Last update: 2021.04.02

Backup! Backup! Backup!

I have two r-pi booting from SSD drives instead of SD cards. Now, I want to triger rsync from r-pi A and have both r-pi A and r-pi B (the full SSD boot drive) copied on an external NAT drive connected to r-pi A.

For this project, I will use rsnapshot to make automated periodic copies.

Step 1: multiple sshd instance

When I need access to the r-pi from my laptop or my mobile phone, I connect through ssh with a rsa key secured by a strong password. For this project, we need to allow r-pi A to connect to r-pi B through ssh, but we will use another sshd instance and connect using a rsa key without password.

First, let’s create a secondary sshd instance to open a connection between r-pi A and B.

- On the r-pi B -

Change directory

cd /etc/ssh

Copy the sshd_config file as sshd-internal_config or using whatever name you like

sudo cp sshd_config sshd-internal_config

Edit sshd-internal_config

sudo nano sshd-internal_config

Change the port number (22555 is an example). Just make it different than the default port (usually 22) or any other port already in use.

Change directory

cd /lib/systemd/system

Copy the ssh.service file as ssh-internal.service or using whatever name you like

sudo cp ssh.service ssh-internal.service

Edit ssh-internal.service

sudo nano ssh-internal.service

Add the following

[Unit]
Description=OpenBSD Secure Shell server
After=network.target auditd.service
ConditionPathExists=!/etc/ssh/sshd_not_to_be_run

[Service]
EnvironmentFile=-/etc/default/ssh
PIDFile=/var/run/ssh-internal.pid
ExecStart=/usr/sbin/sshd -D -f /etc/ssh/sshd-internal_config $SSHD_OPTS
ExecReload=/bin/kill -HUP $MAINPID
KillMode=process
Restart=on-failure

[Install]
WantedBy=multi-user.target
Alias=<strong>sshd-internal.service</strong>

Enable ssh-internal.service

sudo systemctl enable ssh-internal.service

You should see the following

Reboot

sudo reboot

And make sure everything is running normally

sudo systemctl status ssh-internal.service

You should see something like

- On the r-pi A -

If necessary, create a .ssh directory

sudo mkdir ~/.ssh

Change directory

cd ~/.ssh

Create a rsa key

ssh-keygen -t rsa -b 1024 -f ./pi-squid-rsnapshot-key

Set permissions

sudo chmod 700 ~/.ssh
sudo chmod 600 ~/.ssh/*-rsnapshot-key

Create a new config file

sudo nano ~/.ssh/config

And add the following (adjust as needed)

Host remotehost-rsnapshot-pi-squid
Hostname 192.168.1.xxx
port 22555
IdentityFile ~/.ssh/pi-squid-rsnapshot-key

And in the host config file

sudo nano /etc/hosts

Put a new line at the end

192.168.1.xxx   remotehost-rsnapshot-pi-squid

Reboot

And test that you can connect with a simple command line

ssh remotehost-rsnapshot-pi-squid

Reference

https://iotalot.com/2017/03/01/how-to-run-multiple-sshd-instances-on-raspberry-pi/

Step 2: rsnapshot

- On the r-pi A -

Install rsnapshot

sudo apt-get install rsnapshot

Edit the rsnapshot configuration file

sudo nano /etc/rsnapshot.conf

What’s important is (edit as needed, these are my settings)

Where you want the backup to be stored

snapshot_root   /media/nextcloud/shared/backup/

How many backups do you want on a daily, weekly, monthly basis

retain  daily   7
retain  weekly  4
retain  monthly 12

The arguments to be passed to the command for ssh to work (edit your port number and USER as needed)

ssh_args        -p 22555 -i /home/USER/.ssh/pi-squid-rsnapshot-key

Exclude some directories from the copy (again, edit as needed)

exclude         /dev/*
exclude         /media/*
exclude         /proc/*
exclude         /sys/*
exclude         /run/*
exclude         /var/tmp/*
exclude         /var/run/*
exclude         /tmp/*
exclude         /lost+found/*

Define what you want to be backed up. It can be a few selectd directory, or the whole system as below

To backup r-pi A (local)

backup  /	destination_directory_name/

To backup r-pi B (remote)

backup  USER@remotehost-rsnapshot-pi-squid:/	destination_directory_name/

See down below my rsnapshot.con file for reference

Test your configuration syntax

sudo rsnapshot configtest

You should see

Syntax OK

Do a “dry-run” test of the backup process

sudo rsnapshot -v -c /etc/rsnapshot.conf daily

WHen happy, use the cron to schedule your backup processes

Daily: at 1 am
Weekly: every monday at 2 am
Monthly: every first monday of the month at 3 am

0 1 * * *               root    /usr/bin/rsnapshot daily
0 2 * * 1               root    /usr/bin/rsnapshot weekly
0 3 1 * *               root    /usr/bin/rsnapshot monthly

You can also launch the process manually, with or without the cverbose (-v) argument

sudo rsnapshot -v daily

Tip

If you use Nextcloud, you can install Samba and share your backup directory as a shared folder.

Reference

https://wiki.gentoo.org/wiki/Advanced_backup_using_rsnaphot#Configuration
https://dvpizone.wordpress.com/2014/03/08/using-rsnapshot-with-a-raspberry-pi-to-create-a-backup-device/
https://ubuntu.com/server/docs/tools-rsnapshot

rsnapshot - my full config file

config_version  1.2

snapshot_root /media/nextcloud/shared/backup/

no_create_root  1

cmd_cp    /bin/cp
cmd_rm    /bin/rm
cmd_rsync /usr/bin/rsync
cmd_ssh /usr/bin/ssh
cmd_logger  /usr/bin/logger
cmd_du    /usr/bin/du

retain  daily 7
retain  weekly  4
retain  monthly 12

verbose   2
loglevel  3

lockfile  /var/run/rsnapshot.pid

ssh_args  -p 22555 -i /home/USER/.ssh/pi-squid-rsnapshot-key

one_fs    1

exclude   /dev/*
exclude   /media/*
exclude   /proc/*
exclude   /sys/*
exclude   /run/*
exclude   /var/tmp/*
exclude   /var/run/*
exclude   /tmp/*
exclude   /lost+found/*

backup    /					mizuki-serv/
backup 	  USER@remotehost-rsnapshot-pi-squid:/	pi-squid/