Most Helpful and Frequently used Linux Commands

getconf LONG_BIT

ctags

CPU information and Memory Information
cat /proc/cpuinfo
cat /proc/meminfo

Open ports and associated processes/services
netstat -anp (on Windows netstat -anb)
lsof command can also be used to do same work

Search for files only which contains log string in file from root directory recursively
find / -name log -type f  *
Search for directories only which contains log string in directory from current directory recursively  and move the found directory to /tmp directory
find . -name log -type d  * | xargs cp /tmp/

perl command to generate buffer

Name of the Operating System
lsb_release -a

Knowing 32-bit or 64bit Operating System
getconf LONG_BIT

Linux Kernel details
uname -a



ps -aef
ngrep
lsof