Setting mem=768M on QNAP TS-221

Debian doesn't work on QNAP devices with 1 GB of RAM (i.e. QNAP TS-221 or Fujitsu Q703). Even though we reported this to the Linux kernel developers, they found it difficult to investigate this issue and it never got fixed. The best workaround is to add mem=768M to the kernel command line to limit the RAM.

QNAP firmware

If you have the QNAP firmware, you can make the change with the following commands. These commands will:

  • Write the current u-boot configuration to /tmp/debian.uboot and add mem=768M to bootargs.
  • Output bootargs from the file so you can verify it looks good.
  • Write the new u-boot configuration to flash.
ubootcfg -b 0 -f /dev/mtdblock4 -o - | sed "s/^\(bootargs=.*\)/\1 mem=768M/" > /tmp/debian.uboot
grep "^bootargs" /tmp/debian.uboot # Check it looks sane
ubootcfg -b 0 -f /dev/mtdblock4 -i /tmp/debian.uboot


If you're running Debian (1 GB was working fine with Debian jessie), you can change the kernel arguments as follows.

sudo cp /usr/share/doc/u-boot-tools/examples/qnap_ts119-219.config /etc/fw_env.config
sudo fw_printenv bootargs

The output should be something like this:

bootargs=console=ttyS0,115200 root=/dev/ram initrd=0xa00000,0x900000 ramdisk=34816

You have to append mem=768M to these boot arguments in order to restrict the memory to 768 MB.

sudo fw_setenv bootargs "console=ttyS0,115200 root=/dev/ram initrd=0xa00000,0x900000 ramdisk=34816 mem=768M"

Finally, you can run sudo fw_printenv bootargs again to verify that mem=768M has been adding to the boot arguments.

Now you can either perform an upgrade or put the installer in flash and perform a new installation.