Call fstrim for Docker virtual disk

docker-trim.sh

#!/bin/bash
# Credits for the idea to https://djs55.github.io/jekyll/update/2017/11/27/docker-for-mac-disk-space.html

get_size () {
    ls -alks $HOME/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.raw | awk '{print $1}'
}

reclaim_space () {
    docker run --rm -it --privileged --pid=host walkerlee/nsenter -t 1 -m -u -i -n fstrim /var/lib/docker
}

BEFORE=$(get_size)
echo "Before: $BEFORE bytes"

echo "Running fstrim on /var/lib/docker..."
reclaim_space

AFTER=$(get_size)
echo "After: $AFTER bytes"

RECLAIMED=$(($BEFORE - $AFTER))
echo "Reclaimed space: $RECLAIMED bytes"