[johnnym]

This is for all people still operating a Cobalt 5000 series machine - well, that's most likely me and perhaps @Titox , but who knows?

I recently updated my Debian Buster based NFS root FS and matching kernel (4.19.249) for my RaQ XTR. No patches are needed for 4.19.x for the Cobalt 5000 series, though there's no support for the display AFAIK.

I'm currently preparing a collection of compressed root FS and matching kernel (plus kernel config if you want do build it yourself or make changes). Everything is configured for diskless operation and can be downloaded from a website showing the required directory structure for operation:

PHP Code:

/
├── nfsroot-x86 -> /srv/nfs/cobalt/nfsroot-x86
├── srv/
│   └── nfs/
│       ├── cobalt/
│       │   └── nfsroot-x86/
│       │       ├── vmlinux.bz2 -> vmlinux.bz2-4.19.249-cobalt5000
│       │       ├── vmlinux.bz2-4.19.249-cobalt5000
│       │       └── .config-4.19.249-cobalt5000
│       └── raq-xtr/
│           ├── root -> root-buster
│           ├── root-buster
│           └── root-buster.tar.xz
└── tftpboot -> /srv/nfs/cobalt/nfsroot-x86 


PM me if you're interested in running that on your Cobalt 5000, I'll then send you the URL for the downloads.

I don't know if this could not also be transformed for on-disk operation, but you first would need to build a kernel with on-disk FS support compiled into the kernel. Currently this is only available as module to save space and there's no support for an initramfs AFAIK. I can assist with that if there's demand, though I never used my RaQ XTR with disks as I am missing the sleds.

Be advised, I could only test this on a RaQ XTR, as I don't have any other Cobalt 5000 series machines. If you're having a RaQ 550, please let me know if it works for you, too. Also notice that sometimes - though relatively seldom in my case - the kernel crashes during boot-up for an unknown reason. Usually after a reboot the identical kernel boots through w/o an issue. From my past experience, I haven't seen any crashes after the kernel successfully booted.

Kernel building

1. To build a kernel you basically have to install "linux-source" inside of the RaQ's FS and unpack the Linux source code tarball in "/usr/src/". For building I usually use a more modern x86_64 machine, from which I chroot into the RaQ's FS (also useful to speed up updating packages).
   
2. Copy the kernel config file into the "/usr/src/linux-source-4.19/" directory as ".config"
   
3. Change to that directory and issue make ARCH=i386 oldconfig and select the desired setting for any new configuration options or issue  make ARCH=i386 olddefconfig instead. ARCH=i386 is only needed if you're running this on a x86_64 machine.
   
4. If you like to change the configuration - e.g. to make the kernel useful for booting from disk instead of the network - use make ARCH=i386 menuconfig for example
   
5. For building I then usually use [time] make ARCH=i386 [-jN] all (with N being the number of hardware threads + 1)
   
6. When finished, the unstripped kernel ("vmlinux") is present in the current directory. First strip it and then compress it with [time] bzip2 -9 -c -z vmlinux > vmlinux.bz2[-4.19.x-cobalt5000]. The maximum size of the kernel is limited by the capabilities of the in-firmware kernel of the Cobalt 5000 system.
   
7. Don't forget to install the kernel modules with make ARCH=i386 modules_install