Getting Synology ActiveBackup for Business Working on Ubuntu 20.04

Background: Synology makes a great whole-computer backup system called ActiveBackup for Business. They added support for backing up Linux, but it doesn't work on kernels newer than 5.4. Ubuntu 20.04.4 is on 5.13.

These are the commands I used to get ActiveBackup 2.3.0-2153 working.

# Figure out latest version of 5.4 kernel
apt-cache showpkg linux-image | grep image-5.4 | grep generic | sort --version-sort
 
# Install that kernel
sudo apt install linux-image-5.4.0-107-generic --install-suggests

Edit the /etc/default/grub file. Change the GRUB_DEFAULT option to GRUB_DEFAULT=saved and add GRUB_SAVEDEFAULT=true.

If the GRUB_TIMEOUT_STYLE is set to hidden then change it to menu. Change the GRUB_TIMEOUT to 5.

# apply the changes we made to grub
sudo update-grub
 
# reboot, and hold the shift key while rebooting so you can pick the older version of the kernel (look at the Advanced Options boot menu)

# Make a directory to work in
mkdir syno
cd syno
 
# Download and unzip the correct version of the ABB agent
wget https://global.download.synology.com/download/Utility/ActiveBackupBusinessAgent/2.3.0-2153/Linux/x86_64/Synology%20Active%20Backup%20for%20Business%20Agent-2.3.0-2153-x64-deb.zip
unzip Synology\ Active\ Backup\ for\ Business\ Agent-2.3.0-2153-x64-deb.zip
 
# Run the installer
sudo ./install.run
 
# Run the configuration command
sudo abb-cli -c

Run the backup task and you should be good to go.

I'm not sure if this will keep the kernel up-to-date. I posted a question about it (https://askubuntu.com/questions/1403073/how-to-pin-a-specific-major-version-of-a-kernel/1403081#1403081) and I'll try it out when I can.