Creating devices with Make_devices-&makedev-version;
The Make_devices package contains a script for creating device
nodes.
&buildtime; &makedev-time;
&diskspace; &makedev-compsize;
&aa-makedev-down;
&aa-makedev-dep;
Making devices
Note that unpacking the
make_devices-&makedev-version;.bz2 file doesn't
create a directory for you to cd into, as the file
contains only a shell script.
Install the make_devices script:
bzcat make_devices-&makedev-version;.bz2 > /dev/make_devices
chmod 754 /dev/make_devices
Device nodes are special files: things that can generate or receive data.
They usually correspond to physical pieces of hardware. Device nodes can be
created by issuing commands of the form: mknod -m mode name type major
minor. In such a command, mode is the usual
octal read/write/execute permissions triplet, and name is
the name of the device file to be created. It may seem surprising, but the
device name is actually arbitrary, except that most programs rely on devices
such as /dev/null having their usual names. The remaining
three parameters tell the kernel what device the node
actually refers to. The type is a letter, either b or c,
indicating whether the device is accessed in blocks (such as a hard disk) or
character by character (such as the console). And major
and minor are numbers, together forming a code that
identifies the device to the kernel. A list of the currently assigned device
numbers for Linux can be found in the file devices.txt in
the Documentation subdirectory of the
kernel sources.
Note that the same major/minor combination is usually assigned to both a
block and a character device. These are, however, completely unrelated devices
that cannot be interchanged. A device is identified by the type/major/minor
triple, not just the major/minor pair, so when creating a device node it is
important to choose the correct type of device.
Because looking up the type/major/minor triples and using
mknod manually is tedious and error-prone, the
make_devices script has been created. It contains a whole
series of mknod commands, one for each device, complete with
recommended name, permissions and group assignment. It has been set up so that
only a minimal set of commonly used devices is enabled and the other lines are
commented out. You should open make_devices in an editor
and customize it to your needs. This takes some time, but is very simple. When
you are satisfied, run the script to create the device files:
cd /dev
./make_devices
If you had success with mounting the devpts file system earlier in , you can continue with the next section. If you were
unable to mount devpts, you will have to create a few static ptyXX and ttyXX
device nodes instead. To do this, open make_devices in
your editor, go to the section "Pseudo-TTY masters" and enable a few ptyXX
devices -- a handful are enough to enable the test suites to run, but if you
plan to run a kernel without devpts support you will probably need many more
(every xterm, ssh connection, telnet connection, and the like, uses one of
these pseudo terminals). In the immediately following section "Pseudo-TTY
slaves", enable the corresponding ttyXX devices. When you are done, rerun
./make_devices from inside /dev to
have it create the new devices.
&aa-makedev-shortdesc;
&aa-makedev-desc;