udev timeout during boot

[javeree]

I set up a system to boot from a usb drive (while chrooting, this is /dev/sdb1).
I can start with the bios starting grub2 on the usb stick. Grub2 calls the kernel and the initramfs (I can see that at this point that the usb partition is now recognized as sda1 and mounted). initram does switch_root and starts init.

On the step 'Waiting for uevents to be processed', I have to wait over a minute, after which I get:

[BillWho]

javeree,

Check the .config settings
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y

If that's OK then is there anything installed on sda?

If possible, save your sda mbr and try to install grub to it. Make any appropriate changes, if necessary, to fstab and see if it boots without udev errors.
_________________
Good luck

Since installing gentoo, my life has become one long emerge

[javeree]

I checked just before going to work:
yes, both CONFIG options are =y

'is something installed on sda?':
yes, I chrooted to the usb disk and installed a complete gentoo installation, includign all the services I will need. Grub2, the kernel and initramfs are located on that same usb.

The internal disk is a small read-only disk with a small windows version flashed in meant serve as a thin client. I can not write to that using normal means, so installing grub to the internal drive is not possible. (I would have to install grub to a file that serves as a disk image and then flash that disk image onto the internal drive). I prefer grub on the usb drive.

When the error occurs, grub2 has already fulfilled its function: calling the kernel, so in my opinion, it should have no effect anymore influencing the boot.

The kernel has already run initramfs. In initramfs, I mount the usb disk by its uuid by trying in a loop: 'findfs xxxx-xxx-xxx'.
findfs fails a few times until the kernel sees the usb drive, then it returns /dev/sda.

This is a point where I have some doubts: why is the usb recognized as sda1, when there is also an internal disk ? When I use netboot, the internal disk is /dev/sda1 and the usb disk is /dev/sdb1.

If I understand the boot process with initramfs correctly, this step to mount root should be sufficient, and fstab would never be accessed again to boot (and definitly not before udev has initialized). So here in my opinion fstab should also not be the culprit. It might as wel be empty (FYI, there is just one partition with / /boot /usr /home ...)

I have a feeeling that udev fails because it is still waiting for something that I have failed to activate in the kernel and that udev wants to run after it has detected the drive. Maybe 'blkid' or 'udisks-part-id' need a specific kernel setting ?

Also FYI, as you can see I use EXT4, and have compiled ext4 in the kernel, so that is an obvious one.
I am rather thinking about the kernel settings related to usb/scsi/(s)ata ...

[javeree]

Something I'll try when I get home tonight: I've read that udisks requires CONFIG_SWAP, which I had deactivated, because this system has no swap. I'll report on the result

[javeree]

udev still fails in the same way, but at least I got my system booting.
after udev fails there is no drive by uuid defined, so I had to change /etc/sftab to refer to /dev/sda1.

/etc/init.d/root still complains that it cannot remount / read-write, but teh system now continues to boot happily.
When it gives me a login, I can write to / without problems.

Remarkably, the PC is a real snail (it takes several minutes to boot, vi /etc/fstab sometimes take up to 10 second, ...), which is not the Pcs fault, because it is very fast whan I boot it using e.g. partedmagic.

Probably the PC being extremely slow causes the timeout in udev, so now the task is to find out what is the bottleneck: IO on the USB drive, the CPU being throttled back, some resource shortage, ...
So far, I have not found anything suspicious yet.