I'm running Ubuntu 20.04.2 LTS on a Dell Inc. Precision T3610/09M8Y8 and my linux version is 5.8.0-44-generic. I have been successfully compiling and installing the Linux net-next kernel for a few months now. However, now whenever I install a kernel compiled with make olddefconfig, I get the following error:

Loading Linux 5.11.0+ ...
Loading initial ramdisk ...
error: out of memory.

Booting into safe mode reveals the following

0.602008] VFS: Cannot open root device ''UUID=311542e2-03db-45a0-aa79-991341cb3708'' or unknown-block(0,0); error -6
0.602840] Please append a correct, ''root='' boot option: here are the available partitions:
0.603646] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
0.604488] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.11.0+ #3
0.605314] Hardware name: Dell Inc. Precision T3610/09M8Y8, BIOS A07 04/29/2014
0.606155] Call Trace:
0.606837]   dump_stack+0x7d/0x9c
0.606837]   panic=0x101/0x2e3
0.606837]   mount_block_root+0x299/0x31d
0.606837]   mount_root+0x6a/0x6d
0.606837]   prepare_namespace+0x13f/0x170
0.606837]   kernel_init_freeable+0x23a/0x260
0.606837]   ? rest_init+0xba/0xba
0.606837]   kernel_init+0xe/0x116
0.606837]   ret_from_fork+0x22/0x30
0.606837] Kernel Offset: 0x11c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
0.606837] ---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ] ---

I've looked at the other kernels that run successfully in GRUB, and they all have the same set root='hd0,gpt2' as the kernels I'm trying to boot into and failing.

I've looked at other posts such as https://askubuntu.com/questions/41930/kernel-panic-not-syncing-vfs-unable-to-mount-root-fs-on-unknown-block0-0/ and not syncing: VFS: Unable to mount root fs on unknown-block(0,0) but neither of those solved my issue. The solutions involved running some variation of the following commands:

dpkg --configure -a
update initramfs -u

I think the issue is the machine cannot find the initramfs for the compiled kernels, because when I installed kernel 5.11.0-051100-generic from .deb using dpkg, everything worked fine. I've also tried copying the .config file over from the 5.11 kernel, to no success. I was able to successfully compile and run kernels a few weeks ago, so I don't know why every compiled kernel fails now.

How do I fix this issue? Is there a way to update the initramfs for a custom kernel (I am trying to install the linux net-next branch, but have also tried the generic linux 5.11.0+ branch and received the same error)?

1 Answer 1


I installed Ubuntu version 18.04.5 LTS and was able to boot into a compiled kernel. It seems to be an issue that occurred when I updated Ubuntu 20.04.2

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