Some of this information from kuroboxwiki:Brick
In the context of LinkStation hacking to brick a LinkStation means to render the LinkStation unusable. A bricked LinkStation does not boot any more, does not respond to requests (e.g. for serving data via Samba), enters EM Mode, and/or does cyclic reboots.
Effectively, the LinkStation is just a brick, which can only be used as a door stopper unless one can fix it.
Wiki articles which might result in bricking an LS are often, but not always marked with
There have been cases of users writing uploading an incompatible flash image. Please be sure of what you are doing, and be very careful when attempting to modify the contents of the flash memory.
It regularly happens that an LS is diagnosed as bricked, when it isn't. The most common error is to not follow the flashing or installation instructions and still leave some software firewall in place during install.
Fixing a Bricked LS
Re-animating a bricked LS depends on what went wrong or what was done wrong. Sometimes re-flashing the original or a hacked firmware & OS can help (see The LinkStation firmware flasher, Manually flash the LinkStation's firmware. Sometimes it is necessary to Disassemble the LinkStation, connect the disk to a PC and re-image the drive. See Recover a non working "bricked" Linkstation for instructions.
Watchdog timer resets during boot
The start of the daemon happens relatively late in the LS' boot procedure. Now, if someone added a time-consuming boot task (e.g. some long taking service startup) before the start of the daemon, the watchdog timer is not properly reset, and the LS cyclic reboots while still in the boot procedure.
This can be fixed by opening the LS, connecting the hard drive to some Linux machine, mounting the drive and removing the offending service startup from the rc boot sequence.
Linkstations/Kuroboxes that have been bricked due to bad flash memory contents can be restored by rewriting the flash memory with the correct contents. However, since the device can not be booted, this requires the use of JTAG.