Unattended-Upgrades on OpenWrt

The OpenWrt documentation mentions why for opkg upgrade it’s impossible to update all additional software with a single statement due to the potential lack of available space in the read-write partition. This means that to keep packages up-to-date an administrator needs to check the list of upgradable packages and update each package individually on a constant basis.

Since OpenWrt firmware stores the base system in a compressed read-only partition, any update to base system packages will be written in the read-write partition and therefore use more space than it would if it was just overwriting the older version in the compressed base system partition. It’s recommended to check the available space in internal flash memory, and the space requirements for updates of base system packages.

This lack of available space is often the case with smaller embedded devices. It should, therefore not be a problem to perform unattended-upgrades on larger routers with more space available. This is done by creating an unattended-upgrades script and adding a crontab entry. Use at your own risk.

The script updates the opkg package lists, upgrades all upgradable packages and reboots after a successful upgrade.

#!/bin/sh
#
# unattended-upgrades updates the opkg package lists, upgrades all
# upgradable packages and performs a reboot after a successful upgrade.
#
# Usage: /usr/local/bin/unattended-upgrades

alias log="logger -t unattended-upgrades"

opkg update

# upgrade netifd first as it causes drop out and system upgrade fails
opkg upgrade netifd
if [ $? -ne 0 ]; then
    log -p 2 "package uprade failed"
    exit 1
fi

packages=$(opkg list-upgradable | awk '{print $1}')
if [ -n "$packages" ]; then
    log "performing upgrade of $packages"
    opkg upgrade $packages
    if [ $? -eq 0 ]; then
        log -p 1 "package uprade successful, rebooting"
        exec reboot
    else
        log -p 2 "package uprade failed"
        exit 1
    fi
else
    log "no packages to upgrade"
fi

To have the script run at a regular interval an entry needs to be added to the crontab using crontab -e.

0 4 * * * /usr/local/bin/unattended-upgrades