Keeping the Router Updated

Let the router tell us when there are updates available.

Software Packages

The excellent opkg upgrade script from Gustavo Arnosti Neves.

The router must be able to send out mails.

Installing the Script

router$ opkg install ca-certificates openssl-util

router$ wget '' \
    -O "/tmp/"
router$ chmod 755 "/tmp/"
router$ /tmp/ --install

Checking for Updates

router$ opkg-upgrade

Cron Job

Let’s create a scheduled job, that checks for updated packages every 16 hours, and notifies us by mail:

router$ EDITOR=$(which nano) crontab -e

Insert the line as follows:

1 # Send any output by mail to
3 #
4 #min hour mday month wday cmd
5 35   */16 *    *     *    /usr/sbin/opkg-upgrade --text-only --ssmtp
7 # crontab and fstab must end with the last line a space or comment

Use CTRL+X and Y to save and exit.

Restart cron to re-read its configuration:

router$ /etc/init.d/cron restart

OpenWRT Releases

No automation here.

You need to follow the OpenWrt Project page.

Firmware Download

The OpenWRT firmware images have a checksum to verify its integrity after download.

The file containing the checksum are signed with an OpenPGP key. The OpenWRT team uses a distinct “release signing key” to sign the checksum files of a major OpenWRT release and subsequent point releases.

The release keys are published on the OpenWrtPublic Keys page.

So the steps necessary to download and verify a firmware image:

  1. Find appropriate firmware image file on the download site or one of the mirror sites.

  2. Download the image file.

  3. Download the checksum file (found at the bottom of the download page).

  4. Download the OpenPGP signature file of the checksum file (also found at the bottom of the download page).

  5. Download the public OpenPGP release key from the OpenWrtPublic Keys page

  6. Add the release key to your public keyring, set trust and sign it locally.

  7. Verify the OpenPGP signature of the checksum file.

  8. Verify the integrity of the image file with the checksum file.

Thats a lot of work. Fortunately there is a script which takes care of all the steps, except the first one.

OpenWRT supplies a convenience script to automate the required download and signature verification steps.

With the download script its enough to supply the URL of the firmware image to download:

desktop$ cd ~/Downloads
desktop$ wget -O
desktop$ chmod 755
desktop$ ./

Transfer the verified image to the router:

desktop$ scp openwrt-18.06.0-ar71xx-generic-wndr3800-squashfs-sysupgrade.bin \


Make sure you have all your relevant config-files listed in the /etc/sysupgrade.conf file on the router:

router$ less /etc/sysupgrade.conf

Make sure you have all your user-installed packages listed in the file /root/opkg-user-installed.txt:

router$ awk '/^Package:/{PKG= $2} /^Status: .*user installed/{print PKG}' /usr/lib/opkg/status \
    > /root/opkg-user-installed.txt

Make one last backup before starting the system upgrade procedure:

router$ /root/

Firmware Upgrade

router$ sysupgrade -v /tmp/sysupgrade.bin