UNIX for Dummies Questions & Answers

Hello,

As recommended by the moderators I will start my questions here...

I am a little confused by my Linux (CentOS/RHEL) distribution's sudo
mechanism. Or perhaps I just do not know how to use sudo. I can run
a sed command as the root user but it fails to write a root-owned
directory when I run via sudo command.

Is there a config file that sudo uses to determine which commands it
will be managing? Right now I have a sudoers file set this like the
following:

## Allow root to run any commands anywhere
root ALL=(ALL) ALL

## Same thing without a password
%wheel ALL=(ALL) NOPASSWD: ALL

My user is in wheel group.

$ id
uid=500(duderonomy) gid=10(wheel) groups=10(wheel)


Any ideas?

Thanks in advance.
-D

you should probably post the exact commands you're using and any error messages etc... it's really unclear what issue you're having.
are you doing a:
sudo su -
then running some command?

are you running a sudo command line instead? if so what is that command line??

Hi!

I appreciate the feedback that I was vague.
Thank you (very much) for your time.

Here's my input and output for the two cases described in my
original post:

Case A)
---------
$ su -
<entered password>
# cd /etc
# sed -e 's/A/B/' < motd.ORIG > motd
#

It works! (writes file "/etc/motd" which is inside root owned
directory and file also has root ownership)

Case B)
---------
$ cd /etc
$ sudo sed -e 's/A/B/' < motd.ORIG > motd
-bash: ./motd: Permission denied

It Fails.

##

I really need this to work via sudo as this one step
is part of a larger script. I do not see my problem.

Thank you for any hints.

-D

sudo runs the current command as root, but the redirection is handled by your shell before invoking sudo, so that happens as yourself.

A common workaround is to create the file as regular user, then use sudo to copy it to the privileged location. This also reduces the need to run potentially complex commands with elevated privileges.

You are eff'n brilliant! Thank you.

So, if I were to extend what I believe you are saying...

If, for example, I was developing a new root file system for deployment as a new distribution, I work with the files with/in normal user privilege/location. Then, later run sudo on simple commands (such as cp, chown, chmod) to achieve the final desired result.

Thanks,
D

Pretty much, yes. Or create a chroot jail / vmware image / whatever where you will only wreck the thing you're working on if you goof up while playing root.

after you've completely tested, and know exactly what will happen,
you can create a script "with your sed commands, etc in the script"
instead of putting on command line as you were originally.
then you can:

Code:

 sudo "/<path>/script"