Linux basic commands to start as a system administration part 1
Copy a remote file (using - Concatenation operator)
ssh abc@sysloggerserver1.linuxnix.com: /var/ftp/pub/webadmin/debian/read abc@sysloggerserver2.persistent.co.in:/opt/oradba/debadmin/logic/abc/
'&&' –Logical AND operator
execute second command, if the first command runs successfully
ping -c1 abc.com && ssh abc@abc.com
example: Check if a folder exists or not. If it's not present, create it
[ ! -d /var/temp ] && mkdir /var/temp
Example: Create folder, if the folder creation is successful, then only change the directory.
mkdir abc && cd abc
|| –Logical OR operator
Example: Create a folder if the folder does not exits.
[ -d /var/temp ] || mkdir /var/temp
Example: Ping to a machine and let users know if it's not reachable in a meaning full way.
ping -c1 google.com &> /dev/null || echo “There is some problem with network, please connect your network admin"
&& and || operator use case
Example: Check if a file exists or not. If it exists inform user it exists otherwise create it.
[-f /var/temp.txt] && echo "file exist" || touch /var/temp.txt
Example:Check if my previous command executed successfully or not pwd /home/surendra
[ $? -eq 0 ] && echo "Yes, $? command successfully executed" || echo “pwd command failed"
| — PIPE operator
output of first command as an input to second command
Example: Count no of files/folder located in a folder
ls -l | wc -l
Example: Display all the partition names in the system.
df -m | awk '{print $1}' // -m is to check space in MB
Example: to count no of partitions:
df |wc -l
! -NOT operator (Negation operator)
Example:Remove all the files, which are not a .doc file.
ls | grep -v doc | xargs rm -rf or rm -rf *.{xls, txt, pdf}
better way to achieve this: rm !(*.doc)
Example: Move all the files expect .doc files to /opt
mv !(*.doc) /opt/
{ } –Command combination operator
combine two or more commands to be executed depending on the previous command
Example: Check if /opt/temp.txt exists or not?
[-f /opt/temp.txt] && echo "file exits" || {"The file does not exist"; touch /opt/temp.txt}
() –Precedence operator
execute command in precedence order
( caommand1 && command2 ) || ( command3 && command4 )
Service is running or not in Linux
Method 1: Using service command
$service servicename status
Method 2: Using init.d scripts which are located in /etc/init.d folder
/etc/init.d/cron status
List file with soft link
ls -lrt | grep ^l // ^ character is a special regular expression which means start of line
find . -type l
find . -maxdepth 1 -type l
Count occurrence of a word
$ grep -c "Error" logfile.txt
Printing lines before and after of matching word
$ grep --context=6 error logfile.txt or grep -C 6 "Error" logfile.txt
Pattern using egrep and regular expression
$ egrep 'Error|Exception' logfile.txt
Search patterns in gzip files using zgrep
$ zgrep -i Error *.gz
Search whole word in a file using grep
$grep -W Error logfile.txt
More control, use `\<' and `\>' to match the start and end of words
$ grep 'ERROR>' *
Display files names which contains given word
$ grep -l ERROR *.log
Option to display lines numbers
$ grep -n ERROR logfile.txt
ssh abc@sysloggerserver1.linuxnix.com: /var/ftp/pub/webadmin/debian/read abc@sysloggerserver2.persistent.co.in:/opt/oradba/debadmin/logic/abc/
'&&' –Logical AND operator
execute second command, if the first command runs successfully
ping -c1 abc.com && ssh abc@abc.com
example: Check if a folder exists or not. If it's not present, create it
[ ! -d /var/temp ] && mkdir /var/temp
Example: Create folder, if the folder creation is successful, then only change the directory.
mkdir abc && cd abc
|| –Logical OR operator
Example: Create a folder if the folder does not exits.
[ -d /var/temp ] || mkdir /var/temp
Example: Ping to a machine and let users know if it's not reachable in a meaning full way.
ping -c1 google.com &> /dev/null || echo “There is some problem with network, please connect your network admin"
&& and || operator use case
Example: Check if a file exists or not. If it exists inform user it exists otherwise create it.
[-f /var/temp.txt] && echo "file exist" || touch /var/temp.txt
Example:Check if my previous command executed successfully or not pwd /home/surendra
[ $? -eq 0 ] && echo "Yes, $? command successfully executed" || echo “pwd command failed"
| — PIPE operator
output of first command as an input to second command
Example: Count no of files/folder located in a folder
ls -l | wc -l
Example: Display all the partition names in the system.
df -m | awk '{print $1}' // -m is to check space in MB
Example: to count no of partitions:
df |wc -l
! -NOT operator (Negation operator)
Example:Remove all the files, which are not a .doc file.
ls | grep -v doc | xargs rm -rf or rm -rf *.{xls, txt, pdf}
better way to achieve this: rm !(*.doc)
Example: Move all the files expect .doc files to /opt
mv !(*.doc) /opt/
{ } –Command combination operator
combine two or more commands to be executed depending on the previous command
Example: Check if /opt/temp.txt exists or not?
[-f /opt/temp.txt] && echo "file exits" || {"The file does not exist"; touch /opt/temp.txt}
() –Precedence operator
execute command in precedence order
( caommand1 && command2 ) || ( command3 && command4 )
Service is running or not in Linux
Method 1: Using service command
$service servicename status
Method 2: Using init.d scripts which are located in /etc/init.d folder
/etc/init.d/cron status
List file with soft link
ls -lrt | grep ^l // ^ character is a special regular expression which means start of line
find . -type l
find . -maxdepth 1 -type l
Count occurrence of a word
$ grep -c "Error" logfile.txt
Printing lines before and after of matching word
$ grep --context=6 error logfile.txt or grep -C 6 "Error" logfile.txt
Pattern using egrep and regular expression
$ egrep 'Error|Exception' logfile.txt
Search patterns in gzip files using zgrep
$ zgrep -i Error *.gz
Search whole word in a file using grep
$grep -W Error logfile.txt
More control, use `\<' and `\>' to match the start and end of words
$ grep 'ERROR>' *
Display files names which contains given word
$ grep -l ERROR *.log
Option to display lines numbers
$ grep -n ERROR logfile.txt