Editing RaspberryPi4B (section)

===Backup of Raspberry 3B (Old OS)===
* fetch files from Raspberry 3B and copy it to Google Drive
====Preparation====
* create keys in order to avoid providing user and password for accessing Raspberry3B by <code>ssh-keygen // always enter</code>
* creates keyfile in <code>ls -al /home/uwe/.ssh/</code>
* copy key to Raspberry3B <code>ssh-copy-id root@192.168.178.35</code>
* test without entering password <code>ssh root@192.168.178.35</code>
* create a mount to Raspberry3B <code>mkdir -p ~/backup/mnt_raspberry3_for_backup</code>
* install sshfs <code>sudo apt install sshfs</code>
* mount with sshfs <code>sshfs root@192.168.178.35:/media/usbstick/backup /home/uwe/backup/mnt_raspberry3_for_backup</code>
* make it boot save by adding a row by <code>sudo nano /etc/fstab</code>
* decomment allow_other in <code>sudo nano /etc/fuse.conf</code>
* create <code>/home/uwe/backup/Raspberry3B/backup_raspberry3.sh</code>
** copies files from raspberry 3 to raspberry 4 by <code>cp -u -p /home/uwe/backup/mnt_raspberry3_for_backup/owncloud/owncloud_backup.zip /home/uwe/backup/Raspberry3B/owncloud/</code>
*** -u := only if new
*** -p := preserve file attributes in particular timestamps
** copies files to Google Drive by <code>rclone copy /home/uwe/backup/Raspberry3B/owncloud/owncloud_backup.zip uh_gdrive_backup:/Raspberry3B/owncloud/</code>
***rclone copy will only copy files that are new or have changed.
***the comparison is done using file size and modification time (mtime).
** writes log file <code>/home/uwe/backup/Raspberry3B/backup_raspberry3.log</code>
* schedule job which runs every night at 4 by <code>crontab -e</code> with <code>nice</code> to maintain responsiveness of the system
* check by <code>sudo crontab -l</code>