Backup

Connect via ssh

ssh user@host

Enter the password when prompted.

Shutdown

sudo shutdown now

Insert sd card into computer

Remove the sd card from the Raspberry Pi once it has powered off. Then insert it into your computer.

These instructions work for macOS only.

Find device name of mounted sd card

diskutil list

Look for a device that matches the size of your sd card. The device probably has a partition called boot.

The device will be called something like /dev/disk2.

Make backup

sudo dd if=/dev/disk2 of=~/Desktop/backup.dmg

Including useful information like the current date or content of the backup in the filename might be a good idea.

This command can take some time and will not indicate any progress - just hang on.

Eject sd card

sudo diskutil eject /dev/disk2

Restore

Insert sd card and identify device name

Find device name as described here.

Unmount sd card

diskutil unmountDisk /dev/disk2

Restore backup

sudo dd if=~/Desktop/backup.dmg of=/dev/disk2

This command can take some time and will not indicate any progress - just hang on.

Eject sd card

sudo diskutil eject /dev/disk2