Posts Tagged ‘bash shell script’

How to convert OGG Vorbis .ogg to MP3 on GNU / Linux and FreeBSD

Friday, July 27th, 2012

I’ve used K3B just recently to RIP an Audio CD with music to MP3. K3b has done a great job ripping the tracks, the only problem was By default k3b RIPs songs in OGG Vorbis (.ogg) and not mp3. I personally prefer OGG Vorbis as it is a free freedom respecting audio format, however the problem was the .ogg-s cannot be read on many of the audio players and it could be a problem reading the RIPped oggs on Windows. I’ve done the RIP not for myself but for a Belarusian gfriend of mine and she is completely computer illiterate and if I pass her the songs in .OGG, there is no chance she succed in listening the oggs. I’ve seen later k3b has an option to choose to convert directly to MP3 Using linux mp3 lame library this however is time consuming and I have to wait another 10 minutes or so for the songs to be ripped to shorten the time I decided to directly convert the existing .ogg files to .mp3 on my (Debian Linux). There are probably many ways to convert .ogg to mp3 on linux and likely many GUI frontends (like SoundConverter) to use in graphic env.

SoundConverter Debian GNU Linux graphic GUI environment program for convertion of ogg to mp3 and mp3 to ogg, convert multiple sound formats on GNU / Linux.

I however am a console freak so I preferred doing it from terminal. I’ve done quick research on the net and figured out the good old ffmpeg is capable of converting .oggs to .mp3s. To convert all mp3s just ripped in the separate directory I had to run ffmpeg in a tiny bash loop.

A short bash shell script 1 liner combined with ffmpeg does it, e.g.;

for f in *.ogg; do ffmpeg -i "$f" "`basename "$f" .ogg`.mp3"; done.....

The loop example is in bash so in order to make the code work on FreeBSD it is necessery it is run in a bash shell and not in BSDs so common csh or tcsh.

Well, that’s all oggs are in mp3; Hip-hip Hooray 😉

Auto restart Apache on High server load (bash shell script) – Fixing Apache server temporal overload issues

Saturday, March 24th, 2012

auto-restart-apache-on-high-load-bash-shell-script-fixing-apache-temporal-overload-issues

I've written a tiny script to check and restart, Apache if the server encounters, extremely high load avarage like for instance more than (>25). Below is an example of a server reaching a very high load avarage:;

server~:# uptime
13:46:59 up 2 days, 18:54, 1 user, load average: 58.09, 59.08, 60.05
load average: 0.09, 0.08, 0.08

Sometimes high load avarage is not a problem, as the server might have a very powerful hardware. A high load numbers is not always an indicator for a serious problems. Some 16 CPU dual core (2.18 Ghz) machine with 16GB of ram could probably work normally with a high load avarage like in the example. Anyhow as most servers are not so powerful having such a high load avarage, makes the machine hardly do its job routine.

In my specific, case one of our Debian Linux servers is periodically reaching to a very high load level numbers. When this happens the Apache webserver is often incapable to serve its incoming requests and starts lagging for clients. The only work-around is to stop the Apache server for a couple of seconds (10 or 20 seconds) and then start it again once the load avarage has dropped to less than "3".

If this temporary fix is not applied on time, the server load gets increased exponentially until all the server services (ssh, ftp … whatever) stop responding normally to requests and the server completely hangs …

Often this server overloads, are occuring at night time so I'm not logged in on the server and one such unexpected overload makes the server unreachable for hours.
To get around the sudden high periodic load avarage server increase, I've written a tiny bash script to monitor, the server load avarage and initiate an Apache server stop and start with a few seconds delay in between.

#!/bin/sh
# script to check server for extremely high load and restart Apache if the condition is matched
check=`cat /proc/loadavg | sed 's/\./ /' | awk '{print $1}'`
# define max load avarage when script is triggered
max_load='25'
# log file
high_load_log='/var/log/apache_high_load_restart.log';
# location of inidex.php to overwrite with temporary message
index_php_loc='/home/site/www/index.php';
# location to Apache init script
apache_init='/etc/init.d/apache2';
#
site_maintenance_msg="Site Maintenance in progress - We will be back online in a minute";
if [ $check -gt "$max_load" ]; then>
#25 is load average on 5 minutes
cp -rpf $index_php_loc $index_php_loc.bak_ap
echo "$site_maintenance_msg" > $index_php_loc
sleep 15;
if [ $check -gt "$max_load" ]; then
$apache_init stop
sleep 5;
$apache_init restart
echo "$(date) : Apache Restart due to excessive load | $check |" >> $high_load_log;
cp -rpf $index_php_loc.bak_ap $index_php_loc
fi
fi

The idea of the script is partially based on a forum thread – Auto Restart Apache on High Loadhttp://www.webhostingtalk.com/showthread.php?t=971304Here is a link to my restart_apache_on_high_load.sh script

The script is written in a way that it makes two "if" condition check ups, to assure 100% there is a constant high load avarage and not just a temporal 5 seconds load avarage jump. Once the first if is matched, the script first tries to reduce the server load by overwritting a the index.php, index.html script of the website with a one stating the server is ongoing a maintenance operations.
Temporary stopping the index page, often reduces the load in 10 seconds of time, so the second if case is not necessery at all. Sometimes, however this first "if" condition cannot decrease enough the load and the server load continues to stay too high, then the script second if comes to play and makes apache to be completely stopped via Apache init script do 2 secs delay and launch the apache server again.

The script also logs about, the load avarage encountered, while the server was overloaded and Apache webserver was restarted, so later I can check what time the server overload occured.
To make the script periodically run, I've scheduled the script to launch every 5 minutes as a cron job with the following cron:

# restart Apache if load is higher than 25
*/5 * * * * /usr/sbin/restart_apache_on_high_load.sh >/dev/null 2>&1

I have also another system which is running FreeBSD 7_2, which is having the same overload server problems as with the Linux host.
Copying the auto restart apache on high load script on FreeBSD didn't work out of the box. So I rewrote a little chunk of the script to make it running on the FreeBSD host. Hence, if you would like to auto restart Apache or any other service on FreeBSD server get /usr/sbin/restart_apache_on_high_load_freebsd.sh my script and set it on cron on your BSD.

This script is just a temporary work around, however as its obvious that the frequency of the high overload will be rising with time and we will need to buy new server hardware to solve permanently the issues, anyways, until this happens the script does a great job 🙂

I'm aware there is also alternative way to auto restart Apache webserver on high server loads through using monit utility for monitoring services on a Unix system. However as I didn't wanted to bother to run extra services in the background I decided to rather use the up presented script.

Interesting info to know is Apache module mod_overload exists – which can be used for checking load average. Using this module once load avarage is over a certain number apache can stop in its preforked processes current serving request, I've never tested it myself so I don't know how usable it is. As of time of writting it is in early stage version 0.2.2
If someone, have tried it and is happy with it on a busy hosting servers, please share with me if it is stable enough?

How to fix upside-down / inverted web camera laptop Asus K51AC issue on Ubuntu Linux and Debian GNU / Linux

Monday, February 13th, 2012

Skype Video Inverted bat like linux screenshot

Does your camera show video correctly in cheese but shows captured video upside-down (inverted) in skype ?
This is an issue a friend of mine experienced on his Asus K51AC-SX037D laptop on both Ubuntu and Debian Linux.
As you can see in the picture above it is funny as with this bug the person looks like a batman 😉
As the webcam upside-down issue was present on both latest Ubuntu 11.10 and latest stable Debian Squeeze 6.02, my guess was other GNU / Linux rpm based distro like Fedora might have applied a fix to this weird Skype inverted video (bat human like) issue.
Unfortunately testing the webcam with Skype on latest both Fedora 16 and Linux Mint 12 appeared to produce the same webcam bug.

A bit of research for the issue online and try outs of a number of suggested methods to resolve the issue led finally to a work around, thanks to this post
Here is few steps to follow to make the webcam show video like it should:

1. Install libv4l-0 package

root@linux:~# apt-get --yes install libv4-0
...

Onwards to start skype directly from terminal and test the camera type:

hipo@linux:~$ LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so skype

This is the work around for 32 bit Linux install, most people however will probably have installed 64 bit Linux, for 64bit Linux installs the above command should be little different:

hipo@linux:~$ LD_PRELOAD=/usr/lib32/libv4l/v4l1compat.so skype

Once skype is launched test the camera and see if the camera capture is now uninverted, through menus:

S -> Options -> Video Devices -> Test

Skype Options Video devices screenshot

2. Create a skype Wrapper script Launcher

To make skype launch everytime with exported shell variable:
LD_PRELOAD=/usr/lib32/libv4l/v4l1compat.so

A new skype wrapper bash shell script should be created in /usr/local/bin/skype , the file should contain:

#!/bin/sh
LD_PRELOAD=/usr/lib32/libv4l/v4l1compat.so
/usr/bin/skype

To create the script with echo in a root terminal issue;

root@linux:~# echo '#!/bin/sh' >> /usr/local/bin/skype
root@linux:~# echo 'LD_PRELOAD=/usr/lib32/libv4l/v4l1compat.so' >> /usr/local/bin/skype
root@linux:~# echo '/usr/bin/skype' >> /usr/local/bin/skype
root@linux:~# chmod +x /usr/local/bin/skype

3. Edit the Skype gnome menu to substitute /usr/bin/skype Skype Launcher with /usr/local/bin/skype

Gnome 2 has a handy menu launcher, allowing to edit and add new menus and submenus (menus and items) to the Application menu, to launch the editor one has to click over Applications with last mouse button (right button) and choose Edit Menus

GNOME Edit menus screenshot

The menu editor like the one in the below screenshot will appear:

GNOME 2 Menu Editor Screenshot

In the preceeding Launcher properties window, Command: skype has to be substituted with:

GNOME2 Skype screenshot Launcher properties

Command: /usr/local/bin/skype

For console freaks who doesn't want to bother in editting Skype Launcher via GUI /usr/share/applications/skype.desktop file can be editted in terminal. Inside skype.desktop substitute:

Exec=skype

with

Exec=/usr/local/bin/skype

Skype fixed inverted bat like screenshot

As one can imagine the upside-down video image in Skype is not a problem because of Linux, but rather another bug in Skype (non-free) software program.
By the way everyone, who is using his computer with Free Software operating system FreeBSD, Linux etc. knows pretty well by experience, that Skype is a very problematic software; It is often a cause for system unexpected increased system loads, problems with (microphone not capturing), camera issues, issues with pulseaudio, problem with audio playbacks … Besides the long list of bugs there are unexpected display bugs in skype tray icon, bugs in skype messanger windows and at some rare occasions the program completely hangs and had to be killed with kill command and re-launched again.

Another worrying fact is Skype's versions available for GNU / Linux and BSD is completely out of date with its "competitor" operating systems MS Windows, MacOS X etc.
For people like me and my friend who want to use free operating system the latest available skype version is not even stable … current version fod download from skype's website is (Skype 2.2Beta)!

On FreeBSD the skype situation is even worser, freebsd have only option to run Skype ver 1.3 or v. 2.0 at best, as far as I know skype 2.2 and 2.2beta is not there.

Just as matter of comparison the latest Skype version on Windows is 5.x. Windows release is ages ahead its Linux and BSD ver. From a functional point of view the difference between Linux's 2.x and Windows 5.x is not that much different, what makes difference is is the amount of bugs which Linux and BSD skype versions contain…
Skype was about 6 months ago bought by Microsoft, therefore the prognosis for Skype Linux support in future is probably even darker. Microsoft will not probably bother to release new version of Skype for their competitor free as in freedom OSes.

I would like to thank my friend and brother in Christ Stelian for supplying me with the Skype screenshots, as well as for being kind to share how he fixed his camera with me.

How to take multiple screenshots with scrot and ImageMagick import commands in terminal on GNU / Linux and FreeBSD

Friday, January 13th, 2012

scrot and import are two commands, which can be used to take screenshot in terminal on Linux and FreeBSD:

To use scrot cmd to take screenshots on Ubuntu and Debian the scrot package has to be installed:

noah:~# apt-get install scrot
...

scrot should also be available on most other Linux distributions in the main repositories, I'll be glad to hear if someone has used it on Fedora, SUSE etc.

On FreeBSD, there is a port called scrot , to install on FreeBSD:

freebsd# cd /usr/ports/graphics/scrot
freebsd# make install clean
...

Scrot has plenty of nice arguments one can use to make a screenshot. Maybe the most handy one in my view is after a preliminary set delay before screenshot is taken.

To take screenshot with it after lets say 5 seconds delay before the screenshot:

hipo@noah:~/Desktop$ scrot -t 20 -d 5

Screenshot scrot my debian Linux gnome-termina

To put an year, month and day and year followed by screen resolution with scrot :

hipo@noah:~$ scrot '%Y-%m-%d_$wx$h.png'

Another way to take a screenshot of screen with command is by using ImageMagick'simport image manipulation package.
To take screenshot of the current screen via terminal using import , type in xterm, gnome-termina or Gnome's Run Application (ALT+F2)

hipo@noah:~$ import -window root ScreenShot.png

To make import command to save the taken screenshot in a format (minute:hour:day:month:year)i :

hipo@noah:~$ import -window root $screenshot_dir/screenshot-$(date +%M_%k_%d_%m_%Y|sed -e 's/^ *//').png

Taking a delayed screenshot is also possible via The GIMP via menus File -> Create -> Screenshot

GIMP Screenshot 15 seconds delay GIMP window screenshot

Now here is an interesting question, what if I would like to take periodic screenshots of what I do on my Desktop to take random movie scenes from a movie I watch with totem or vlc??

This task is quite easily achiavable with a little bash shell script, I wrote:

screenshot_dir='Screenshots';
seconds='60';
if [ ! -d "$screenshot_dir" ]; then
mkdir $screenshot_dir;
fi
while [ 1 ]; do
sleep $seconds;
(import -window root $screenshot_dir/screenshot-$(date +%M_%k_%d_%m_%Y|sed -e 's/^ *//').png) &
done

This script will take screenshot automatically to Screenshots/ directory every (1 min – 60 seconds)
You can also my downloads take_screenshot_every_60_secs_import.sh here

To use take_screenshot_every_60_secs_import.sh just issue the script inside xterm or gnome-terminal, after that simply use your computer as you normally would.
The script will take snapshots every minute and store all taken screenshots in Screenshots dir.

If you prefer to use scrot to take automatically the screenshots every lets say 5 minutes, you can use a script like:

screenshot_dir='Screenshots';
# 300 secs (5 mins)seconds='300';
if [ ! -d "$screenshot_dir" ]; then
mkdir $screenshot_dir;
fi
while [ 1 ]; do
sleep $seconds;
(scrot $screenshot_dir/'%Y-%m-%d_$wx$h.png') &
done

You can fetch take_screenshot_every_60_secs_scrot.sh here

The script using scrot is better in terms of efficiency, the system load scrot will put on your machine will be less.
Using some of this scripts will be handy if you need screenshots to Movies, Programs and favourite Free Software games.
Hope this is educative to someone 😉

How to add cron jobs from command line or bash scripts / Add crontab jobs in a script

Saturday, July 9th, 2011

I’m currently writting a script which is supposed to be adding new crontab jobs and do a bunch of other mambo jambo.

By so far I’ve been aware of only one way to add a cronjob non-interactively like so:

                 linux:~# echo '*/5 * * * * /root/myscript.sh' | crontab -

Though using the | crontab – would work it has one major pitfall, I did completely forgot | crontab – OVERWRITES CURRENT CRONTAB! with the crontab passed by with the echo command.
One must be extremely careful if he decides to use the above example as you might loose your crontab definitions permanently!

Thanksfully it seems there is another way to add crontabs non interactively via a script, as I couldn’t find any good blog which explained something different from the classical example with pipe to crontab –, I dropped by in the good old irc.freenode.net to consult the bash gurus there 😉

So I entered irc and asked the question how can I add a crontab via bash shell script without overwritting my old existing crontab definitions less than a minute later one guy with a nickname geirha was kind enough to explain me how to get around the annoying overwridding.

The solution to the ovewrite was expected, first you use crontab to dump current crontab lines to a file and then you append the new cron job as a new record in the file and finally you ask the crontab program to read and insert the crontab definitions from the newly created files.
So here is the exact code one could run inside a script to include new crontab jobs, next to the already present ones:

linux:~# crontab -l > file; echo '*/5 * * * * /root/myscript.sh >/dev/null 2>&1' >> file; crontab file

The above definition as you could read would make the new record of */5 * * * * /root/myscript.sh >/dev/null be added next to the existing crontab scheduled jobs.

Now I’ll continue with my scripting, in the mean time I hope this will be of use to someone out there 😉

Runing sudo command simultaneously on multiple servers with SSHSUDO

Tuesday, June 21st, 2011

ssh multiple server command execute
I just was recommended by a friend a nifty tool, which is absoutely nifty for system administrators.

The tool is called sshsudo and the project is hosted on http://code.google.com/p/sshsudo/.

Let’s say you’re responsible for 10 servers with the same operating system let’s say; CentOS 4 and you want to install tcpdump and vnstat on all of them without logging one by one to each of the nodes.

This task is really simple with using sshsudo.
A typical use of sshsudo is:


[root@centos root]# sshsudo -u root \
comp1,comp2,comp3,comp4,comp5,comp6,comp7,comp8,comp9,comp10 yum install tcpdump vnstat

Consequently a password prompt will appear on the screen;
Please enter your password:

If all the servers are configured to have the same administrator root password then just typing one the root password will be enough and the command will get issued on all the servers.

The program can also be used to run a custom admin script by automatically populating the script (upload the script), to all the servers and issuing it next on.

One typical use to run a custom bash shell script on ten servers would be:


[root@centos root]# sshsudo -r -u root \
comp1,comp2,comp3,comp4,comp5,comp6,comp7,comp8,comp9,comp10 /pathtoscript/script.sh

I’m glad I found this handy tool 😉

How to add multiple email accounts in qmail’s vpopmail with vpasswd via ssh (console) / Little shell script to add multiple email addresses

Sunday, June 12th, 2011

I’ve been assigned the task to add on one of the qmail powered servers I administrate about 50 email addresses via command line.

Each email addresses was required to be configured to have the same mail password.
Adding the email addresses via an interface would be a killing time consuming task and will probably require at least 1 hour of time to add the emails with qmailwebmin, qadmin, qubit or the other vpopmail qmail web administration interfaces available nowdays.

To solve the task, I’ve used a line oner bash shell script which reads all my 80 emails from a file and adds them with vpopmail’s command line tool vpasswd on the mail server.

Here is the one liner shell script I’ve written to solve the task:

debian:~# while read line; do vadduser $line Email_Pass_Phrase; done < email_list_file.txt

In above’s code I’ve used the email_list_file.txt file is a text file on the server and contains list of all my 50 email addresses, where each line in the file contains one email. The Email_Pass_Phrase is actually the password I’ve set for all the new email addresses being created with vpasswd

That’s all now the 50 email addresses on the server are created and I’ve saved at least one hour of boring repeating actions in the browser 😉