In this lab we are going to make sure we have the minimum knowledge required to successfully pass the RHCE on RHEL8. We’re going to present a scenario that will test an exam candidate’s knowledge of how to use `grep` and configure `ssh` to help students succeed at this exam.
*This course is not approved or sponsored by Red Hat.*
Successfully complete this lab by achieving the following learning objectives:
- Find the Username That the Other Admin Created
There are over 25,000 lines in
/tmp/logfileso we don’t want to do it by hand. While we don’t know the exact format we’re searching for, we’re fairly confident that it’s some form of the word "username".
grep -e 'user.*name' -i /tmp/logfile
That will match any iteration of ‘user’, followed by any character (or no character), followed by ‘name’.
- Create an SSH Key
Use the command
ssh-keygento generate a key that we can use to copy to the
other server to allow passwordless connections.
- Copy the SSH Key to Both cloud_user and the User Whose Name You Discovered in the First Task
ssh-copy-idcommand to copy the SSH key to both the
the new user name:
[cloud_user@Server1 ]# ssh-copy-id cloud_user@<Server2_INTERNAL_IP_ADDRESS> [cloud_user@Server1 ]# ssh-copy-id <USERNAME>@<Server2_INTERNAL_IP_ADDRESS>
Now we can test with two
Back out of that login, and try it for the other user:
Just be sure you’ve substituted the correct
USERNAMEin the commands. We should now be able to perform passwordless
- Ensure That No One Can Use a Password to Log into Server2
Now get out of that shell and come back in as
cloud_user. Once we’ve logged in, we need to edit
/etc/ssh/sshd_configand, with whichever text editor we like best, change the
PasswordAuthenticationvariable to no. We’re using
vias an example here:
[cloud_user@Server2 ]# sudo vi /etc/ssh/sshd_config
Once we’ve done that, restart the SSH daemon using
sudo systemctl restart sshd.
To test, try to log in with a password:
[cloud_user@Server2 ]# ssh -o PreferredAuthentications=password cloud_user@localhost