🚀 Custom OpenWRT Image Build & VM Conversion Script

A repeatable approach to custom OpenWRT image creation:

• Manage & track your OpenWRT build recipes
• Optionally resize default partitions to unlock extra root filesystem storage
• Optionally convert OpenWRT images into into QEMU, Virtualbox, HyperV or VMware images
• Automatic installation of OpenWRT Imagebuilder dependencies

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⚙️ Script Option Prompts

1. Enter OpenWRT STABLE release version (or hit enter for latest snapshot)

2. Modify partition sizes or keep OpenWRT defaults? [y/n] (Y = follow the prompts)

3. Enter an image filename tag (to uniquely identify your new image)

4. Optional: Convert OpenWRT images to VM disk image? [y/n] (Y = select a VM format: qcow2, qed, vdi, vhdx or vmdk)

5. Optional: Bake a custom OpenWRT config into new OpenWRT images? (follow the prompts)

6. When the script completes new images are located at:

   • Native Firmware: $(pwd)/openwrt_build_output/firmware_images
   • Virtual Machine:$(pwd)/openwrt_build_output/vm

   

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🛠️ Prerequisites

Any recent x86 Debian-flavored OS with the sudo package installed should be fine.

• All image building dependencies are automatically installed on first run.
• If building old OpenWRT versions (< = 19.x), using a Linux distro from the same era will save you some troubles with older Python build machine prerequisities.
• Windows subsystem for Linux users have additional steps. See below WSL section

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📖 Instructions

1. 📥 Download the image builder script and make it executable:

   chmod +x x86-imagebuilder.sh
   

2. 🛠️ Customise your package recipie in the CUSTOM_PACKAGES section at the top of the script.

   • The included default packages are examples only and can be changed.
   • If you have issues with your build, check screen output for package selection errors or conflicts.

3. ▶️ Run the script without sudo (it will prompt for sudo) and follow the prompts:

   ./x86-imagebuilder.sh
   

4. VMware ESXi VM users only: Please see here for final ESXi VM conversion steps.

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📂 Persistent filesystem expansion WITHOUT resizing partitions

It is possible to add a large persistent EXT4 data partition that, unike any resized partitions, won't be wiped by a reset or sysupgrade.

1. Add a usb drive (or vdisk) with an EXT4 partition and mount this with:

   block detect | uci import fstab
   uci set fstab.@mount[-1].enabled='1'
   uci commit fstab
   reboot
   

Alternately, in Luci see http://your-routername/cgi-bin/luci/admin/system/mounts to mount the new disk via gui.

2. From OpenWRT, copy the (now updated) /etc/fstab file
3. Re-run the build script, this time adding the copied /etc/fstab file to $(pwd)/openwrt_inject_files when prompted.
   • The updated fstab file referencing the extra EXT4 partition will now be baked into the new build, making this storage persistent after a reset or sysupgrade.
4. Update to this new build

🌐 Sysupgrades with x86

• OpenWRT 23.x and below: If resizing partitions, attended sysupgrade returns the default partition schema - which will likely be a bad thing! Instead, for x86 upgrades you must recreate a new image and re-flash.
• OpenWRT Version 24.x onwards: Supports attended sysupgrade with a resized root partitions up to 1024mb (with a few extra config settings).

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🛠️ Windows Subsystem for Linux Users: (tested WSL Debian 12).

1. OpenWRT Imagebuilder needs a CASE SENSITIVE filesysyem
   • From within Windows, create a new working directory for the script (eg. C:\users\%username%\OWRT)
   • From powershell fsutil.exe file setCaseSensitiveInfo "C:\users\%username%\OWRT" enable
2. Remove Windows paths from Debian $PATH (spaces in paths breaks things)

sudo tee -a /etc/wsl.conf << EOF > /dev/null
[interop]
appendWindowsPath = false
EOF
exit

3. Shutdown Debian wsl --shutdown
4. Restart Debian wsl -d Debian
5. From Windows or Debian, copy/save the build script x86-imagebuilder.sh to the newly created working dir above
6. In Debian, change to the new working dir and make the script executable chmod +x x86-imagebuilder.sh
7. From the new working dir in Debian, run the script with ./x86-imagebuilder.sh See here for more about OpenWRT Imagebuilder & WSL: https://openwrt.org/docs/guide-developer/toolchain/wsl

⚠️ WARNING: Resize of OpenWRT partitions on flash memory devices

• For OpenWRT experts only:
  • Partition resize is for x86 builds. (You’ll need to manually edit the script for other architectures).
  • Know what you are doing (use this script at your own risk).
  • Resizing firmware partitions on router flash will likely brick your device!!
  • Have a plan to unbrick before proceeding.