@virtual ~]#

I need the explanation to furnish my knowledge

TQ

We need to know your distribution name to furnish your knowledge !

EDIT
As I can see you typed this from root !
What command did you use to log in root ?

I think the explanation is that you are supposed to replace <username> with an actual username, such as root. However, in the example you give, I see the # sign at your prompt, and the name 'root@host' in your prompt, which means (usually) that you are already the root user, and should probably put some other username there instead.

As Anish implied, when asking questions, the more information you provide, the better! At the very very least, it helps to know what Linux you are running, in case the suggestions to help you might vary from one OS to another.

Sasha

[root@icbavirtual ~]# su - oradb
-bash: [oradb: command not found
[oradb@icbavirtual ~]$

Try just su oradb

or sudo -u oradb bash

I can see from your post that you are already logged in as the user oradb. And bash is trying to execute the username as a command here, thats weird.

What is the output of

this is the output

[root@icbavirtual users]# alias su
-bash: alias: su: not found
[root@icbavirtual users]# echo "'$PS1'"
'[\u@\h \W]\$ '
[root@icbavirtual users]# echo "'$PROMPT_COMMAND'"
'echo -ne "\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}\007"'
[root@icbavirtual users]#

Thanks for the information. I don't see any problem there.

Unfortunately I forgot that su could be a function as well an alias What is the output of

Please note that PS1 and PROMPT_COMMAND should be checked for user oradb (not root), since the "switch user" command succeeded and maybe there is something weird after that.

Thanks for spotting that colucix

On re-reading the thread, the symptoms are uncertain. From the first postbut later
Guessing the first was entered manually and the last line is wrong, then the "su -" command does succeed in switching user and the error message most likely comes from oradb's shell initialisation files.

Assuming the login shell is bash, this can be tested, as oradb, by running If the first generates the error message but the second doesn't then the problem is in one of ~/.bash_profile, ~/.bash_login or ~/.profile.