[Buildroot] Built a file system, have a working kernel - how to login ?

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Dear Juha Lumme,

On Sat, 17 Nov 2012 17:22:27 +0900, Juha Lumme wrote:

> I'm new to buildroot, and actually also to creating linux systems. I really
> need help understanding some basics of how a system bring up should happen..
> I have been working on a custom system of mine, running currently on a
> reference HW from Olimex.
> 
> I have built a working kernel, and now I created a file system with
> buildroot with all the settings default. Well, I did change the default
> console to ttyAMA0, as that is passed to the kernel by the loader.

Which /dev management method did you choose in the Buildroot
configuration?

> Now, the system boots up to the mounting filesystem, and then just hangs
> there:
> .....
> [    3.130000] VFS: Mounted root (ext3 filesystem) on device 179:2.
> [    3.140000] Freeing init memory: 144K
> Starting logging: OK
> Starting network...
> ip: RTNETLINK answers: Operation not permitted
> ip: SIOCSIFFLAGS: Permission denied
> 
> (The whole boot log is here: http://paste.ubuntu.com/1364407/ )
> 
> Can someone please educate me a bit what are the steps needed to get a
> login prompt, and to be able to access the system ? I don't really
> understand how the TTY links in /dev/ work, and how I need to tie them to
> the kernel configuration..
> 
> My understanding is that inittab is the file I should modify.. Contents of
> that is:

No, you shouldn't have to modify the inittab file.

> # Startup the system
> null::sysinit:/bin/mount -t proc proc /proc
> null::sysinit:/bin/mount -o remount,rw / # REMOUNT_ROOTFS_RW
> null::sysinit:/bin/mkdir -p /dev/pts
> null::sysinit:/bin/mkdir -p /dev/shm
> null::sysinit:/bin/mount -a
> null::sysinit:/bin/hostname -F /etc/hostname
> # now run any rc scripts
> ::sysinit:/etc/init.d/rcS
> 
> # Put a getty on the sttyAMA0::respawn:/sbin/getty -L ttyAMA0 115200 vt100
> # GENERIC_SERIAL

If your inittab really looks like this, then there is no way it can
work: the line starting getty is commented out.

So:

 *) Do not modify the inittab

 *) Tell us what hardware you're using exactly, becausing depending on
    the hardware, the ttyXYZn to use is different.

 *) Tell us which /dev management style you've chosen. If you chose
    devtmpfs or mdev or udev, then make sure your kernel has
    CONFIG_DEVTMPFS + CONFIG_DEVTMPFS_MOUNT (Buildroot ensures that your
    kernel is built with those options if Buildroot is responsible for
    building your kernel, but if you build your kernel outside of
    Buildroot, it's your job).

Best regards,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com