null(4) -- Linux man page
NAMEnull, zero - data sink
DESCRIPTIONData written on a null or zero special file is discarded.
Reads from the null special file always return end of file, whereas reads from zero always return \0 characters.
null and zero are typically created by:
mknod -m 666 /dev/null c 1 3
mknod -m 666 /dev/zero c 1 5
chown root:mem /dev/null /dev/zero
NOTESIf these devices are not writable and readable for all users, many programs will act strange.
SEE ALSOchown(1), mknod(1)