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My 10 most used linux commands

Hans-Henry Jakobsen — Mon, 25 Feb 2008 07:49:40 +0000

This is a oneliner bash command to determine my 10 most used linux commands according to my history file

history | awk '{CMD[$2]++;count++;}END { for (a in CMD)print CMD[a] " " CMD[a]/count*100 "% " a;}' | grep -v "./" | column -c3 -s " " -t | sort -nr | nl |  head -n10

The result

     1  188  37.6%  vi
     2  38   7.6%   ls
     3  24   4.8%   cat
     4  22   4.4%   apt-get
     5  12   2.4%   date
     6  11   2.2%   tail
     7  11   2.2%   cd
     8  10   2%     rm
     9  10   2%     man
    10  9    1.8%   basename

It looks like i use vim a lot on my home server. You should try it yourself and see what commands you use the most.

Source: http://linux.byexamples.com

Allow NFS through iptables

Hans-Henry Jakobsen — Thu, 20 Dec 2007 09:50:41 +0000

This is one way to determine the ports needed to open in your iptables rules to get NFS to work properly. First we need to determine the ports NFS uses

rpcinfo -p | awk -F " " '{print $3 ", " $4 ", " $5}' | sort | uniq

Notice!
Since portmap assigns ports on random this example is only valid as long as you don’t restart your NFS.

On my system, a RedHat Enterprise Linux WS 4, the result was

proto, port,
tcp, 111, portmapper
tcp, 2049, nfs
tcp, 32771, nlockmgr
tcp, 768, rquotad
tcp, 782, mountd
udp, 111, portmapper
udp, 2049, nfs
udp, 32768, nlockmgr
udp, 765, rquotad
udp, 779, mountd

This gave me a nice overview of protocols (tcp/udp) and ports used.

Now the rules

iptables -A RH-Firewall-1-INPUT -s 192.168.0.0/255.255.255.0 -i eth0 -p tcp -m state --state NEW -m multiport --dports 111,2049,32771,768,782 -j ACCEPT
iptables -A RH-Firewall-1-INPUT -s 192.168.0.0/255.255.255.0 -i eth0 -p udp -m state --state NEW -m multiport --dports 111,2049,32768,765,779 -j ACCEPT

You see that the multiport statement is just like the result of my rpcinfo command above.

Remember to save your new rules, othervise they will disappear the next time the iptables rules are being loaded.

In addition to this rule you should add the iptables rule for ssh access I wrote about earlier.

Another way to determine the ports

nmap -sC -p 111 localhost

Notice!
This solution won’t work after a reboot of the server since NFS changes ports. One way to overcome this problem is to follow the instructions in a newer post I’ve made about RedHat and NFS.

Query RPM database/packages and list their architecture

Hans-Henry Jakobsen — Mon, 26 Nov 2007 13:07:11 +0000

If you use the –queryformat argument with rpm it is possible to query RPMs for different architectures installed
# rpm -qa --queryformat %{NAME}-%{VERSION}-%{ARCH}\\n | grep dbus-glib | sort

Result
dbus-glib-0.22-12.EL.5-i386 dbus-glib-0.22-12.EL.5-x86_64

This can also be used in one of my previous posts: Remove duplicate packages when querying the rpm database.

Sort IP address

Hans-Henry Jakobsen — Mon, 12 Nov 2007 09:56:47 +0000

Sorting IP addresses using sort is not easy because the dot confuses sort.
This line makes it possible to sort by the whole value of the address

sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4 ipaddresses.txt

You can also sort by the last octet

sort -r. -n +3.0 ipaddresses.txt

List processes in a hierarchy

Hans-Henry Jakobsen — Sat, 09 Jun 2007 00:04:32 +0000

ps -e -o pid,args --forest

List processes by % cpu usage

ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'

List processes by mem usage

ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS

List info for particular process IDs

ps -p 1,2