root@debian6:/dev# ls -lL /dev |sort |grep '^c' |grep 1,
crw------- 1 root root 1, 11 Mar 11 22:45 kmsg
crw-r----- 1 root kmem 1, 1 Mar 11 22:45 mem
crw-r----- 1 root kmem 1, 4 Mar 11 22:45 port
crw-rw-rw- 1 root root 1, 3 Mar 11 22:45 null
crw-rw-rw- 1 root root 1, 5 Mar 11 22:45 zero
crw-rw-rw- 1 root root 1, 7 Mar 11 22:45 full
crw-rw-rw- 1 root root 1, 8 Mar 11 22:45 random
crw-rw-rw- 1 root root 1, 9 Mar 11 22:45 urandom
crw-rw---- 1 root cdrom 21, 1 Mar 11 22:45 sg1
crw-rw---- 1 root cdrom 21, 2 Mar 11 22:45 sg2
主 次设备号
主设备号用来区分设备的种类，次设备号作为唯一性区分----参考百度百科
关于文件系统的3个目录：/dev /proc /sys
mknod - make block or character special files
mknod [OPTION]... NAME TYPE [MAJOR MINOR]
-m, --mode=MODE TYPE
set file permission bits to MODE, not a=rw - umask
TYPE：
b create a block (buffered) special file
c, u create a character (unbuffered) special file
p create a FIFO
mknod -m 600 /dev/console c 5 1
mknod -n 666 /dev/null c 1 3