4/17/16 - Fixed formatting. I wanted to add an SSH key to a new minimal Debian VM install, but attempting to add the key resulted in a No such file or directory error.
sudo cat id_rsa.pub >> .ssh/authorized_keys
cat: id_rsa.pub: No such file or directory
The error was the result of the non-existent authorized_keys file which is where SSH key happens to be stored. If we look inside the ~/.ssh directory you will notice the missing authorized_keys file.
To be able to store the SSH key create the missing authorized_keys in the right location and with the right permission. Move to the directory where key files are stored for the user.
Create necessary file.
Assign permission to file.
chmod 600 authorized_keys
Copy SSH key to authorized_keys file.
cat id_rsa.pub >> .ssh/authorized_keys
Optional, but I recommend removing the key since it’s no longer needed.
Restart the service.
sudo service ssh restart