On Wed, May 06, 2015 at 11:51:09PM +0100, linuxcbon linuxcbon wrote:
> On Wed, May 6, 2015 at 10:31 PM, Bernhard Reutner-Fischer
> <[email protected]> wrote:
> > http://git.busybox.net/buildroot/tree/target/generic/target_busybox_skeleton/etc/inittab?id=9e59c9bc006734237510e8bbb36e83ed429cd03f
> > Probably a bit out of date by now, but you get the idea.
> > HTH,
> 
> Hi Bernhard,
> I have tried this already, didnt work...so I must try again until I
> find out where it didnt work.

A more precise description of what happened than "didn't work" would
be more helpful.


If you need to get up to speed on mdev, you can read the following
documentation in the Busybox source tree:
docs/mdev.txt
examples/mdev*

> Can you please tell me how to have as many debug infos from mdev and kernel
>  as possible so I can find where I got it wrong ?

touch /dev/mdev.log
cat >/sbin/mdev.logger <<EOF
#!/bin/busybox ash
echo "---" >>/dev/hotplug.log
env >>/dev/hotplug.log
exec /sbin/mdev
EOF
chmod +x /sbin/mdev.logger
echo /sbin/mdev.logger >/proc/sys/kernel/hotplug


This will give you two logs:
/dev/mdev.log contains a record of what mdev did, and /dev/hotplug.log
records the environment.

> By the way, I dont need "mdev -s" because I mount devtmpfs right ?

mdev -s is required to set the permissions and execute the helper
scripts specified in mdev.conf; if you don't need those, you don't
need to run it (but then you probably wouldn't need mdev at all).

> Other question, isnt pts optional ?

If you don't need *any* terminal emulation, it's optional.
xterm, ssh, telnet, and possibly emacs need it.

> Where does mdev find the rules in which folder ?
> Can I have mdev detect my radeon and do the correct modprobes and how ?
> Same for sound and network.
> And does it need a /run folder mandatory ?

The following files and directories are relevant to mdev:
/sys: must be mounted
/dev: must be writeable
/etc/mdev.conf: must be readable if you use it
/dev/mdev.seq: should be rw if present; serializes hotplug events
/dev/mdev.log: used for logging hotplug events if it is writeable

and your kernel must be set to use mdev as the hotplug helper,
via writing to  /proc/sys/kernel/hotplug, or using an equivalent
sysctl invocation or option to the kernel.
/run is not involved, nor is anything in /var.

Typically you will want "helpers", which are usually installed in
/lib/mdev/.

The Alpine Linux configuration and initscripts can be found here:
http://git.alpinelinux.org/cgit/aports/tree/main/busybox-initscripts/mdev.conf
http://git.alpinelinux.org/cgit/aports/tree/main/busybox-initscripts/mdev.initd
http://git.alpinelinux.org/cgit/aports/tree/main/busybox-initscripts
helpers are the scripts named *dev and *_links

> (Sorry for those questions, I never used mdev before...)

Read docs/mdev.txt!


HTH,
Isaac Dunham
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