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I'm using rhel 5, when i'm working in terminal first i typed su command and by mistake i entered copy command and some other characters, after realising i've made a mistake then i came out and continued with copy command in terminal.

after some time when i tried to login by using su and with password it says "incorrect password".

So i logged out and entered root login for gui and it works well, but i'm not able to use the same password for su.

can some one get around this issue?

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migrated from May 6 '11 at 11:06

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Which files where you copying? Does su has the setuid bit? Are you executing the right su (/bin/su) instead of some other location (~/bin/su, for example)? – Carlos Campderrós May 6 '11 at 9:33
@Carlos Campderrós first i tried to login using su, after typing 'su' instead of password i typed copy command ,then realised i mad a mistake and came out of it after that i continued my work. but after some time i again tried to login using su, it says 'incorrect password'. but meanwhile i didn't changed any passwords... – Sekar May 6 '11 at 11:00
up vote 3 down vote accepted

Probably you have locked the root user by too many wrong authentications. Try

usermod -U root

to unlock the account.

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I had the same problem and none of the above replies helped. In my case, I could login as root, sudo worked, but not su.

It turned out that /bin/su had somehow lost the suid permission.

I corrected that with chmod u+s /bin/su, and then su worked again.

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Make sure the user trying to su is in the wheel group.

$ id uid=1000(usr) gid=1000(usr) groups=1000(usr),10(wheel),18(audio),19(cdrom),35(games),442(plugdev),1003(pulse-access)

if you don't see wheel, your su will fail.

Or you can edit the su file in the /etc/pam.d directory and modify it to not require wheel group to be able to escalate your privileges.

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