The following will extract the public key from a private key. This assumes your private key is call id_rsa and public key is called id_rsa.pub. This can also be used to validate a public/private key are a match.
ssh-keygen -y -f .ssh/id_rsa
This should match the output of the following:
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".
The method below can be used to convert any accent characters to "?" in a text file. This method can be used to strip accent characters from a subtitle file. The purpose for this is some muxing programs such as dvdauthor will error out when finding these characters.
The method below just converts them to "?". But you can write the results out to a different file then diff against the original to figure out where the characters are then manually convert them if you like.
This will copy a file system from the "/source/dir" to the "/destination/dir".
Note: The source directory can also be / and it will copy correctly.
cd /source/dir tar -cf - . | ( cd /destination/dir ; tar -xpvf - )