Note that it is fine to enable the repo by editing that line in the repo file, but be sure you disable it again when you are done using the repo. If crucial packages like C libraries get downloaded from a third party repo, you can end up with compatibility issues. And there's really no reason to edit the repo file when you only want one specific package.

It still says bash: john: command not found... when I ran yum install john --enablerepo=dag the last message was Public key for john-1.7.9-1.el7.rf.x86_64.rpm is not installed

Whoops, forgot the public key! Fixed.

Still same error :/

Sorry if I wasn't clear; the missing GPG key prevented the package from installing correctly, so you need to run sudo yum install john again. Or do you mean the "Public key not installed" error showed up again?

Yes I did run sudo yum install john and still "Public key not installed" error showed up again

It also says warning: /var/cache/yum/x86_64/7/dag/packages/john-1.7.9-1.el7.rf.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 6b8d79e6: NOKEY

Sorry for the extra work. All you need to do is edit /etc/pki/rpm-gpg/RPM-GPG-KEY.dag.txt and change the gpgcheck value to 0.

I have the dag repo configured on my machine, but never installed the john package. I found it was there using yum info john --enablerepo=dag, but I didn't actually install it to check that it worked. So now I've done that on a virtual machine, and it DOES work with GPG check disabled.

Actually, you can disable gpgcheck on a per command basis, just like enabling a repo on a per command basis:

So use sudo yum install john --enablerepo=dag --nogpgcheck

And I've just verified with my virtual machine that this actually works. Can you let me know if it works for you?

Hi!

:)

wow that was surprisingly difficult

I also had to do these instructions before I could get john to work :) unix.stackexchange.com/questions/77748/…

Thanks for your help!

You're welcome! I'm impressed with your reputation and history here; glad I could help! :)

I've edited my answer to take the missing key into account; would you mind clicking the check mark to accept the answer?

Sure.

Is installing things on linux this difficult or is it just because this is not a very common program?

No, it's just because I haven't had to do much messing with repos myself. I've had basic Linux sysadmin training but haven't had much on-the-job experience with it yet.

what exactly does mean "repo"?

Repo means "repository", as in "a place where things or resources are stored." Specifically referring to a place where software resources are stored.

so a repo does not necessarily only store uncompiled source code?

Now that you have the config file for the dag repository, in the future, if there's a package you want to install that doesn't show up in the default repos, you can just do yum search packagename --enablerepo=dag.

That's right. It stores software packages along with source code.

oh ok thanks

A good starting point for learning Linux is edx.org/course/introduction-linux-linuxfoundationx-lfs101x-2

That's the first course I did. Nice broad overview.

For the command line specifically, there is a great walkthrough, very long but very very easy going and gradual, here: linuxcommand.org/tlcl.php

Good night! :)

Yes good night! :)