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6.8. Populating /dev

6.8. Populating /dev

6.8.1. Creating Initial Device Nodes

When the kernel boots the system, it requires the presence of a few device nodes, in particular the console and null devices. The device nodes will be created on the hard disk so that they are available before udev has been started, and additionally when Linux is started in single user mode (hence the restrictive permissions on console). Create the devices by running the following commands:

mknod -m 600 /dev/console c 5 1
mknod -m 666 /dev/null c 1 3

6.8.2. Mounting tmpfs and Populating /dev

The recommended method of populating the /dev directory with devices is to mount a virtual filesystem (such as tmpfs) on the /dev directory, and allow the devices to be created dynamically on that virtual filesystem as they are detected or accessed. This is generally done during the boot process. Since this new system has not been booted, it is necessary to do what the LFS-Bootscripts package would otherwise do by mounting /dev:

mount -nvt tmpfs none /dev

The Udev package is what actually creates the devices in the /dev directory. Since it will not be installed until later on in the process, manually create the minimal set of device nodes needed to complete the building of this system:

mknod -m 622 /dev/console c 5 1
mknod -m 666 /dev/null c 1 3
mknod -m 666 /dev/zero c 1 5
mknod -m 666 /dev/ptmx c 5 2
mknod -m 666 /dev/tty c 5 0
mknod -m 444 /dev/random c 1 8
mknod -m 444 /dev/urandom c 1 9
chown -v root:tty /dev/{console,ptmx,tty}

There are some symlinks and directories required by LFS that are created during system startup by the LFS-Bootscripts package. Since this is a chroot environment and not a booted environment, those symlinks and directories need to be created here:

ln -sv /proc/self/fd /dev/fd
ln -sv /proc/self/fd/0 /dev/stdin
ln -sv /proc/self/fd/1 /dev/stdout
ln -sv /proc/self/fd/2 /dev/stderr
ln -sv /proc/kcore /dev/core
mkdir -v /dev/pts
mkdir -v /dev/shm

Finally, mount the proper virtual (kernel) file systems on the newly-created directories:

mount -vt devpts -o gid=4,mode=620 none /dev/pts
mount -vt tmpfs none /dev/shm

The mount commands executed above may result in the following warning message:

can't open /etc/fstab: No such file or directory.

This file—/etc/fstab—has not been created yet but is also not required for the file systems to be properly mounted. As such, the warning can be safely ignored.