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I have an strange problem...
I cannot login to my Ubuntu using my own private key. Fortunately I have a password and it works but I cannot change my password. I can su user to root. See the following command outputs:

root@myhost:/# passwd myuser
Enter new UNIX password: 
Retype new UNIX password:
passwd: Authentication token manipulation error
passwd: password unchanged

Then I tried this:

root@myhost:/# pwconv
pwconv: cannot open /etc/passwd

There aren't any .lock files in /etc but 

/etc/group 
/etc/group-
/etc/gshadow
/etc/gshadow-
/etc/shadow
/etc/shadow-
/etc/passwd
/etc/passwd-

are exist.

What can I do?

mahyard
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  • Someone asked the same question some years ago on Ask Ubuntu. https://askubuntu.com/a/57622/67665 Can you check if the accepted solution there applies to you? – pkhamre Jan 31 '18 at 10:47
  • I had checked it before but it did not help me, @pkhamre – mahyard Jan 31 '18 at 11:03
  • So you are saying that an entry for `myuser` exists in both `/etc/passwd` and `/etc/shadow`? `sudo grep myuser /etc/passwd` and `sudo grep myuser /etc/shadow` – pkhamre Jan 31 '18 at 11:18
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    yes, I confirm @pkhamre – mahyard Jan 31 '18 at 11:27

2 Answers2

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This may be related to incorrect permissions set to /usr/bin/passwd. Try to set the permissions to 4755 using the command:

sudo chmod 4755 /usr/bin/passwd

Which means: User can read, write and execute, group and others can read and execute, and set UID bit.

Alisio Meneses
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  • so I have 2 questions: 1st) I didn't changed this before. why this should be happened. changing the default permissions isn't unsafe? 2nd) I cannot change the permissions. this error occurs: `chmod: changing permissions of '/etc/shadow': Operation not permitted` – mahyard Jan 31 '18 at 11:06
  • 1st question) It is unsafe, but 4755 is the default permission, according to my fresh xenial install. 2nd question) You must type 'sudo' before administrative applications. I edited the answer to include the sudo command. – Alisio Meneses Jan 31 '18 at 12:21
  • I'm not so newbie :) if you check the question again you can see that I changed to root user. so there is no need to sudo – mahyard Jan 31 '18 at 12:59
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Maybe something or someone has set an immutable flag for /etc/passwd and/or /etc/shadow file.

Check with lsattr /etc/passwd /etc/shadow and if the result contains i in response, remove the immutable flag with chattr -i /etc/passwd /etc/shadow.

Janne Pikkarainen
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