Linux and Java: Disk usage, Memory check, JVM virtual memory, Processor Info, Kernel Info

Check disk usage:
df -h

Check file size in a directory
du -sh *


Check memory usage, display total memory in MB:
free -t -m


Set JVM virtual memory:
java -jar -Xms128m -Xmx512m bigapp.jar

Processor Info:
cat /proc/cpuinfo

Kernel version:
uname -r