The Udev package contains programs for dynamic creation of device nodes.
Create some devices and directories that Udev cannot handle due to them being required very early in the boot process:
install -dv /lib/{firmware,udev/devices/{pts,shm}}
mknod -m0666 /lib/udev/devices/null c 1 3
ln -sv /proc/self/fd /lib/udev/devices/fd
ln -sv /proc/self/fd/0 /lib/udev/devices/stdin
ln -sv /proc/self/fd/1 /lib/udev/devices/stdout
ln -sv /proc/self/fd/2 /lib/udev/devices/stderr
ln -sv /proc/kcore /lib/udev/devices/core
Compile the package:
make EXTRAS="extras/ata_id extras/cdrom_id extras/edd_id \
extras/firmware extras/floppy extras/scsi_id \
extras/usb_id extras/volume_id"
The meaning of the make option:
This builds several helper binaries that can aid in writing custom Udev rules.
To test the results, issue: make test.
Install the package:
make DESTDIR=/ \
EXTRAS="extras/ata_id extras/cdrom_id extras/edd_id \
extras/firmware extras/floppy extras/scsi_id \
extras/usb_id extras/volume_id" install
The meaning of the make parameter:
This prevents the Udev build process from killing any udevd processes that may be running on the host system.
Udev's configuration is far from ideal by default, so install the configuration files here:
cp -v ../udev-config-6.rules /etc/udev/rules.d/25-lfs.rules
Create some rules that work around broken sysfs attribute creation timing in linux-2.6.15:
cat >> /etc/udev/rules.d/10-wait_for_sysfs.rules << "EOF"
ACTION=="add", DEVPATH=="/devices/*", ENV{PHYSDEVBUS}=="?*", WAIT_FOR_SYSFS="bus"
ACTION=="add", SUBSYSTEM=="net", WAIT_FOR_SYSFS="address"
EOF
Install the documentation that explains how to create Udev rules:
install -m644 -D -v docs/writing_udev_rules/index.html /usr/share/doc/udev-088/index.html
![[Important]](../images/important.png)
When Udev is started by the LFS-Bootscripts, a replay of all kernel device events happens. These events tell Udev what devices exist. Sometimes the Udev bootscript doesn't wait long enough for udevd to process all of the replayed events and consequently the devices for those missed events are not created before the script exits. Since udevd is still running in the background, the devices will be created a few milliseconds later, but the next bootscript to run may require a device to exist before it has been created. To avoid such missed events, and to avoid hardcoding an overly long wait time, It is recommended that you run the following commands to aid the LFS development team in debugging these missed events and finding an acceptable solution more quickly.
First, create a simple C file:
cat > bug.c << EOF
/* Simple event recorder */
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <argz.h>
int main(int argc, char * argv[])
{
char * envz;
size_t len;
int bug;
bug = open("/dev/bug", O_WRONLY | O_APPEND);
if (bug == -1)
return 0;
setenv("_SEPARATOR", "--------------------------------------", 1);
argz_create(environ, &envz, &len);
argz_stringify(envz, len, '\n');
envz[len-1]='\n';
write(bug, envz, len);
close(bug);
free(envz);
return 0;
}
EOF
Now compile it:
gcc -o /lib/udev/bug bug.c
The next step adds a simple logging rule to run this program.
cat > /etc/udev/rules.d/90-bug.rules << "EOF" ACTION=="add", RUN+="bug" EOF
When booting the new LFS system, if any events are missed, a warning message will appear and a /dev/bugreport file will be created. The warning message will tell you where to send feedback.