What are exactly
mknod command parameters?
I want to create a jail in chroot. So I need to do:
mknod /var/chroot/bind/dev/null c 1 3 mknod /var/chroot/bind/dev/random c 1 8
mknod is creating a device file, usually to be located in the /dev branch, but not necessarily like your example shows.
The first parameter is telling which kind of device to create, here
c for character device. Other choices might be
b for block devices,
p for fifo (pipe).
The second parameter is the major number, it identifies the driver for the kernel to use.
The third parameter is the minor number, it is passed to the driver for its internal usage.
On Linux, major/minor numbers are documented here: devices.txt
So 1 is used for the so called memory devices handled by a single driver.
3 is representing the
null device which returns EOF when read and discard whatever is writen to it.
8 is representing the
random device which returns random numbers.
To get more information, you might to have a look to the device manual pages, e.g.
man -s 4 null man -s 4 random
MAKEDEV is the preferred way of creating device files which are not present. However sometimes the
MAKEDEV script will not know about the device file you wish to create. This is where the
mknod command comes in. In order to use
mknod you need to know the major and minor node numbers for the device you wish to create.
mknod /dev/ttyS0 c 4 64