Debian 10 (buster) is the last release to support QNAP TS-21x/TS-22x devices. These devices are not supported in Debian 11 (bullseye).
The reason is that the Linux kernel no longer fits into flash memory. These QNAP devices boot from a 16 MB flash chip. During the installation of Debian, we put the Linux kernel and a ramdisk (initramfs) into flash which in turn loads Debian from disk. Unfortunately, there's only 2 MB allocated for the kernel partition in flash, which is not enough to store a modern version of the Linux kernel.
Support for QNAP TS-21x/TS-22x was dropped from Debian 11 (bullseye) because of this limitation.
If you're running Debian on your QNAP TS-21x/TS-22x device, you have several options:
- Stay on Debian 10. This release will be supported until around August 2022.
- Upgrade to Debian 11 while keeping the kernel from Debian 10. Please see the release notes for instructions.
- Change the flash partition layout. Someone has done this successfully but someone would have to write instructions on how to do it.