To remove file in Linux that has a hyphon or dash in front of it just prefix it with "./".  For example:

rm ./-testfile

1. power off the pi, remove the MicroSD card, and put that in a PC.
2. Then in the drive called "boot", create a file named "octopi-password.txt"
3. In that text file ("octopi-password.txt") you only need the password you want to set for the "pi" user, nothing else.  So it will be one word only in this file. 
4. Now take the MicroSD out of the PC, install it in the pi and boot it. 
5. You can now log in again using SSH, with username "pi" and the password you set in the file "octopi-password.txt".

To use journalctl to view the logs of the last reboot use the following:

journalctl --boot=-1

This command is handy for viewing logs right before a crash. Do the above command then use shift-g to go to the bottom of the list.

To find the install history of a specific RPM do the following:

rpm -q  --last

To find the install history of all RPMs do the following:

rpm -qa --last

NOTE: This will not sort them by install date.

Run the following command to connect

openssl s_client -connect {server}:{port} -starttls smtp

Then find out what authentication is supported. It should now show "AUTH LOGIN" now that you have an encrypted connection:

ehlo {domain.com}

If you see "AUTH LOGIN" in the list then do the following:

List all zones:

 firewall-cmd --list-all-zones

List all active zones:

firewall-cmd --get-active-zone

To add a host or network to allow all connections from:

firewall-cmd --permanent --zone=trusted --add-source=10.10.10.10

Add a service to be allowed from anywhere:

firewall-cmd --permanent --add-service=smtp

When you run firewall-cmd with the "--permanent" it will not be active until the dameon is reloaded. Do the following to make them active:

firewall-cmd --reload

Here is a quick way to get the current epoch with the date command:

date +%s

If you find your Fn keys don't work like volume up/down try the following:

su -
echo asus-nb-wmi > /etc/modules-load.d/asus-nb-wmi.conf
reboot

In Fedora, the badblocks program is part of the e2fsprogs program. You probably already have that installed. But in case you don't do the following:

yum install e2fsprogs

To just see the bad blocks the following to do a non-destructive read/write test:

badblocks -nvs /dev/sda

To generate generate a list of the bad blocks do the following:

badblocks -nv /dev/sda > badblocks.txt

Now you can mark the bad blocks found with the following: