initramfs confusion

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

Hi all

I was trying to use an initramfs so I could mount drives using a LABEL=gentoo_root parameter. I tried to follow the directions here:

https://forums.gentoo.org/viewtopic-t-850865.html?sid=d8eee5d0bd8e4282714c2937a4236ac6

and here:

http://en.gentoo-wiki.com/wiki/Initramfs

and my directory structure looks like this:

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

What is in /init in the initramfs? What happens if you build an initramfs using the built-in support, instead of bolting one on at boot time?

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

So, I decided to try back to basics. I went to the manual:

http://en.gentoo-wiki.com/wiki/Initramfs

and followed the directions up to Creating a Seperate File. My init contains:

whig · l33t Joined: 27 Nov 2004 Posts: 973 Location: New Zealand

Unless overridden I think we need a /sbin/init. It can be a link to another location. In your list it is missing.

Goverp · Advocate Joined: 07 Mar 2007 Posts: 2202

Have you done chmod +x /usr/src/initramfs/init ?
_________________
Greybeard

systema encephale · n00b Joined: 17 Apr 2006 Posts: 11

Same problem here. I have a VMWare ESX 3.0.1 environment, where I can install Gentoo VMs with kernels not newer than 2.6.20. Apparently this is the only kernel version I've found that fully supports the SCSI controller. Also, I have to use the old Gentoo 2007 minimal install live cd, otherwise newer releases don't work. The kernel modules are the Fusion-MPT mptbase.ko, mptscsih.ko and mptspi.ko, that maybe have changed since 2.6.20.
I've created the initramfs in /usr/src/initramfs and followed the steps described in http://en.gentoo-wiki.com/wiki/Initramfs. My init script is

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

I tried linking /sbin/init -> /init - no luck. I did chmod +x on /init. It is as though the initramfs file is just totally being ignored. I still tells me it can't find init or /sbin/init when I specify it.

Any other suggestions? Could this be some sort of bug with the 2.6.36 kernel? I dunno ---

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

I have used each of the last six major kernels (2.6.30, 2.6.31, etc.) with initramfs with no problems. My initial process is /init and is part of the kernel image, as built by CONFIG_INITRAMFS_SOURCE. It is activated automatically at boot, and transitions to my hard disk root filesystem after performing its work. I have never seen a kernel ignore an initramfs in the manner reported here.

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

Sorry - just sort of grasping at straws. I followed the manual except for changing the root drive to /dev/sde3, and it isn't working. I don't know how to debug it or figure out what is happening. I tried building it directly into the kernel and that did not work. I am hesitant to do that because the only way I know to fix that is to rebuild without the image. If I keep it as a seperate file, I can at least recover by commenting out the initrd line and add root=/dev/sde3 to the kernel line.

Thanks.

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

So - one thing I did find - if I omit the --format=newc option when making the cpio archive, I get a different result - it tells me it cant mount a file type / system. So, could I be doing something wrong there?

Another question - is there some way I can slow the messages down at boot so I can actually see what is going on?

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

I stumbled across the dracut utility while trying to dig up more answers. I tried it out and it appears to work - ie, I can mount by Label now. I'd like to leave this open for now though because I still would like to know what I did wrong / why I can't get the instructions from the wiki page to work.

Thanks again!

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

Can you run (as root) chroot /usr/src/initramfs /bin/busybox sh successfully? If not, what error does it print?

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

No - as root, it tells me:

chroot: failed to run command `/bin/busybox sh': No such file or directory

which is odd, because it is there. In fact, if I do just chroot /usr/src/initramfs, it tells me there is no /bin/bash - which is real odd and means I might have other issues.

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

After a little more digging - I found it meatn that I might not have the right libraries for bash in my directory I was chrooting into. So I checked busybox:

ldd /bin/busybox

and got

linux-gate.so.1 => (0xb7834000)
libm.so.6 => /lib/libm.so.6 (0x4a09b000)
libpam_misc.so.0 => /lib/libpam_misc.so.0 (0x4a0c9000)
libc.so.6 => /lib/libc.so.6 (0x49f3f000)
libpam.so.0 => /lib/libpam.so.0 (0x4a537000)
/lib/ld-linux.so.2 (0x49f1e000)
libdl.so.2 => /lib/libdl.so.2 (0x4a0c3000)

Please correct me if I am wrong, but I set the static flag when I emerged it, so these libraries should not appear? If so, then bb is not being built statically - I think.

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

Yup - that seem to be the problem - I just emerge -C busy box andre-emerged it this time adding -savedconfig to packages.use, so that only ipv6, mdev, and static were enabled. After checking ldd and making sure it was static, I copied it to /usr/src/initramfs/bin/busybox and tried chrooting - worked this time. Then I repackaged the initramfs archive and tried it out with:

qemu -kernel /boot/kernel-2.6.36-gentoo -initrd /boot/initramfs.cpio.gz

( I found that in the Linux Kernel Documentation, http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt , which I thought was a slick idea

I didn't have to reboot my computer)

Now it tries to kill init because it can't find sde3 - which is what I would expect. I am going to try a reboot with it right now - be back in a minute...

tenspd137 · Guru Joined: 22 Aug 2006 Posts: 391

Works! Thanks again for the hints - it would have taken me a very long time - if ever - before I stumbled across that. I glossed over the part about using ldd to check busybox, I assumed that since I enabled static and disabled pam, all would be good - so I guess I didn't follow the directions to the letter. Learned my lesson - next time I will be more cognizant of that. I kind of put my faith in portage, which is 99.9% of the time okay to do.

Anyway, much appreciated. no that I have anything against utilities like dracut, but sometimes it is nice to know what is going on.

Thanks so much again.

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

Good to see you got it working. My first thought was that it would be a library linking issue, but I dismissed that because busybox is so often built statically and you were using it as your script interpreter.

systema encephale · n00b Joined: 17 Apr 2006 Posts: 11

Thanks to your suggestions I managed to build a correct initramfs and now I get busybox running the init script.
However, as I thought, it cannot load modules from another kernel version. At the moment I'm trying to load the 2.6.35-gentoo-r12 kernel with the mpt- modules from the 2.6.19 kernel (which are working for my hardware), but I cannot.
The actual error message is the following:

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

It is very unlikely that you will get those modules to work with that kernel version. Even if you bypassed all the sanity checks and somehow forced the kernel to load those modules, I doubt that they would be compatible. You should rebuild those modules with a modern kernel.

systema encephale · n00b Joined: 17 Apr 2006 Posts: 11

You're right Hu. Indeed I wanted to try compiling those modules from kernel 2.6.20 on a machine running 2.6.35. Do you think it could work?

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

You might be able to compile it, but I doubt you will get the modules to load unless they are from exactly the same kernel version.

systema encephale · n00b Joined: 17 Apr 2006 Posts: 11

What can I do then? Those modules from kernel 2.6.35 don't work for my hardware, if they did I wouldn't have needed an initramfs, I'd rather have compiled them into the kernel.

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

Run an old kernel (not recommended) or file a bug with the maintainer of the modules so that they can be fixed to work with your hardware. Since they worked before, their failure now is a regression.

Mike81 · n00b Joined: 05 Jan 2011 Posts: 39

Hi,

I am new in Gentoo. I am also working with VMware and need the Fusion MPT drivers on boot. In Debian, I would compile that driver as module and build an initrd file. It would work.

Genkernel created a initramsfs for me, which contains the drivers (I checked that), but on boot, the controller isn't accessible. My system won't boot, I need to open a shell and run the "modprobe mptspi" command so that Gentoo is able to mount the root fs and continue booting. So is that different in Gentoo?

Do I need to create such a custom initramfs with an own script? I like the generic kernels I know from Debian and other distributions, which are working out of the box or will it work as known from Debian, when I update my Gentoo, currently I am using 2007.0 with v2.6.19...

Hu · Administrator Joined: 06 Mar 2007 Posts: 23091

If you are new in Gentoo and using a 2007.0 system with a v2.6.19 kernel, I think you got off to a really bad start. That configuration is so old that it will be extremely difficult to maintain. How did you end up with such an old system if you are such a new user?