/dev/full returns ENOSPC when written to and returns a stream of zeroes (similar to /dev/zero) when read. $ echo x > /dev/full -bash: echo: write error: No space left on device $ dd if=/dev/full bs=20 count=1 2>/dev/null | xxd -i 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
/dev/full is created in drivers/char/mem.c.