How to configure kdump to save vmcore on remote server via ssh

Issue

How to configure kdump to save vmcore on a remote server via SSH.

Environment

• CloudLinux

Solution

To do so, follow the next steps:

1. Prepare RSA key pair for kdump

# cp /root/.ssh/id_rsa /root/.ssh/kdump_id_rsa

Then add the public RSA key to your dump machine where the dump will be stored and test the connectivity with SSH.

2. Configure kdump. Update your /etc/kdump.conf so it looks like this

sshkey /root/.ssh/kdump_id_rsa
ssh root@<ip(domain)_of_the_dump_machine>
core_collector makedumpfile -F -l --message-level 1 -d 31
force_rebuild 1

Other parameters should be commented on.

Update /etc/sysconfig/kdump with MKDUMPRD_ARGS="--builtin=libafs"

3. Restart kdump

# systemctl restart kdump

Then you can delete force_rebuild 1 from the /etc/kdump.conf.

4. Test, if possible

If you have some test environment, it'd be great to test if all works as expected by crashing the test machine with:

echo c > /proc/sysrq-trigger

Secondly, we would like to ask the client to turn on debug logs in one of the affected servers:

sysctl kernel.printk=7

After all steps above are applied, we should wait for the issue to occur and see if we get a dump/debug logs.