From Technologic Systems Manuals
Note: The new nandctl binary will only allow one instance of nandctl to run.

If a script attempts to run nandctl while another copy of nandctl is already running, the binary will refuse to run.

This is different from previous versions that would allow for a race condition that could cause data corruption and filesystem damage. Some production processes use these old scripts included in the original TS-4800 image. Those scripts must also be modified to avoid calling nandctl while it is already running. In most cases those calls can be replaced with equivalents using the Linux dd utility instead, or in some cases the call can be dropped entirely. There are some rare cases where the existing nandctl instance must be killed in order to perform the lowest level activities, such as performing an xnandinit, but this drastic step is generally not necessary on systems already set up to use xnand2.