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if I want to boot from old or rescue kernel, how to list

asked 2018-12-24 13:30:34 -0600

nicklevinson gravatar image

Bootup used to list old kernels and I think a rescue kernel. No more. How do I get the list back?

Fedora 29, kept evergreen. Terminal rpm -qa kernel lists 3 kernels but booting into a nondefault is not a normal option any more. I think the problem has existed ever since I installed F29 and had updated the kernel at least once through the Software app.

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answered 2019-01-10 14:23:21 -0600

nicklevinson gravatar image

Hiding the menu was deliberate and is a new functionality. To unhide the menu, open a terminal and type:

sudo grub2-editenv - unset menu_auto_hide

For more information, see https://fedoraproject.org/wiki/Changes/HiddenGrubMenu, which, in turn, refers to https://hansdegoede.livejournal.com/19081.html.

It happens that I ran the above line twice before rebooting, but I doubt running it twice instead of just once made any difference. During the reboot, the list of kernels appeared and selectability of a kernel was apparent. Then I booted into the default kernel. Arguably, I should have done more for a proper test, but, as it is, I think the test was successful.

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answered 2018-12-24 20:14:09 -0600

updated 2018-12-28 21:01:56 -0600

The reason for fixing the kernel is to prevent kernel panic problems even if the kernel is updated. I have seen too many problems in Linux as well as in other systems. It tests whether the kernel is applied when checking the equipment, and applies the upper kernel when it operates stably. Because the server usually runs without a monitor, booting issues due to kernel problems can be seen as one of the server management issues.

I think that it is better to fix the stable kernel because the update problem that does not fix the kernel constantly occurs, but if it is the management device, it may be used to check the kernel and check the kernel status of the monitorless server .

A. The kernel list resides in /boot, and you can adjust the boot order by modifying the /boot/grub2/grub.cfg file.

 [root@nalkal ~]# cd /boot/grub2
 [root@nalkal grub2]#  grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2

 Fedora (4.19.10-300.fc29.x86_64) 29 (Twenty Nine)
 Fedora (0-rescue-6e9b16bbfccc45fe9a0d78c24b9bb694) 29 (Twenty Nine)

B. At the initial boot, you can select the kernel via grub. and default boot kernel set and check default kernel

[root@nalkal grub2]# grub2-set-default "Fedora (4.19.10-300.fc29.x86_64) 29 (Twenty Nine)"

[root@nalkal grub2]# grub2-editenv list
saved_entry=Fedora (4.19.10-300.fc29.x86_64) 29 (Twenty Nine)
boot_success=0
boot_indeterminate=0

C. If you want to exclude the problem from booting the kernel panic, or fix a specific kernel, you can modify /etc/default/grub and /boot/grub2/grub.cfg to apply it.

Happy New Year!!...Have a great day..written by simmon

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Unless I misunderstand, this lets me change the order, but I only want to display the kernel list in a boot screen (not in a post-boot terminal), in case I want to select a kernel for booting on one occasion or another, while on all other occasions booting the default kernel. I assume F29 turned the list display off, maybe accidentally; how do I turn it back on? (Happy holidays, too.)

nicklevinson gravatar imagenicklevinson ( 2018-12-26 12:45:36 -0600 )edit

This answer shows the kernel boot list and allows you to specify a default kernel. And, I told the environment file to change the kernel settings that are displayed at boot time. I will update the answers when detailed questions are added.

simmon gravatar imagesimmon ( 2018-12-26 19:47:40 -0600 )edit

You're still getting a boot list but I no longer am, so something's wrong. The *.cfg has no "print" and I don't know if "show" applies. Requiring that we boot then change the boot order then reboot if the default kernel (usually the newest) is defective may prevent getting to where we can change the boot order. The boot screen in newer F29, at least for me, does not. This loss looks like a bug, so I may report the loss as a bug. Thank you for the list edit procedure.

nicklevinson gravatar imagenicklevinson ( 2018-12-28 20:36:48 -0600 )edit
nicklevinson gravatar imagenicklevinson ( 2019-01-08 19:45:09 -0600 )edit

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Asked: 2018-12-24 13:30:34 -0600

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Last updated: Jan 10