I am trying to dump vmcore to its default target location /var/crash.

If the 'path' line is removed from the kdump configuration, 
the system enters continuous boot loop and only the 'kexec-dmesg.log' file is generated in the kdump target location.


# ll /var/crash/ | wc -l
50    >>>

# ll /var/crash/ | tail
~~~
drwxr-xr-x. 2 root root 29 May 30 21:49 127.0.0.1-2025-05-30-21:49:38
drwxr-xr-x. 2 root root 29 May 30 21:49 127.0.0.1-2025-05-30-21:49:50 drwxr-xr-x. 2 root root 29 May 30 21:50 127.0.0.1-2025-05-30-21:50:03
drwxr-xr-x. 2 root root 29 May 30 21:50 127.0.0.1-2025-05-30-21:50:15
drwxr-xr-x. 2 root root 29 May 30 21:50 127.0.0.1-2025-05-30-21:50:28
drwxr-xr-x. 2 root root 29 May 30 21:50 127.0.0.1-2025-05-30-21:50:41
drwxr-xr-x. 2 root root 29 May 30 21:50 127.0.0.1-2025-05-30-21:50:53
drwxr-xr-x. 2 root root 29 May 30 21:51 127.0.0.1-2025-05-30-21:51:06
drwxr-xr-x. 2 root root 29 May 30 21:51 127.0.0.1-2025-05-30-21:51:19
drwxr-xr-x. 2 root root 29 May 30 21:51 127.0.0.1-2025-05-30-21:51:58
~~~

# ll /var/crash/127.0.0.1-2025-05-30-21\:51\:58/
~~~
total 76
-rw-------. 1 root root 77437 May 30 21:51 kexec-dmesg.log
~~~

# rpm -qa | egrep "kexec|kdump-utils|makedumpfile"
~~~
kdump-utils-1.0.51-10.el10_0.x86_64       Sun May 18 20:57:48 2025
kexec-tools-2.0.29-2.el10.x86_64          Sun May 18 20:57:48 2025
makedumpfile-1.7.6-4.el10.x86_64          Sun May 18 20:57:28 2025
~~~

# uname -r
~~~
Linux rhel10 6.12.0-55.9.1.el10_0.x86_64 #1 SMP PREEMPT_DYNAMIC Tue Mar 25 09:14:09 EDT 2025 x86_64 GNU/Linux
~~~

1. Check if kdump is installed - 
# rpm -q kexec-tools kdump-utils makedumpfile

2. If the kdump is not installed, install required packages - 
# dnf install kexec-tools kdump-utils makedumpfile

3. Set the crashkernel parameter and reboot server.

4. Remove the 'path' from kdump.conf file -
~~~
# grep -v "#" /etc/kdump.conf 
auto_reset_crashkernel yes
core_collector makedumpfile -l --message-level 7 -d 31
~~~

5. Restart kdump service 
~~~
# systemctl restart kdump.service 
# systemctl status -l kdump.service 
~~~

6. Enable and Trigger SysRq 
~~~
# sysctl -a | grep sysrq 
kernel.sysrq = 1
 
# echo c > /proc/sysrq-trigger
~~~

If path is missing from kdump configuration, Kdump should save the vmcore to the default location at '/var/crash'. 
This behavior works as expected in RHEL 9. 

Kdump is unable to generate a vmcore and shows the following errors.
Serial Console Logs -
~~~
[    3.231632] systemd[1]: Starting kdump-capture.service - Kdump Vmcore Save Service...
[    3.297875] kdump.sh[630]: kdump: saving to /sysroot/var/crash/127.0.0.1-2025-05-30-21:43:50/
[    3.300061] kdump.sh[630]: kdump: Remounting the dump target in rw mode.
[    3.303677] kdump.sh[630]: kdump: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2025-05-30-21:43:50/
[    3.306471] kdump.sh[683]: Cannot open /proc/vmcore: No such file or directory
[    3.307849] kdump.sh[630]: kdump: saving vmcore-dmesg.txt failed
[    3.308753] kdump.sh[630]: kdump: saving vmcore
[    3.312975] kdump.sh[685]: open_dump_memory: Can't open the dump memory(/proc/vmcore). No such file or directory
[    3.314133] kdump.sh[630]: kdump: saving vmcore failed, exitcode:1
[    3.314873] kdump.sh[630]: kdump: saving vmcore failed
[    3.315513] kdump.sh[685]: makedumpfile Failed.
[    3.325684] kdump.sh[630]: kdump: saving the /run/initramfs/kexec-dmesg.log to /sysroot/var/crash/127.0.0.1-2025-05-30-21:43:50///
[FAILED] Failed to start kdump-capture.service - Kdump Vmcore Save Service.
[    3.328091] systemd[1]: kdump-capture.service: Main process exited, code=exited, status=1/FAILURE
[    3.330247] systemd[1]: kdump-capture.service: Failed with result 'exit-code'.
[    3.332063] systemd[1]: Failed to start kdump-capture.service - Kdump Vmcore Save Service.
[    3.333259] systemd[1]: kdump-capture.service: Triggering OnFailure= dependencies.

[...]

[    3.357979] systemd[1]: Stopped systemd-tmpfiles-setup.service - Create System Files and Directories.
[    3.358352] systemd[1]: Stopped target local-fs.target - Local File Systems.
kdump: Executing failure action systemctl reboot -f
[    3.390521] systemd[1]: Reboot requested from client PID 703 ('systemctl') (unit emergency.service)...
[    3.390888] systemd[1]: Shutting down.
kdump: Executing final action systemctl reboot -f
Failed to connect to system scope bus via local transport: Connection refused
[    3.461997] systemd-shutdown[1]: Could not detach loopback /dev/loop0: Device or resource busy
[    3.462090] systemd-shutdown[1]: Unable to finalize remaining loop devices, ignoring.
[    3.478635] reboot: Restarting system
[    1.172195] systemd-fstab-generator[267]: Failed to create unit file '/run/systemd/generator/sysroot.mount', as it already exists. Duplicate entry in '/etc/fstab'?
[    1.197880] (sd-e[264]: /usr/lib/systemd/system-generators/systemd-fstab-generator failed with exit status 1.
[    1.246774] systemd-modules-load[298]: Module 'msr' is built in
~~~

kexec-dmesg.log - 
# less var/crash/127.0.0.1-2025-05-30-21\:51\:58/kexec-dmesg.log
~~~
May 30 21:51:58 rhel10 systemd[1]: dracut-mount.service - dracut mount hook was skipped because no trigger condition checks were met.
May 30 21:51:58 rhel10 systemd[1]: Starting dracut-pre-pivot.service - dracut pre-pivot and cleanup hook...
May 30 21:51:58 rhel10 systemd[1]: Finished dracut-pre-pivot.service - dracut pre-pivot and cleanup hook.
May 30 21:51:58 rhel10 systemd[1]: Starting kdump-capture.service - Kdump Vmcore Save Service...
May 30 21:51:58 rhel10 kdump.sh[629]: kdump: saving to /sysroot/var/crash/127.0.0.1-2025-05-30-21:51:58/
May 30 21:51:58 rhel10 kdump.sh[629]: kdump: Remounting the dump target in rw mode.
May 30 21:51:58 rhel10 kdump.sh[629]: kdump: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2025-05-30-21:51:58/
May 30 21:51:58 rhel10 kdump.sh[682]: Cannot open /proc/vmcore: No such file or directory
May 30 21:51:58 rhel10 kdump.sh[629]: kdump: saving vmcore-dmesg.txt failed
May 30 21:51:58 rhel10 kdump.sh[629]: kdump: saving vmcore
May 30 21:51:58 rhel10 kdump.sh[684]: open_dump_memory: Can't open the dump memory(/proc/vmcore). No such file or directory
May 30 21:51:58 rhel10 kdump.sh[629]: kdump: saving vmcore failed, exitcode:1
May 30 21:51:58 rhel10 kdump.sh[629]: kdump: saving vmcore failed
May 30 21:51:58 rhel10 kdump.sh[684]: makedumpfile Failed.
~~~