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How can passwordless sudo access be setup on either RHEL (Fedora, CentOS, etc) or Ubuntu distributions? (If it's the same across distros, that's even better!)

Setting: personal and/or lab/training equipment with no concern for unauthorized access (ie, the devices are on non-public networks, and any/all users are fully trusted, and the contents of the devices are "plain-vanilla").

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4 Answers

up vote 33 down vote accepted

EDIT thanks to medina's comment: According to the man page, you should be able to write

ALL            ALL = (ALL) NOPASSWD: ALL

to allow all users to run all commands without a password.


For reference, I'm leaving my previous answer:

If you add a line of the form

%wheel         ALL = (ALL) NOPASSWD: ALL

to /etc/sudoers (using the visudo command, of course), it will let everyone in the group wheel run any commands without providing a password. So I think the best solution is to put all your users in some group and put a line like that in sudoers - obviously you should replace wheel with the actual group you use.

Alternatively, you can define a user alias,

User_Alias     EVERYONE = user1, user2, user3, ...

and use that:

EVERYONE       ALL = (ALL) NOPASSWD: ALL

although you would have to update /etc/sudoers every time you add or remove a user.

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Doesn't ALL work rather than * to specify all users? See the example in sudoers(5). –  medina Jul 15 '10 at 10:58
    
@medina: so it does, I missed that when I was reading the man page. I'll edit. –  David Z Jul 15 '10 at 17:26
    
under Ubuntu, creating a file under /etc/sudoers.d and put these entries in it then it will stop you having to edit sudoers –  Xetius Oct 28 '12 at 20:18
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I tried all the answers on this page, with no useful results. Eventually I figured it out, use this command to list your sudo rights:

sudo -l

This should give you an output like this:

User gmurphy may run the following commands on this host:
    (root) NOPASSWD: ALL
    (ALL) ALL

It shows that I'm configured with root privileges but that I'm still part of a group (admin) matched to a sudo rule which expects the password ("(ALL) ALL"). This was forcing sudo to prompt me. The rule in question was the admin users:

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

Once I commented this out, I was able to sudo without password. I hope this is of use to someone else.

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Ahhh, thanks! This was driving me nuts... in my case, my user was part of the "sudo" group as well as "admin" (which I created), and the permissions on each were mis-matched, as they were in your case. Now this stuff works! :) –  neezer May 6 '12 at 22:28
3  
Commenting a line out is a blunt instrument. You may be interested to hear that "sudo reads the sudoers file and applies permissions in order from top to bottom. So the last line in the file will overwrite any previous conflict" according to ubuntuforums.org/showthread.php?t=1132821 -- and this worked for me. –  David James Jan 15 '13 at 4:08
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Within /etc/sudoers there's an example of just that towards the bottom of the file:

## Same thing without a password
# %wheel        ALL=(ALL)       NOPASSWD: ALL
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that sample wasn't in mine - but thanks! –  warren Oct 1 '12 at 2:39
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There is another way to do it without touching the sudoers file.

  • Edit /etc/pam.d/su and uncomment the line below:

    auth           sufficient      pam_wheel.so trust use_uid
    
  • Add the user to the wheel group.

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