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Reboot into the new kernel and test to see if it works.
Remove `quiet` (enable more log messages) and `rhgb` (disable graphical boot) from the boot flags. If the text output is too fast to read, add `boot_delay=1000` (the number of milliseconds to delay in between printk during boot). You can use a camera to take pictures of the output.
Repeat the previous five steps until you've found the commit that introduced the problem.
Setting `nmi_watchdog=1` on the kernel command line will cause a panic when an NMI watchdog timeout occurs.
Sometimes the kernel fails to boot. Depending on where the problem is in the boot process, there may or may not be any output. Some good first steps are:
Sound issues
Start a new `git-bisect` with `git bisect start`.
The kernel, like any software, has bugs. It's a large, complex project and it can be difficult to troubleshoot problems. This document covers some basic troubleshooting techniques to help narrow down the root cause of an issue.
the light on the keyboard to change state can be used as an indication of whether or not the kernel has hung completely, or if there is something else going on.
The SysRq magic keys may still work. You may need to add `sysrq_always_enabled=1` to the kernel boot command line. See https://fedoraproject.org/wiki/QA/Sysrq[the wiki article on SysRq on usage details].
When reporting an issue with the kernel you should always attach the kernel logs, usually collected with the `dmesg` command. For some types of issues, you may need to collect more logs.
xref:kernel/build-custom-kernel.adoc#_building_the_kernel[Build the kernel]. Sometimes commits cannot be built. If this happens, skip the commit with `git bisect skip`.
xref:kernel/build-custom-kernel.adoc#_installing_the_kernel[Install the kernel].