Tag: Kernel

Raspberry PI 4 Boot from USB HDD not working GPT

This is more of a note for me than a guide or help for anyone else.

At present the PI4 does NOT support boot from USB, but you can work around this like the old days by using an SD card for the /boot and setting this to load the root from USB Stick/HDD.

However, this only appears to work for me using MBR partition type and just hangs when using GPT. This may be because I’m also encrypting the disk and using headless network boot. But that side does work and the disk/paritions are decrypt and list in /dev/disk/by-label but the OS just will NOT boot for me. Copying everything to the exact same partition layout and labels under MBR and it just works.

It seems a weird problem, as the SD card that’s actually booting and has the kernel is MBR and I don’t see why it would then care, the kernel has to be aware of GPT and as I said lists everything correctly. I can even decrypt and mount during the dropbear network boot bit, but the OS just wont boot. Workaround at present is to place the OS on it’s own drive/stick and use GPT on bigger disks purely for data. I’ve only found this while trying to use a 5Tb disk for both OS and Data. the 2Tb disk I can use MBR on without loosing space so the workaround isn’t really needed, just use MBR.

Ubuntu Graphics Problems

I ran into this problem a while back on my server but it’s never really affected me as I dont generally use the console.

After running updates a good few months back, my system stopped giving me any output. It wouldn’t load to X or a console and even stopped showing the splash screen and the boot info.

The way I was getting around it was to just use an earlier Kernel version during boot. But tonight while doing some work this little bugger got me again.

After hours working through numerous problems I’ve just left unresolved this one finally needed to be solved. Previously I’d just SSH’d to the machine having no console, started the xlib_shm stuff and up popped the CCTV view and I’d just leave that running, but tonight even that wouldn’t work.

I found the following info while trawling the interweb for fixes:-
The problem seems to start after Kernel 2.6.38-8 (that’s the last one I can boot without problems)
It’s related to the ATI graphics card and drivers
*ERROR* Failed to register bit i2c VGA_DDC was showing up in the syslog

I found info in several bugs saying to add this ‘i2c_algo_bit.bit_test=0’ but didn’t actually say where.
https://bugzilla.novell.com/show_bug.cgi?id=691052
http://lists.freedesktop.org/archives/dri-devel/2011-June/012061.html
http://forums.opensuse.org/english/get-technical-help-here/install-boot-login/459015-no-display-after-online-update-4.html

So I opted to add ‘i2c_algo_bit.bit_test=0’ into the grub config for the lastest kernel, so my grub line now looks like ‘linux   /vmlinuz-2.6.38-15-generic root=/dev/mapper/VG-LV_Root ro   quiet splash i2c-algo-bit.bit_test=0 vt.handoff=7’

Rebooting kept my splashscreen, and presented me with my console once again. and now my xlib_shm was also working once again.

But as I’m very likely to forget after a bunch more remote updates, I thought it best to make it a little more permanent, so I edited /etc/default/grub and amended the OPTIONS line to read ‘GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash i2c-algo-bit.bit_test=0″‘
a quick run of update-grub and my entire config is updated.
This should survive future updates and keep me with a working console should I need it.