Unix/Linux command reference (2)

System info

• date : show the current date and time 
• cal : show this month's calendar
• uptime : show current uptime
• w : display who is online
• whoami :  who you are logged in as
• finger user : display information about user
• uname -a : show kernel information
• cat /proc/cpuinfo : cpu information
• cat /proc/meninfo : memory information
• man command :  show the manual for command
• df : show disk usage
• du : show directory space usage
• free : show memory and swap usage
• whereis app : show possible locations of app
• which app :  show which app will be run by default

Compression

• tar cf file.tar files : create a tar named file.tar containing files
• tar xf file.tar : extract the files from file.tar
• tar czf file.tar.gz files : create a tar with Gzip compression
• tar xzf file.tar.gz : extract a tar using Gzip
• tar cjf file.tar.bz2 : create a tar with Bzip2 compression
• tar xjf file.tar.bz2 : extract a tar using Bzip2
• gzip file : compresses file and renames it to file.gz
• gzip -d file.gz :  decompresses file.gz back to file

Network

• ping host :  ping host and output results
• whois domain : get whois information for domain
• dig domain : get DNS information for domain
• dig -x host : reverse lookup host 
• wget file : download file
• wget -c file : continue a stopped download

Installation

• Install from source : ./configure
• make
• make install
• dpkg -i pkg.deb : install a package (Debian)
• rpm -Uvh pkg.rpm : install a package (RPM)