Advance command for System Administrator

[sysconfig]

[Strat with Linux || Optimize, Secure and increase performance of Apache || Already Started]

To get the list of username with its user ID in formatted way:

# awk -F":" '{ print "username: " $1 "\t\tuid:" $3 }' /etc/passwd

Find the particular string from the list of files in current directory:

# cd /etc
# for i in $(find -type f); do grep -iH nfsnobody $i; done

Or

# grep -iH nfsnobody *

Get the no of occurrences of particular word in file:

# awk '/ServerName/ {i=i+1} END {print i}' /etc/httpd/conf/httpd.conf
# grep ServerName /etc/httpd/conf/httpd.conf

To delete resources of semaphore arrays from memory:

# ipcs -s | grep apache | perl -e 'while (<STDIN>) { @a=split(/\s+/); print`ipcrm sem $a[1]`}'

To check whether perl module is installed correctly or not:
 
If all is correct then output of this command nothing

# perl -e 'require Mail::SPF::Query'

To install CPAN module:

#cpan
 cpan> install Mail::SPF::Query
 CPAN: Storable loaded ok
 Going to read /root/.cpan/Metadata
 Database was generated on Thu, 24 Nov 2005 14:54:20 GMT
 Mail::SPF::Query is up to date.

To get the list of IP addresses in the server:

#ifconfig | grep -vw inet6 | grep -w inet | cut -d : -f 2 | cut -d \  -f 1

Find list of IP address along with eth device and network mask:

# ifconfig | cut -d " " -f1,12,16 | grep -A 1 eth | tr -d - | tr -s "\n" |sed -e :a -e N -e 's/\n/ /'

Know the performance of your HardDisk:

change the device address as per your servers configuration

# hdparm -Tt /dev/sda   

Get the customized output of raw accesslog of httpd:
Navigate the folder where your http access log reside

# tail -f access_log | awk '{if ($11 ~"\"-\"") print $1, $7, $12; else print $1, $10, $11, $12}'

The details of the present http connections can be found by using:

# netstat -plan | grep ":80 " | awk {'print $5'} |awk -F: {'print $1'}|sort
# cat /proc/net/ip_conntrack | grep "port=80" | wc -l

Number of connection from perticular IP addfess:

# netstat -ntu | awk '{print $5}'| cut -d: -f1 | sort | uniq -c | sort -nr | more

No of conections:

# netstat -alntp

#/sbin/ldconfig /usr/local/lib   - Update the system linker cache

Port scanning using nmap:
You can customized it to get more informative output

# nmap -sS localhost  -

instead host localhost, it could be IP address of another server which is in question

You can execute bash command a certain number of times by using something similar to the following:

   

n=0;while test -$n -gt -10; do echo n=$n; n=$[$n+1]; done

That code will print "n=0", "n=1", and so on 10 times.

Only get the listing of directories:

ls -F $1 | grep \/ | sed -e 's/\/$/4/g'

Real Time Network Activity Examples:

root# watch -d "netstat -nalp |grep -v DGRAM |grep -v STREAM |grep -v LISTEN"
root# watch "netstat -nalp"|grep ":TCP PORT Number"
root# watch "netstat -nalp"|grep ":22"

Good collection. However, we can create any command according to our requiremnt by concatinating with other commands.

I think below command will be use to know the highest process used by IP address for particular services

netstat -tnp | awk -F':|/|\t*| *' '{if( $7 == "25" ) {print; $cmd=sprintf("ps -uwwwp %d",$9);system($cmd);}}'

thanks

[sysconfig]

[Strat with Linux || Optimize, Secure and increase performance of Apache || Already Started]

Return which ports are currently being listened :

netstat -ant | grep LISTEN | sed -n 's/^[^:]*:\([0-9]\+\) .*$/\1/p'

[mits]

I think below command will be use to know the highest process used by IP address for particular services

netstat -tnp | awk -F':|/|\t*| *' '{if( $7 == "25" ) {print; $cmd=sprintf("ps -uwwwp %d",$9);system($cmd);}}'

thanks

Please note that you will have process ID of only connection when it is in ESTABLISED stat, so you need to grep the output the netstat , I think below mentioned command will work:

netstat -tnp |grep EST |  awk -F':|/|\t*| *' '{if( $8 == "21" ) {print; $cmd=sprintf("ps uwwwp %d",$15);system($cmd);}}'

cheers

I think you should also check the below mentioned URL:

http://forums.linuxwebadmin.info/index.php/topic,35.0.html

thanx

[sysconfig]

[Strat with Linux || Optimize, Secure and increase performance of Apache || Already Started]

Hello,

Please check the useful guide on how to find files and directories using different search criteria at:

http://forums.linuxwebadmin.info/index.php/topic,35.0.html

If you want to know more about rpm packages, how to install it, check it queries it, at;

http://forums.linuxwebadmin.info/index.php/topic,41.0.html

thanx

[netstat -tupl]

   
netstat -tupl   :List internet services on a system

netstat -tup     :List active connections to/from system
 
# lsof -p $$    :List paths that process id has open

# lsof ~   :List processes that have specified path open

# last reboot   :Show system reboot history.

# ls -lSr   :Show files, biggest last

# du -s * | sort -k1,1rn | head    :Show top disk users in current dir. See also dutop

# cat /proc/partitions   :Show all partitions registered on the system