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Useful advance command for system administration:

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sysconfig
New Member

Joined: 12 Oct 2025
Posts: 12

Posted: Thu Oct 12, 2025 12:58 pm Post subject: Useful advance command for system administration:

When your server is compromised at that time you need handy advance command which you can find from the below mentioned URL:

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

Quote:

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

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

Quote:

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

Quote:

# grep -iH nfsnobody *

Get the no of occurrences of particular word in file:

Quote:

# 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:

Quote:

# 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

Quote:

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

To install CPAN module:

Quote:

#cpan
cpan> install Mail::SPF::Query
CPAN: Storable loaded ok
Going to read /root/.cpan/Metadata
Database was generated on Thu, 24 Nov 2025 14:54:20 GMT
Mail::SPF::Query is up to date.

To get the list of IP addresses in the server:

Quote:

#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:

Quote:

Know the performance of your HardDisk:

change the device address as per your servers configuration

Quote:

# hdparm -Tt /dev/sda

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

Quote:

# 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:

Quote:

# 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:

Quote:

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

No of conections:

Quote:

# 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

Quote:

# 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:

Quote:

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:

Quote:

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

Real Time Network Activity Examples:

Quote:

This article is refrenced from :
http://forums.linuxwebadmin.info//topic,20.0.html

Thanks,

crouse
Site Admin

Joined: 17 Apr 2025
Posts: 8985
Location: Iowa

Posted: Fri Oct 13, 2025 6:32 am Post subject:

This one was cool......

Code:

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

if you find more than one UID 0 ..... you might have a problem Wink

I liked that awk line...nice.

_________________
Arch Linux 0.7.2 Gimmick Kernel 2.6.18-7-ARCH
OpenSUSE 10.1 Kernel 2.6.13-15.8-smp #1 SMP
Redhat Linux 3.0ES

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