Wakkadoo Techs Basic UNIX Command Tips

Basic Command Line Tips 

• 32bit or 64bit 
  • Works for every binary, not only java: 
    • file - < $(which java) # heavily bashic 
    • cat `which java` | file - # universal 
    
    
• Cat all non-commented and non-empty lines from file 
  egrep -v '^(#|$)' filename 
  
  
• Create list of ping-able hosts from list of hosts 
  •  for i in `cat all`;do ping -c 2 $i 2>pinglog ; if [ $? != 0 ];  then echo "cant ping $i >> pinglog"; else echo $i >> pingfile; fi; done 

AWK 

• Remove all line breaks from file 
  • awk 'BEGIN{}{printf "%d, ", NR}END{printf "\n"}' filename 

• Add up numbers in a file 
  • cat numberlist | awk '{total = total +$1}END{print total}' 

Bash Prompt 

• $ PS1="[\u@\h:\w ] $ " 
  • put in .bashrc if ya want /etc/skel 

   

• Run 'unalias' to remove alias 
  • unalias cp 

• Clear bash history 
  •  history -c && rm -f ~/.bash_history 
  
  
• Setup Shell for vi command editing 
  • set -o vi  (place in .bashrc) 

• Set Background Terminal Color 
  • set_color -b blue 
  
  
• ksh file completion 
  • set EDITOR to vi then ESC \ will do file completion. 
  
  

Check if Server is VM? 

•  dmidecode | grep -i product 

        Product Name: VMware Virtual Platform 

CPU Tips 

• Get number of CPU 
  •  grep -i "physical id" /proc/cpuinfo | sort -u | wc -l 
  
  
  • dmidecode |grep -i cpu 
          Socket Designation: CPU1 
          Socket Designation: CPU2 
          Socket Designation: CPU3 
          Socket Designation: CPU4 
                  CPU.Socket.1 
                  CPU.Socket.2 
                  CPU.Socket.3 
                  CPU.Socket.4 
  
  
• Check if HyperThreading is enabled 
  • # of siblings = # of cores 
    • cat /proc/cpuinfo |egrep 'sibling|cores' 
      • 
        
    • grep -i "processor" /proc/cpuinfo | sort -u | wc -l 
    
    

Cut Tips & Sort 

• Cut with space as delimeter 
  • cut -d ' ' -f 1 

• Sort list of IP Address 
  • Cat (or whatever cmd)  iplist | sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4 
  
  
• cut 1st field and show remaining 3 
  •  hostname | cut -d . -f 2,3,4 
  
  
• Sort Files by Size 
  • ls -lh | sort -n -k5,5 

Disk Usage 

• Check size of directory 
  • du -ch directory 
    
    

Email Tips 

• mail -s “Some Subject” you@youremail.com < /opt/app/app.log 

For Loops 

• Sequence Number 
   for i in `seq 1 10`;do 
  > echo $i 
  
  
• Use Seq to go thru 1-5 
  for i in {1..5};do 
  > echo "host-X-$i" 
  > done 
  
  

Grep 

• to stop after the first match.  
  • grep -m 1 
  
  

LDAP 

tcpdump -n tcp port ldap 

IP Address 

• ifconfig eth0 | grep inet |awk  ' {print $2 }'| cut -d ':' -f2 

Iozone Testing 

• iozone -s 1g -r 1024 -i 0 -i 1 -e -t 1 -F f:\IOTest\t1 -b f:\iotest\t1-10.xls Test 1  
• iozone -s 2g -r 1024 -i 0 -i 1 -e -t 1 -F f:\IOTest\t1 -b f:\iotest\test2.xls Test 2  
• iozone -s 2g -r 2048 -i 0 -i 1 -e -t 1 -F f:\IOTest\t1 -b f:\iotest\test3.xls Test 3  
• iozone -s 2g -r 2048 -i 0 -i 1 -e -t 2 -F f:\IOTest\t1 f:\iotest\t2 -b f:\iotest\test4.xls Test 4 Notes: 2 Threads  
• iozone -s 2g -r 2048 -i 0 -i 1 -e -t 4 -F f:\IOTest\t1 f:\iotest\t2 f:\iotest\t3 f:\iotest\t4 -b f:\iotest\test5.xls Test 5 Notes: 4 Threads  
• iozone -s 2g -r 4096 -i 0 -i 1 -e -t 4 -F f:\IOTest\t1 f:\iotest\t2 f:\iotest\t3 f:\iotest\t4 -b f:\iotest\test6.xls Test 6 Notes: 4 Threads  

NIC Info 

To invoke diagnostics from ethtool, enter this command: (will disrupt traffic) 

• ethtool -t <EthX> 

• ethtool -S eth0 

NTP 

• to sync, add ntp server to /etc/ntp.conf 
• service ntpd stop 
• ntpdate -u myntpserver.com 
• date 
• verify it synced 
• restart with 'service ntpd start' 

• check with 'ntpq -p' 

NMAP 

Run nmap to view subnet IP's 

•  nmap -sP 10.48.24.0/22 

PATHS 

  

Add to the beginning of the $PATH environment variable, use the following: 

• PATH=/data/myscripts:$PATH 

To add that directory to the end of the path, use the following command: 

• PATH=$PATH:/data/myscripts 
• 
  

Pause in a script 

• read -p "Press [Enter] key to reboot" 

Process 

• Show extended info 
  • ps awwx 
  
  

RPM & YUM 

  

• Clean up rpm database 
  • rm -rf /var/lib/rpm/_db* 
  • rpm --rebuilddb -vv 
• View dependencies 
  • Rpm -qR package 
  • Rpm -qipR rpmfile 

Routes 

Add default gateway (if router is ip below) 

• # route add default gw 192.168.1.254 eth0 

Rsync 

• Rsync -auvP  (src dir)  (dest dir) 

rsync -avz --exclude-from 'exclude-list.txt' source/ destination/ 

Screen 

To launch screen, type screen and some commnads 

• To disconnect (but leave the session running) 
  • Hit Ctrl + A and then Ctrl + D in immediate succession. You will see the message [detached] 
• To reconnect to an already running session 
  • screen -r 
• To reconnect to an existing session, or create a new one if none exists 
  • screen -D -r 
• To list open screen windows 
• Hit Ctrl + A and then W in immediate succession  
  
  

Sudo

Check Syntax of sudoers

• visudo -c

Tar 

To list contents 

• tar -tvf file.tar  

Tar exlude file/directory 

• tar cvf --exclude 
  
  

Top 

• top, press shift ‘>’ and it will sort by memory used. 

Users 

Show all unique users who last logged in. 

• last | awk '{ print $1 }' |sort |uniq