Get Android Kernel log

 To catch Kernel log, need a rooted Android device and adb shell worable, then use the adb logcat command:

$adb shell logcat -v time -f /dev/kmsg | cat /proc/kmsg

To  write the output to a file:

$adb shell logcat -v time -f /dev/kmsg | cat /proc/kmsg > /sdcard/log.txt