[SOLVED] Kernel huge or generic, which is running?

frushiyama · 01-11-2017, 05:36 AM

Is there a way to know which kernel is running without look at bootloader config files?
I am asking this just to confirm what grub2 does on the advanced options from the boot submenu.

business_kid · 01-11-2017, 06:28 AM

It's logged in dmesg & /var/log/messages. I use lilo, not grub, but either of these work (as root)

Code:

cat /var/log/messages |grep Command
cat /var/log/messages |grep BOOT_IMAGE

You can also view the logs with less

malekmustaq · 01-11-2017, 06:29 AM

Hi,

Usually it is known by using this command:

Code:

uname -a 
or this command
cat /proc/version

If the information given is not convincing enough and you know what modules which kernel is loading you can trace them all using this:

Code:

less /proc/config.gz

The kernel.huge usually is loading more than the generic.

Hope that helps. Good luck.

m.m.

Jjanel · 01-11-2017, 07:20 AM

cat /proc/cmdline
? EDIT: Answer: #10! Thanks! (I learned a bunch here!)
(

Note to NoobSelf: Slack'=='Linux!=grubOS. poweroff that Mint [VBox that's eating halfXPnetbook] &Start some SlackS [which IantiGUI had already installed]

)

Paulo2 · 01-11-2017, 07:47 AM

14.2 generic uname -v

Code:

#1 SMP Sun Dec 11 16:03:41 CST 2016

and huge

Code:

#2 SMP Sun Dec 11 16:18:36 CST 2016

Is generic always built before huge?

GazL · 01-11-2017, 08:18 AM

I'm an advocate of using the LOCALVERSION string when building a kernel to clearly differentiate them, but the stock slackware kernels aren't built that way, so you're basically left looking for clues such as whether ext4 support is built in or not.

zgrep -q 'CONFIG_EXT4_FS=y' /proc/config.gz is likely as good a way as any.

I've no idea what grub does. I consider it to be a monstrosity and avoid it like the plague.

frushiyama · 01-11-2017, 09:55 AM

All approaches depends on LOCALVERSION, except the GazL suggestion that searchs one feature built-in only in the generic kernel.
The command from GazL didn't work here but i got the idea.

kjhambrick · 01-11-2017, 10:12 AM

Thanks GazL !

That's a very clever method you shared.

Not sure why I would ever need to script such info but I've saved the following into my scripts/ directory

Thanks again

-- kjh

Code:

zgrep -q 'CONFIG_EXT4_FS=y' /proc/config.gz && IsGeneric=0 || IsGeneric=1

echo "IsGeneric = $IsGeneric"

business_kid · 01-12-2017, 06:01 AM

@GazL:

Quote:

I've no idea what grub does. I consider it to be a monstrosity and avoid it like the plague.

+1 on that!

Richard Cranium · 01-12-2017, 10:21 PM

Code:

0 ✓ cranium@cranium ~ $ cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-generic-4.4.38 root=UUID=f15cdaf7-c299-4cc0-8a16-533808d59454 ro
0 ✓ cranium@cranium ~ $

That appears to work for me (I'm running grub2 on this machine).

...Ah, one of my machines running grub1 gives a different answer:

Code:

cranium@gateway:~$ cat /proc/cmdline 
ro vga=791 4
cranium@gateway:~$

...I wonder what my machine that's running lilo says?

Code:

cranium@toshiba:~$ cat /proc/cmdline 
BOOT_IMAGE=4.4.38 ro swapaccount=1
cranium@toshiba:~$

Hmm. Only the machine running the horrible grub2 code provides useful output.

chris.willing · 01-12-2017, 11:33 PM

cat /proc/cmdline seems to have the most potential to produce something meaningful. For each grub2 and lilo, the first part of /proc/cmdline's output depends on how grub2/lilo was configured. For grub2, it is whatever the value of the linux field was e.g.

Code:

linux   /boot/vmlinuz-generic-4.4.38 root=/dev/sda7 rootfstype=ext4 raid=noautodetect intel_idle.max_cstate="1" nomodeset ro 4

in my grub.conf file produces:

Code:

chris@d6:~$ cat /proc/cmdline 
BOOT_IMAGE=/boot/vmlinuz-generic-4.4.38 root=/dev/sda7 rootfstype=ext4 raid=noautodetect intel_idle.max_cstate=1 nomodeset ro 4

.

For lilo, the /proc/cmdline output begins with whatever the label field contains e.g.

Code:

label Linux-generic

in my lilo.conf produces

Code:

root@sl64-142-vmbuilder:~# cat /proc/cmdline
BOOT_IMAGE=Linux-generic ro root=802 vt.default_utf8=0

Conclusion: put something meaningful in your grub2/lilo configuration file so that 'cat /proc/cmdline' can tell you what you want to know.

bassmadrigal · 01-13-2017, 01:32 PM

Overall, the problem ends up being... the kernel doesn't have a "generic" or "huge" option. It doesn't understand what they are. Those are just two different configurations that Pat has provided for us. One has the majority of drivers compiled as modules (generic) and the other has the majority of modules compiled in the kernel (huge).

If you end up just using the symlink for your booting (by default, /boot/vmlinuz points to /boot/vmlinuz-huge-4.4.14 on a fresh 14.2 install, and /boot/vmlinuz is what is used in lilo.conf to call the kernel), your /proc/cmdline will provide no useful output since the entry is just called "Linux". The below is taken off a fresh install of 14.2 without modification to the boot system.

Code:

jbhansen@febtober:~$ cat /proc/cmdline 
auto BOOT_IMAGE=Linux ro root=802 vt.default_utf8=1

That provides no useful information. However, when you check /etc/lilo.conf and /boot, you'd realize it points to the huge kernel.

Really, if you're using the stock kernels, the best check is GazL's quick check to see if ext4 is compiled into the kernel. If it is, you know you're running a huge kernel, and if it's compiled as a module, you're running a generic kernel. You can even simplify kjhambrick's little script to a one-liner.

Code:

zgrep -q 'CONFIG_EXT4_FS=y' /proc/config.gz && echo "Huge kernel" || echo "Generic Kernel"

However, that becomes more difficult to determine if you're running a self-compiled kernel. Many people will include the default filesystem (ext4 in most cases) into the kernel to prevent needing to load it in an initrd. At that point, your kernel is neither "Huge" nor "Generic" as those are only official terms applying to official Slackware kernels. I guess your big thing would be to see how much of the kernel is compiled as modules.

I just did a random check, and surprisingly, between the huge and generic kernels, there's only a difference of about 100 modules between the generic and huge kernels. Both kernels contain over 3000 items compiled in as modules. But I guess those 101 items equate to about 3.1MB within the kernel (4.2MB for the 4.4.14 generic and 7.3MB for the huge).

Code:

jbhansen@febtober:~$ fgrep "=m" /boot/config-generic-4.4.14 | wc -l
3408
jbhansen@febtober:~$ fgrep "=m" /boot/config-huge-4.4.14 | wc -l
3307

kjhambrick · 01-13-2017, 02:18 PM

bassmadrigal --

Thank you for an excellent explanation !

-- kjh

GazL · 01-13-2017, 03:03 PM

Bass' is correct. Looking for ext4 is only a quick and dirty clue. If you want more certainty, then you could do something like

Code:

#!/bin/sh

case "$(md5sum /proc/config.gz | cut -f1 -d ' ')" in
  aad7671490f498cdab5799b028fd6ab9)  echo "GazL's Custom x86_64 4.9.3-local kernel" ;;
  *)                                 echo "Unknown kernel" ;;
esac

Add an entry for the md5sum of each kernel it is likely to encounter. Obviously this takes a little extra work as you'll need to collate and maintain the list of md5sums to start with, but it should be a reasonably reliable way of identifying them once that's done.

Richard Cranium · 01-13-2017, 03:11 PM

Quote:

Originally Posted by chris.willing

Conclusion: put something meaningful in your grub2/lilo configuration file so that 'cat /proc/cmdline' can tell you what you want to know.

Well done! Thanks for looking into that.