Release bz File Changes

Unraid OS is comprised of a set of 5 so-called bz files in the root of the USB Flash boot device:

  • bzimage - the Linux kernel
  • bzroot - the root file system, sans console desktop
  • bzroot-gui - additional files needed for the console desktop
  • bzmodules - modules (drivers) associated with the Linux kernel
  • bzfirmware - device firmware required by certain modules

Starting with 6.12 release, the content of these files has been rearranged:

  • bzimage - the Linux kernel (same as before)
  • bzroot - the root file system excluding the /usr directory tree
  • bzroot-gui - a single file that auto-starts the console desktop (for compatibility)
  • bzmodules - modules (drivers) associated with the Linux kernel and device firmware required by certain modules
  • bzfirmware - the /usr directory and all files contained therein, including the console desktop

The result of this change is to speed up the boot process and free up nearly 1G of RAM. It also permits us to add more "stuff" to Unraid OS in the future without requiring more RAM. Finally, when booted in non-GUI mode, the desktop can be started by logging in at the console and typig the 'slim' command.

The files bzfirmware and bzmodules are squashfs images mounted using overlayfs at /usr and /lib, respectively. Since these files are loopback-mounted, care must be taken if you ever want to perform a manual update.

What is a manual update? This is a method of updating Unraid OS on your USB flash boot device without using the Tools/Update OS function. Typically one would either:

  • open a Terminal window, wget the release zip file, unzip the release, and then 'cp' the bz files to root of the boot device.


  • export the 'flash' share on your network and drag the bz files from a PC directly to the flash.

Either method, starting with 6.12 can fail because the bzfirmware file will be overwritten while it is still mounted - not good.

To get around this, you must first create a temp directory on the flash device and then 'mv' (or drag) all the bz files to this temp directly. Now you can copy the new bz files in place and reboot.

Back to Unraid 6.12.0-rc3 Release blog