Linux 5.9 Dropping Soft Scrollback Support From FB + VGA Console Code

[Tomin]

I think I may be sometimes using this as I have an ancient Rage 128 VR on my homeserver just to have a display output when I happen to need it (no PCIe slot free). Maybe I should find something more modern for that anyway... Also not too big of deal as I can usually just pipe stuff to less.

[Old Grouch]

Is anyone using less?
I mean for example dmesg | less will give me a scrollable output of the dmesg command

Was I using Linux wrong all this time? Should I have used some obscure functionality of Linux kernel instead?

My implementation* of dmesg allows

$ sudo dmesg -H ; or
$ sudo dmesg --human

which gives 'human-readable' output (pretty colours!) combined with the 'less' interface you know. The first thing I tend to do isissue the command '-i', which makes the searches case insensitive.

so instead of dmesg | less, you can use dmesg -H. You are free to choose.

* output of $ dmesg --version is

dmesg from util-linux 2.31.1

[Old Grouch]

For people needing a quick-n-dirty method of looking at the kernel log messages scrolling rapidly by on boot, the kernel boot parameter 'boot_delay' can be useful.

Setting boot_delay=1000 forces a delay of 1000 ms between each kernel log message, slowing down the output considerably, allowing you to use 'scroll lock'*. Other techniques are available, such as using a serial console. You might need a smaller value.

This was helpful for me when the filesystem driver for the filesystem on which I had my root had a bug in it that caused kernel crashes on trying to mount the root filesystem in the boot process.

You may also wish to have boot options 'noquiet' and 'nosplash', and possible increase the size of the kernel ring buffer with the parameter 'log_buf_len'. In my case, I set it to log_buf_len=16M

Having a camera ready to record the output can be useful as well.

Note, if you are not trying to get more information on gnarly boot problems from the console, then there are almost certainly better methods of capturing and reviewing the output. The number of people who actually need this capability is probably quite small, but non-zero.

*Which is where being able to use Shift-PgUp and Shift-PgDn to view output can be useful, which is the capability that is being removed**.

**There is more about the framebuffer console scrollback here (including how to make the scrollback buffer larger): https://linuxgazette.net/143/anonymous.html . I recommend reading the fbcon.txt documentation.

[Paradigm Shifter]

$ sudo dmesg -H ; or
$ sudo dmesg --human

Thanks, learn something new every day.

[Guest]

IMHO mainline Linux is in urgent need of DRM/KMS based kernel console such as kmscon, however that one is for userspace and pretty much abandoned, I hope systemd would come up with something one day. Linux should have some sort of BSOD like functionality, the console should be able to break 256 glyph barrier and display unicode, it is 2020.

No "soft scrollback"? Well that absolutely sucks. Linux kernel console should have come with tmux like tiling functionality built-in so you could run 2 commands side by side, and copy/paste/pipe between them with a cursor.

Seems like they are always removing the useful parts. I remember the sarcastic patch once posted to lkml that removed i8042 keyboard and display support.

Well the purpose of the kernel is to abstract hardware resources and regulate how userspace uses it. I think trying to cram too much other code into the kernel is a bad idea. Some things are better left to userspace, where they can be written in more modern languages, easily tested, and debugged.

[Guest]

Wtf? I need that functionality every time an nVidia driver update partially-fails, and I have to peer through the log to figure out what went wrong!

Serious Linus, you need to pick a lane for your software -- desktop/laptop with appropriate, maintained scheduler, or barebones server/hypervisor.

If it's failing that often, you should really just ditch NVIDIA.........or stick with an LTS kernel.

[Guest]

I use less all the time. Its use of regex makes searching for things very easy, and the use of arrow keys or page up/down is nice too. I find less to be a really convenient way to read dmesg and log files.

less has regex support?! And here I've been doing normal plain-text searches all this time...............

[Raka555]

Well the purpose of the kernel is to abstract hardware resources and regulate how userspace uses it. I think trying to cram too much other code into the kernel is a bad idea. Some things are better left to userspace, where they can be written in more modern languages, easily tested, and debugged.

when you say modern languages, I hear slow and bloated ...

[Raka555]

Weston is a Wayland compositor, not a display manager or a display server. It does have a GUI with a panel, a clock and you can put some icons on the panel by configuring the weston.ini configuration file.

Basically icewm with lots of missing functionality ...

[StarterX4]

Hell no.