I seem to have a System76 kernel on a non-System76 workstation

[watchpocket]

As the title suggests, I've discovered that the Linux kernel I'm using on my (non-System76) desktop workstation is a System76-built kernel:

$ uname -sr
Linux 5.4.0-7642-generic

The current version of the (non-System76) 5.4.0 kernel is 5.4.0-92-generic.
(Though it looks like it will be upgrading to something newer soon, as kernel security updates are apparently being rolled out right now.)

Kernel version 5.4.0-7642 doesn't exist anywhere in the Ubuntu kernels builds.

The closest I can find about kernel 5.4.0-7642 is this: https://launchpad.net/~system76/+arc...build/19851655 (https://launchpad.net/~system76/+archive/ubuntu/proposed/+build/19851655)
Which is a System76-built kernel. (And also very old by the looks of it.)

I did recently have a System76 "Wild Dog" desktop computer dating from 2010. I pulled this SSD from that computer not long ago and put it into a new computer. This must be where this "leftover" kernel is from (even though I re-formatted the drive and fresh-installed 20.04 Linux-MATE.

My questions:

Does it make sense to keep the 5.4.0-7642 System76 kernel on a non-System76 machine?
Could there be hazards to doing so?
What kernel would it make sense for me to move to, or upgrade to?

I'm running the Ubuntu-MATE 20.04.3 LTS OS.

[&KyT$0P#]

my (non-System76) desktop workstation

What is your current desktop workstation?


Does it make sense to keep the 5.4.0-7642 System76 kernel on a non-System76 machine?

No. That kernel is old and maybe now insecure. Better to use a current kernel version.


Could there be hazards to doing so?

Security wise, I don't know. Stability wise, if you don't notice any issue there probably isn't one.

I use System76 kernels in a VirtualBox VM and it works fine.


What kernel would it make sense for me to move to, or upgrade to?

You have 3 options:

1) "Downgrade" to the stock 5.4.x kernel from the Ubuntu repositories.

2) Upgrade to the standard Ubuntu HWE kernel (currently 5.13.x I think).

3) Upgrade to the latest System76 kernel (currently 5.15.11).

If it were me, and if the 5.4.x kernels don't have issues on your current hardware, I'd probably go with (1) to maximize stability. Some programs need to build kernel modules (for example VirtualBox, proprietary Nvidia drivers, v4l2loopback) and so can potentially break with newer kernel series. If you don't have any programs like that, any of the kernel options would probably be fine.

[guiverc]

I'd check your sources as you may have added a Pop OS source into your system & thus introduced other non-Ubuntu packages beyond what you initially wanted.

I'd like see if you have a source for it with `apt-cache policy` and then `sudo apt update` and read the output looking for anything unusual added by user(s) with `sudo` rights (or if it's only you, maybe it'll trigger your memory). I may search apt logs looking for when it was installed (it may also show what else was installed), may consider using `ubuntu-security-status --thirdparty` to explore what else maybe non-Ubuntu etc...

(FYI: I consider Ubuntu-MATE as Ubuntu; thus I'd not expect to find any System76 packages on my Ubuntu/Xubuntu/Lubuntu/Ubuntu-MATE system [my system is bloated with multiple DEs installed])

[watchpocket]

What is your current desktop workstation?

If you need any info about it beyond what's in my sig, let me know.
I built it myself a few months ago. (I had a long wait to be able to buy a graphics card, btw, and finally got one via NewEgg auction.)


. . . That kernel is old and maybe now insecure. Better to use a current kernel version.

I'll either go with the stock 5.4 current version (5.4.0-92), or 5.13 HWE.
(I was using 5.11 on another drive but USB audio didn't work in 5.11.)

I'm guessing 5.13 should be stable and beyond an experimental period.


. . . Some programs need to build kernel modules (for example . . .proprietary Nvidia drivers [ my emphasis -watchpocket ]. . . ) and so can potentially break with newer kernel series. If you don't have any programs like that, any of the kernel options would probably be fine.

I do have proprietary Nvidia drivers, and I recently tried to update a batch of nvidia libraries, etc.
I allowed these updates to come in on my 5.4.0-7642 20.04 drive, and also on another drive running the 5.11 kernel with the same 20.04 UbuntuMATE OS.

After those updates came in, I couldn't get past the login screen on either OS. (I used Timeshift to revert back to a previous state.)

So I think I may be leaning toward using the 5.4.0-92 kernel for stability.
I'm guessing I can do that with this command:

sudo apt install --install-recommends linux-generic

(I am also still a bit curious about how 5.13 might work, and if it's stable enough. I may try 5.4 on one drive and 5.13 on the other.)

[&KyT$0P#]

I'm guessing I can do that with this command:

sudo apt install --install-recommends linux-generic

It's unlikely to be that simple. Please post the outputs from the following commands -

apt-cache policy
apt-cache policy linux-generic linux-image-generic linux-system76

[watchpocket]

I'd check your sources as you may have added a Pop OS source into your system & thus introduced other non-Ubuntu packages beyond what you initially wanted.

I don't think you'll find a Pop OS source or anything else System76-related in my sources. I try to keep a close eye on them.
(At the moment I'm using a fairly long list of PPAs -- 27 of them.)

Nevertheless, you can look at the output of `apt-cache policy`; `sudo apt update` and `ubuntu-security-status --thirdparty` here (https://paste.ubuntu.com/p/V2NQTnzRgC/).



and read the output looking for anything unusual added by user(s) with `sudo` rights

I'm the only user.


I may search apt logs looking for when it was installed (it may also show what else was installed)

Interesting: /var/log/apt/term.log.5 indeed shows that the System76 5.4.0-7642-generic kernel was installed in October 2020.
It may have presented itself as a routine kernel upgrade, except I didn't know it was a specialized System76 kernel.

[watchpocket]

It's unlikely to be that simple.

Here, btw, is what sudo apt-get install --install-recommends linux-generic returned:


Reading package lists... Done
Building dependency tree
Reading state information... Done
linux-generic is already the newest version (5.4.0.7642.46~1598628707~20.04~040157c~dev).
0 upgraded, 0 newly installed, 0 to remove and 19 not upgraded.



And here is what sudo apt-get install --install-recommends linux-generic-hwe-20.04 returned:

Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
linux-headers-5.11.0-46-generic linux-headers-generic-hwe-20.04 linux-hwe-5.11-headers-5.11.0-46 linux-image-5.11.0-46-generic linux-image-generic-hwe-20.04
linux-modules-5.11.0-46-generic linux-modules-extra-5.11.0-46-generic
Suggested packages:
fdutils linux-doc | linux-hwe-5.11-source-5.11.0 linux-hwe-5.11-tools
The following NEW packages will be installed:
linux-generic-hwe-20.04 linux-headers-5.11.0-46-generic linux-headers-generic-hwe-20.04 linux-hwe-5.11-headers-5.11.0-46 linux-image-5.11.0-46-generic linux-image-generic-hwe-20.04
linux-modules-5.11.0-46-generic linux-modules-extra-5.11.0-46-generic
0 upgraded, 8 newly installed, 0 to remove and 19 not upgraded.
Need to get 93.0 MB of archives.
After this operation, 494 MB of additional disk space will be used.
Do you want to continue? [Y/n] n



Please post the outputs from the following commands -

apt-cache policy
This can be found here (https://paste.ubuntu.com/p/V2NQTnzRgC/).



apt-cache policy linux-generic linux-image-generic linux-system76


--> apt-cache policy linux-generic linux-image-generic linux-system76 pts/2 Saturday 2022-01-15 18:33:00
linux-generic:
Installed: 5.4.0.7642.46~1598628707~20.04~040157c~dev
Candidate: 5.4.0.7642.46~1598628707~20.04~040157c~dev
Version table:
*** 5.4.0.7642.46~1598628707~20.04~040157c~dev 100
100 /var/lib/dpkg/status
5.4.0.94.98 500
500 http://mirror.us-ny2.kamatera.com/ubuntu focal-updates/main amd64 Packages
5.4.0.92.96 500
500 http://mirror.us-ny2.kamatera.com/ubuntu focal-security/main amd64 Packages
5.4.0.26.32 500
500 http://mirror.us-ny2.kamatera.com/ubuntu focal/main amd64 Packages
linux-image-generic:
Installed: 5.4.0.7642.46~1598628707~20.04~040157c~dev
Candidate: 5.4.0.7642.46~1598628707~20.04~040157c~dev
Version table:
*** 5.4.0.7642.46~1598628707~20.04~040157c~dev 100
100 /var/lib/dpkg/status
5.4.0.94.98 500
500 http://mirror.us-ny2.kamatera.com/ubuntu focal-updates/main amd64 Packages
5.4.0.92.96 500
500 http://mirror.us-ny2.kamatera.com/ubuntu focal-security/main amd64 Packages
5.4.0.26.32 500
500 http://mirror.us-ny2.kamatera.com/ubuntu focal/main amd64 Packages
linux-system76:
Installed: (none)
Candidate: (none)
Version table:

[&KyT$0P#]

Thanks. Try the following (note that you can replace sudo apt-get with apt-get -s to check what it would do before actually going ahead):

1) Make sure the 5.4.0-94-generic kernel is installed -

sudo apt-get install linux-{headers,modules-extra}-5.4.0-94-generic

2) Reboot, pulling up the GRUB menu and ensure you boot into the 5.4.0-94-generic kernel.

3) Downgrade the kernel meta-packages (and linux-libc-dev if you have it installed) -

sudo apt-get install linux-generic/focal linux-{headers,image}-generic/focal linux-libc-dev/focal

4) Mark kernel packages from (1) as automatically installed -

sudo apt-mark auto linux-{headers,modules-extra}-5.4.0-94-generic

5) Confirm that things are normal: the following command should not try to autoremove the kernel you just installed -

apt-get -s --purge autoremove

6) If all is well at this point, it should be safe to purge the System76 kernel.

7) Check which kernel GRUB boots by default, it should now be the 5.4.0-94-generic.

[watchpocket]

Thanks. Try the following (note that you can replace sudo apt-get with apt-get -s to check what it would do before actually going ahead):

1) Make sure the 5.4.0-94-generic kernel is installed -

sudo apt-get install linux-{headers,modules-extra}-5.4.0-94-generic


Having so far gone only this far, kernel 5.4.0-94 appearsto be installed. However, at the bottom of everything returned after entering the above command, this appeared:



DKMS: install completed.
...done.
Setting up linux-image-5.4.0-94-generic (5.4.0-94.106) ...
Failed to create symlink to vmlinuz-5.4.0-94-generic: Operation not permitted at /usr/bin/linux-update-symlinks line 64.
dpkg: error processing package linux-image-5.4.0-94-generic (--configure):
installed linux-image-5.4.0-94-generic package post-installation script subprocess returned error exit status 1
dpkg: dependency problems prevent configuration of linux-modules-extra-5.4.0-94-generic:
linux-modules-extra-5.4.0-94-generic depends on linux-image-5.4.0-94-generic | linux-image-unsigned-5.4.0-94-generic; however:
Package linux-image-5.4.0-94-generic is not configured yet.
Package linux-image-unsigned-5.4.0-94-generic is not installed.

dpkg: error processing package linux-modules-extra-5.4.0-94-generic (--configure):
dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
Errors were encountered while processing:
linux-image-5.4.0-94-generic
linux-modules-extra-5.4.0-94-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)
sudo apt-get install linux-{headers,modules-extra}-5.4.0-94-generic 131.39s user 15.12s system 221% cpu 1:06.28 total


Here is line 64 (and surrounding lines) of /usr/bin/linux-update-symlinks:


59
60 # Create a symlink with a temporary name
61 my $rand;
62 while (($rand = int(rand(1000000))) && !symlink($source, "$dest.$rand")) {
63 *.......if ($! != POSIX::EEXIST) {
64 *....... die "Failed to create symlink to $source: $!";
65 *.......}
66 }
67
68 # Move it into place atomically
69 if (!rename("$dest.$rand", $dest)) {

How significant are these error messages, and what might be done to remedy them? Thanks.

[&KyT$0P#]

Failed to create symlink to vmlinuz-5.4.0-94-generic: Operation not permitted at /usr/bin/linux-update-symlinks line 64.

I'm not sure which symlink that is exactly, but check the output of

ls -la /
ls -la /boot
findmnt
make sure that user root can write to & create symlinks in both / and /boot

[watchpocket]

See below:



-> ls -la / pts/3 Sunday 2022-01-16 16:57:28
total 88
4 drwxr-xr-x 21 root root 4096 Sep 30 12:00 ./
4 drwxr-xr-x 21 root root 4096 Sep 30 12:00 ../
0 lrwxrwxrwx 1 root root 7 Oct 13 2020 bin -> usr/bin/
4 drwxr-xr-x 4 root root 4096 Dec 31 1969 boot/
4 drwxr-xr-x 2 root root 4096 Oct 13 2020 cdrom/
0 drwxr-xr-x 20 root root 4860 Jan 16 15:48 dev/
12 drwxr-xr-x 176 root root 12288 Jan 16 14:48 etc/
4 drwxr-xr-x 3 root root 4096 Oct 13 2020 home/
0 lrwxrwxrwx 1 root root 7 Oct 13 2020 lib -> usr/lib/
0 lrwxrwxrwx 1 root root 9 Oct 13 2020 lib32 -> usr/lib32/
0 lrwxrwxrwx 1 root root 9 Oct 13 2020 lib64 -> usr/lib64/
0 lrwxrwxrwx 1 root root 10 Oct 13 2020 libx32 -> usr/libx32/
4 drwx------ 2 root root 4096 Jan 11 13:56 lost+found/
4 drwxr-xr-x 4 root root 4096 Dec 15 18:00 media/
4 drwxr-xr-x 4 root root 4096 Jan 2 17:01 mnt/
4 drwxr-xr-x 8 root root 4096 Jan 16 14:48 opt/
0 dr-xr-xr-x 408 root root 0 Jan 16 15:08 proc/
4 drwxr-xr-x 8 root root 4096 Jan 2 15:30 root/
0 drwxr-xr-x 43 root root 1300 Jan 16 16:04 run/
0 lrwxrwxrwx 1 root root 8 Oct 13 2020 sbin -> usr/sbin/
4 drwxrwxr-x 16 root root 4096 Dec 30 18:17 snap/
4 drwxr-xr-x 2 root root 4096 Jul 31 2020 srv/
0 dr-xr-xr-x 13 root root 0 Jan 16 15:36 sys/
4 drwxr-xr-x 9 root root 4096 Jan 16 14:00 timeshift/
16 drwxrwxrwt 17 root root 16384 Jan 16 17:00 tmp/
4 drwxr-xr-x 14 root root 4096 Jul 31 2020 usr/
4 drwxr-xr-x 14 root root 4096 Jul 31 2020 var/
[rj@rjbox-2:~] [zsh-5.8] 2004 --> pts/3 Sunday 2022-01-16 17:02:00
[rj@rjbox-2:~] [zsh-5.8] 2004 --> pts/3 Sunday 2022-01-16 17:02:03
[rj@rjbox-2:~] [zsh-5.8] 2004 --> ls -la /boot pts/3 Sunday 2022-01-16 17:02:03
total 18240
4 drwxr-xr-x 4 root root 4096 Dec 31 1969 ./
4 drwxr-xr-x 21 root root 4096 Sep 30 12:00 ../
4 drwxr-xr-x 4 root root 4096 Dec 31 1969 EFI/
4648 -rwxr-xr-x 1 root root 4756293 Jan 6 16:56 System.map-5.4.0-94-generic*
236 -rwxr-xr-x 1 root root 237940 Jan 6 16:56 config-5.4.0-94-generic*
4 drwxr-xr-x 4 root root 4096 Jan 11 14:43 grub/
13340 -rwxr-xr-x 1 root root 13656320 Jan 6 18:07 vmlinuz-5.4.0-94-generic*
[rj@rjbox-2:~] [zsh-5.8] 2005 --> pts/3 Sunday 2022-01-16 17:02:13
[rj@rjbox-2:~] [zsh-5.8] 2005 --> findmnt pts/3 Sunday 2022-01-16 17:02:25
TARGET SOURCE FSTYPE OPTIONS
/ /dev/sda2 ext4 rw,relatime,errors=remount-ro,stripe=8191
├─/sys sysfs sysfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/kernel/security securityfs securityfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/fs/cgroup tmpfs tmpfs ro,nosuid,nodev,noexec,mode=755
│ │ ├─/sys/fs/cgroup/unified cgroup2 cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate
│ │ ├─/sys/fs/cgroup/systemd cgroup cgroup rw,nosuid,nodev,noexec,relatime,xattr,name=systemd
│ │ ├─/sys/fs/cgroup/devices cgroup cgroup rw,nosuid,nodev,noexec,relatime,devices
│ │ ├─/sys/fs/cgroup/pids cgroup cgroup rw,nosuid,nodev,noexec,relatime,pids
│ │ ├─/sys/fs/cgroup/cpuset cgroup cgroup rw,nosuid,nodev,noexec,relatime,cpuset
│ │ ├─/sys/fs/cgroup/net_cls,net_prio cgroup cgroup rw,nosuid,nodev,noexec,relatime,net_cls,net_prio
│ │ ├─/sys/fs/cgroup/cpu,cpuacct cgroup cgroup rw,nosuid,nodev,noexec,relatime,cpu,cpuacct
│ │ ├─/sys/fs/cgroup/blkio cgroup cgroup rw,nosuid,nodev,noexec,relatime,blkio
│ │ ├─/sys/fs/cgroup/perf_event cgroup cgroup rw,nosuid,nodev,noexec,relatime,perf_event
│ │ ├─/sys/fs/cgroup/hugetlb cgroup cgroup rw,nosuid,nodev,noexec,relatime,hugetlb
│ │ ├─/sys/fs/cgroup/memory cgroup cgroup rw,nosuid,nodev,noexec,relatime,memory
│ │ ├─/sys/fs/cgroup/rdma cgroup cgroup rw,nosuid,nodev,noexec,relatime,rdma
│ │ └─/sys/fs/cgroup/freezer cgroup cgroup rw,nosuid,nodev,noexec,relatime,freezer
│ ├─/sys/fs/pstore pstore pstore rw,nosuid,nodev,noexec,relatime
│ ├─/sys/firmware/efi/efivars efivarfs efivarfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/fs/bpf none bpf rw,nosuid,nodev,noexec,relatime,mode=700
│ ├─/sys/kernel/debug debugfs debugfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/kernel/tracing tracefs tracefs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/fs/fuse/connections fusectl fusectl rw,nosuid,nodev,noexec,relatime
│ └─/sys/kernel/config configfs configfs rw,nosuid,nodev,noexec,relatime
├─/proc proc proc rw,nosuid,nodev,noexec,relatime
│ ├─/proc/sys/fs/binfmt_misc systemd-1 autofs rw,relatime,fd=28,pgrp=1,timeout=0,minproto=5,maxp roto=5,direct,pipe_ino=29322
│ │ └─/proc/sys/fs/binfmt_misc binfmt_misc binfmt_misc rw,nosuid,nodev,noexec,relatime
│ └─/proc/fs/nfsd nfsd nfsd rw,relatime
├─/dev udev devtmpfs rw,nosuid,noexec,relatime,size=65841208k,nr_inodes =16460302,mode=755
│ ├─/dev/pts devpts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode= 000
│ ├─/dev/shm tmpfs tmpfs rw,nosuid,nodev
│ ├─/dev/mqueue mqueue mqueue rw,nosuid,nodev,noexec,relatime
│ └─/dev/hugepages hugetlbfs hugetlbfs rw,relatime,pagesize=2M
├─/run tmpfs tmpfs rw,nosuid,nodev,noexec,relatime,size=13189572k,mod e=755
│ ├─/run/lock tmpfs tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k
│ ├─/run/rpc_pipefs sunrpc rpc_pipefs rw,relatime
│ ├─/run/user/1000 tmpfs tmpfs rw,nosuid,nodev,relatime,size=13189568k,mode=700,u id=1000,gid=1000
│ │ ├─/run/user/1000/gvfs gvfsd-fuse fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=1000,group_id=100 0
│ │ └─/run/user/1000/doc portal fuse.portal rw,nosuid,nodev,relatime,user_id=1000,group_id=100 0
│ ├─/run/timeshift/backup /dev/sdc2 ext4 rw,relatime,stripe=8191
│ └─/run/snapd/ns tmpfs[/snapd/ns] tmpfs rw,nosuid,nodev,noexec,relatime,size=13189572k,mod e=755
│ └─/run/snapd/ns/keepassxc.mnt nsfs[mnt:[4026533361]] nsfs rw
├─/snap/brave/140 /dev/loop1 squashfs ro,nodev,relatime
├─/snap/core20/1270 /dev/loop4 squashfs ro,nodev,relatime
├─/snap/bare/5 /dev/loop0 squashfs ro,nodev,relatime
├─/snap/youtube-dl-pro/53 /dev/loop6 squashfs ro,nodev,relatime
├─/snap/pyqt5-runtime/11 /dev/loop7 squashfs ro,nodev,relatime
├─/boot /dev/sda1 vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,ioc harset=iso8859-1,shortname=mixed,errors=remount-ro
│ └─/boot/efi /dev/sda1 vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,ioc harset=iso8859-1,shortname=mixed,errors=remount-ro
├─/snap/keepassxc/1522 /dev/loop5 squashfs ro,nodev,relatime
├─/snap/youtube-dl-pro/52 /dev/loop9 squashfs ro,nodev,relatime
├─/snap/pyqt5-runtime/12 /dev/loop8 squashfs ro,nodev,relatime
├─/snap/ubuntu-mate-welcome/639 /dev/loop10 squashfs ro,nodev,relatime
├─/snap/gtk-common-themes/1519 /dev/loop11 squashfs ro,nodev,relatime
├─/snap/snapd/14295 /dev/loop13 squashfs ro,nodev,relatime
├─/snap/lnav/2198 /dev/loop12 squashfs ro,nodev,relatime
├─/snap/kde-frameworks-5-qt-5-15-core20/14 /dev/loop14 squashfs ro,nodev,relatime
├─/snap/ubuntu-mate-welcome/646 /dev/loop15 squashfs ro,nodev,relatime
├─/snap/brave/141 /dev/loop16 squashfs ro,nodev,relatime
├─/snap/snapd/14066 /dev/loop17 squashfs ro,nodev,relatime
├─/snap/core18/2253 /dev/loop18 squashfs ro,nodev,relatime
├─/snap/software-boutique/54 /dev/loop19 squashfs ro,nodev,relatime
├─/snap/core18/2284 /dev/loop2 squashfs ro,nodev,relatime
└─/snap/core20/1242 /dev/loop3 squashfs ro,nodev,relatime

[watchpocket]

I am wondering if the "lib32" and "libx32" lines should be there. I don't think I've seen them there previously:

0 lrwxrwxrwx 1 root root 9 Oct 13 2020 lib32 -> usr/lib32/

[&KyT$0P#]

The problem is that your EFI partition somehow got mounted at /boot as well as the normal location /boot/efi at the same time. But /boot needs to be a Linux type filesystem. Sorry I have no idea how to safely fix this :(

[watchpocket]

OK - Thanks loads for helping me get this far.
(It may be that my less-than-perfect use of Timeshift had something to do with the misplacement of the EFI partition.)


--> lf /boot
total 18232
4 drwxr-xr-x 4 root root 4096 Dec 31 1969 EFI/
4648 -rwxr-xr-x 1 root root 4756293 Jan 6 16:56 System.map-5.4.0-94-generic*
236 -rwxr-xr-x 1 root root 237940 Jan 6 16:56 config-5.4.0-94-generic*
4 drwxr-xr-x 4 root root 4096 Jan 11 14:43 grub/
13340 -rwxr-xr-x 1 root root 13656320 Jan 6 18:07 vmlinuz-5.4.0-94-generic*
[rj@rjbox-2:~] [zsh-5.8] 2007 --> lf /boot/EFI
total 18232
4 drwxr-xr-x 4 root root 4096 Jan 11 14:43 EFI/
4648 -rwxr-xr-x 1 root root 4756293 Jan 6 16:56 System.map-5.4.0-94-generic*
236 -rwxr-xr-x 1 root root 237940 Jan 6 16:56 config-5.4.0-94-generic*
4 drwxr-xr-x 4 root root 4096 Jan 11 14:43 grub/
13340 -rwxr-xr-x 1 root root 13656320 Jan 6 18:07 vmlinuz-5.4.0-94-generic*

--> lf /boot/EFI/EFI
total 8
4 drwxr-xr-x 2 root root 4096 Jan 11 14:43 BOOT/
4 drwxr-xr-x 2 root root 4096 Jan 11 14:43 ubuntu/

--> lf /boot/EFI/EFI/BOOT
total 1860
936 -rwxr-xr-x 1 root root 955656 Jan 11 14:43 BOOTX64.EFI*
84 -rwxr-xr-x 1 root root 85672 Jan 11 14:43 fbx64.efi*
840 -rwxr-xr-x 1 root root 856232 Jan 11 14:43 mmx64.efi*

[watchpocket]

1) Make sure the 5.4.0-94-generic kernel is installed -

sudo apt-get install linux-{headers,modules-extra}-5.4.0-94-generic
[etc]

Just a note to say that all of this worked fine on my other (NVMe) drive, where I was also running the 5.4.0-7642 kernel.
I'm now using 5.4.0-94-generic there and have removed the System76 kernel. (There were no issues with the /boot and /boot/efi dirs there.)

Now all I need to do is get grub to have the sda drive as an entry on its menu, and of course, to fix my sda drive's /boot dir.

[&KyT$0P#]

Just a note to say that all of this worked fine on my other (NVMe) drive, where I was also running the 5.4.0-7642 kernel.
I'm now using 5.4.0-94-generic there and have removed the System76 kernel.

Cool, you're welcome & thanks for reporting back :KS

[watchpocket]

I've now cleaned up my /boot and /boot/efi dirs on my sda drive, and I've installed kernel 5.4.0-94-generic there as well as on my NVMe drive.

I've completely rid myself of the 5.4.0-7642 System76 kernel on both of my drives. (For anyone new to this thread, I'm not using any System76 hardware.)

There are still a few nits to work out, but for purposes of this thread, I've marked it SOLVED. Thanks again, Halogen2.