Create random password using /dev/urandom

In many situation administrators are affronted to generate passwords, however it’s more secure to keep in eyes random password even that ordinarie one.
Well, for such use let’s keep it simple and let’s define some files:

/dev/random: is a special file that serves as a true random number generator or as a pseudorandom number generator.
/dev/urandom: (“unlocked” random source) which reuses the internal pool to produce more pseudo-random bits.

If your system does not have /dev/random and /dev/urandom created already, they can be created with the following commands:
$ mknod -m 644 /dev/random c 1 8
$ mknod -m 644 /dev/urandom c 1 9
$ chown root:root /dev/random /dev/urandom

$ tr -cd a-zA-Z0-9 < /dev/urandom | head -c 12 ; echo ""

Number of public IP address in an AS (example IAM)

You can get the number of public address in an AS by using whois and ipcalc tools like this query :

$ for ip in $(whois -i origin AS6713 | awk ‘/route/ { print $2 }’); do ipcalc $ip; done | awk ‘/\/Net/{ ip+=$2 } END { printf ip “\n” }’

155638

Pipes in syslog

Using syslog, there are a possiblity to write the output to a pipe, so we can read this pipe from a program. But we have to be careful, syslogd should not wedge but we will have missing and/or mangled
messages if they arrive faster than our program can process them.
Let’s take look to how to create these pipes and read from them:

First create a named pipe using mkfifo:
$ mkfifo -p /home/mezgani/syslog.pipe

Make syslog.conf to points to this file:
*.info |/home/mezgani/syslog.pipe

Restart syslog:
$ sudo pkill -HUP syslogd

Create processing script that read the pipe
$ cat > foo
#!/bin/bash
cat /home/mezgani/syslog.pipe | while read input
do
# some stuff
echo ${input}
# ….
done

cpan recent modules

This command grabs and print the URL of a plain text file that lists new files added to CPAN the past two weeks.
$ perl -MLWP::Simple -e “getprint ‘http://cpan.org/RECENT’”

You can easily make it part of a tidy little shell command, like this one that mails you the list of new SOAP::modules
$ perl -MLWP::Simple -e “getprint ‘http://cpan.org/RECENT’” | grep “/by-module/SOAP” | mail -s “New SOAP module! ” $USER

Using bash variables in awk

First you need to assign the variables with the -v option:
The option -v followed by var=value is an assignment to be done before (the awk program).

Example of use:
This example define a bash file, that look for any entry “address” into the squid’s access file.

$ cat > search
#!/bin/bash
awk -v address=”$1″ ‘$3 == address && $4 ~ /200/’ /var/log/squid/access.log

$ chmod +x search; sudo ./search 192.168.0.2

The top 10 of your most used unix commands

This tips show you the ten most used unix commands.
Do the following on your console and see what you’re frequently using:

$ history|awk ‘{print $2}’|awk ‘BEGIN {FS=”|”} {print $1}’|sort|uniq -c|sort -rn|head -10

mkdir and cd

Many times, i find myself making and moving to a directory quite a bit, normally I use something like this
$ mkdir ~/dir && cd ~/dir
or
$ mkdir -p create/new/dir && cd create/new/dir
You can’t have a simple BASH script that reads “mkdir $1 && cd $1″ because it would only switch to the directory while running as a child process instead of actually switching to the directory.
However there is a quick and easy way to combine the tasks, add a function mkcd() to your .bashrc.
$ cat >> ~/bashrc
function mkcd(){
[ -n "$1" ] && mkdir -p “$@” && cd “$1″;
}