I'm using fedora19, and I've added wheel to my account like this.

usermod -a -G wheel ironsand

And I've logged out and logged in again to take effect the command according to the following answer. https://ask.fedoraproject.org/question/9769/sofia-is-not-in-the-sudoers-file/

I don't need to restart when I change .bashrc, if I use source command. Is there no way to take usermod effect likewise?

marked as duplicate by Thomas Nyman, terdon, slm, jasonwryan, Joseph R. Oct 16 '13 at 22:23

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  • You don't need to log out to login. Running su <username> is sufficient. – Marco Oct 16 '13 at 17:31

Careful where you draw your analogies. The sourcing of the .bashrc can be dangerous in the sense that if a variable is being added to you'll get into the situation where something like this can occur:

initial env


sourced env


That's why it's generally a good practice to logout and log back in when fundamental changes are made to low level environment files such as .bashrc and/or .bash_profile.

Being added to or removed from Unix groups should also be viewed as a major change, requiring a logout/login.

You can get some access, at least in a single shell, by also doing one of these 3 operations with respect to the Unix group changing showing up:

  • su - <user>
  • su <user>
  • newgrp

The 3rd method will work, but it will require you to blindly change your self to a group that doesn't show up yet in your existing environment, and will then make your primary group this new group, which may not be what you want.


If you take a look at the man page, credentials you'll see why child processes cannot have changes made via usermod immediately reflected in a real-time way:


A child process created by fork(2) inherits copies of its parent's user and groups IDs. During an execve(2), a process's real user and group ID and supplementary group IDs are preserved; the effective and saved set IDs may be changed, as described in execve(2).

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