Update a UniFi Controller installation on Alpine Linux

unifi-update.sh

#!/bin/sh

####################################
# Update a UniFi Controller installation on Alpine Linux
#
# Assumes that the unifi service can be manipulated with "rc-service unifi <start/stop>"
#
# For initial installation see https://wiki.alpinelinux.org/wiki/UniFi_Controller
# Additional steps:
#  - apk add --no-cache libc6-compat
#  - ln -s /lib64/ld-linux-x86-64.so.2 /lib/ld-linux-x86-64.so.2

# Configuration options:

unifi_owner="unifi:unifi"
unifi_dir=~unifi
mongod_bin=/usr/bin/mongod
backup_file=~/unifi-data-$(date +%Y-%m-%d_%H%M%S).tar.gz

#####################################

set -eu

tmp="$(mktemp -d)"
trap 'rm -rf "$tmp"' EXIT INT TERM

update_file="$tmp/UniFi.unix.zip"

prompt(){
    _prompt="n"
    printf "%s [y/n] " "$1"
    read -r _prompt
    if ! [ "$_prompt" = "y" ]; then
        return 1
    fi
    return 0
}

download(){
    curr="$(cat "$unifi_dir/data/db/version")"
    echo "Installed version: $curr"

    data="$(curl -Ssf 'https://fw-update.ubnt.com/api/firmware?filter=eq~~product~~unifi-controller&filter=eq~~platform~~unix&filter=eq~~channel~~release&sort=-version&limit=1' | jq -r '._embedded.firmware[0]')"
    new=$(echo "$data" | jq -r '[.version_major, .version_minor, .version_patch] | join(".")' )
    echo "Latest version:    $new"
    if [ "$curr" = "$new" ]; then
        echo "No update available - exiting"
        exit 0
    fi

    if ! prompt "Apply update?"; then
        exit 1
    fi

    echo "Downloading..."
    wget "$(echo "$data" | jq -r '._links.data.href')" -O "$update_file"
}

backup(){
    echo "Backing up data to $backup_file"
    tar czf "$backup_file" -C "$unifi_dir/data" .
}

restore(){
    echo "Restoring data from $backup_file"

    if [ -e "$unifi_dir/data" ]; then
        rm -rf "$unifi_dir/data"
    fi
    mkdir -p "$unifi_dir/data"
    tar xzf "$backup_file" -C "$unifi_dir/data/"
}

update(){
    echo "Applying update"
    unzip -q "$update_file" -d "$tmp"

    rm -rf "$unifi_dir"
    mv "$tmp/UniFi" "$unifi_dir"

    chown "$unifi_owner" "$unifi_dir"
    chmod o-rwx "$unifi_dir"

    rm "$unifi_dir/bin/mongod"
    ln -s "$mongod_bin" "$unifi_dir/bin/mongod"
}

# Program start
download
rc-service unifi stop
backup
update
restore
rc-service unifi start