版主, thank you very much. Sorry I could't type in chinese now.
I inserted the comand you told me, but I don't know its meaning. Could you explain it, OK? 3Q
[flacs@localhost ~]$ man which
[flacs@localhost ~]$ which groupadd
/usr/bin/which: no groupadd in (/usr/kerberos/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/home/flacs/bin)
[flacs@localhost ~]$ echo $PATH
/usr/kerberos/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/home/flacs/bin
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[flacs@localhost ~]$ which groupadd
/usr/bin/which: no groupadd in (/usr/kerberos/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/home/flacs/bin)
[/code:1]
means that you have no groupadd in the PATH which contain the directory searching the command you type, so I think you need to find where "which" command is and reset the variable "PATH" to add the path including your "which" command by adding the following line in your $HOME/.bashrc:
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export PATH=$PATH:/path/to/which
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and then execute
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. ~/.bashrc
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have a try and good luck!