If panic() is called twice (from the disk sync routines, for example) the system is rebooted without syncing the disks.
dumpdev (str) Indicates the device (usually a swap partition) to which a crash dump should be written in the event of a system crash. If the value of this variable is "AUTO", the first suitable swap device listed in /etc/fstab will be used as dump device. Otherwise, the value of this variable is passed as the argument to dumpon(8). To disable crash dumps, set this variable to "NO". dumpon_flags (str) Flags to pass to dumpon(8) when configuring dumpdev as the system dump device. dumpdir (str) When the system reboots after a crash and a crash dump is found on the device specified by the dumpdev variable, savecore(8) will save that crash dump and a copy of the kernel to the directory specified by the dumpdir variable. The default value is /var/crash. Set to "NO" to not run savecore(8) at boot time when dumpdir is set.
# Set dumpdev to "AUTO" to enable crash dumps, "NO" to disable dumpdev="AUTO"
Have you thought about setting up a remote syslog server to capture the logs? Even if a crash would wipe the whole filesystem the remote syslog would still have the logs.But we have a strang behaviour after the crash, every log in /var/log vanished from the disk (after rebooting, very 1st log was dated from 10 43 am from every type of log, messages, auth.log, mount.today ....).
dmesg -aand check if there are any error messages related to the crash.
dumpon -lthe currently configured dump device(s).
savecore -f /dev/external-device( -f forcing a dump), you can check if a kernel dump is written on the specified location as expected .