Apparantly this stems from a limitation in the kernel regarding the size of command arguments. The
Argument list is too long error message is typically shown if you try to run a command on a large filelist (for instance targeting files in a huge directory using wildcards), because the Linux kernel will split every target file found as separate arguments.
Say you have a directory containing three files; file1.txt, file2.txt, file3.txt. Running the command
rm * in this directory will actually be interpreted as
rm file1.txt file2.txt file3.txt by the kernel.
Two quick solutions comes to mind.
Using a for loop:
for f in /home/itdb/deleteme/*; do rm "$f"; done
Using the find command:
find /home/itdb/deleteme -name "*" -delete
For more information, check out this stackoverflow question: