Posts Tagged ‘location’

Linux then and Now statistics diagram on GNU/Linux use grow 1994 – 2011

Tuesday, January 31st, 2012

Linux then and now developers line of code top 500 super computers and GNU / Linux 1994 - 2011, Kernel source code lines

 

In above graphics you see development of GNU/Linux through the years startingfrom 1992 to 2010.  You see for the past 18 years the number of kernel developers has rasised from 100 to 1000 (10 times). The number of super computers based on GNU / Linux operating system was only 1, while in 2011 they were already 413. Just for information Top 10 Super computers in terms of CPU power are running on top of some Linux + GNU environment based operating system.

Cell Phones baed on Linux or GNU sold worldwide, Internet users growth, PCs with linux shipped worldwide

You see the number of Patented software increased approximate 3 times for 16 years … PC shipped with Linux all oer the world increased almost 10 times.

GNU / Linux  user habits then and now pie, Where Linux is used most survey results

A survey was run among the biggest Linux convention LinuxCon aiming to find out the share difference between users using different distros, as well as a survey to answer the question where is Linux mostly used. Obviously even though the Ubuntu desktop boom this years Linux is still mostly used in work location, home desktop / notebook users are almost 3 times less.
The survey show the sad results,  the Linux in school and academic communities is less used than for professional purposes. On the desktop things has slightly changed, for the last 5-7 years. From the position of being a Linux Desktop leading OS, Fedora went into the shadows in favour of  the "less free" (in terms of Freedom) Ubuntu.

Linux users then and now, biggest successes and challenges for Linux and free software use and adoption

All system administrators knows well Linux is a very common choice for building small or middle enterprise business information systems. Hugest platforms which are the web backbone today like Google, Facebook, Twitter, Stock Exchanges,  Mail services, various technical equipment etc. runs on top of Linux. Even though the huge number of adoption Linux and free software is though to not be legally assured this is well known among free software and open source evangelist under the term FUD.

Android found its way also in Samsung Galaxy and a number of tablet devices running Linux based kernel OS was shipped in 2011.

With the raise of Android which (base is mostly Linux kernel and less GNU tools based). The spread of Linux has seen a huge raise on the mobile (smart phones) market as well. You see in above chart as of 2011 Android sells had the highest market share  with 37%.
The year 2011 was not among the best Linux users anywas, as Unity does turned away many users to become Linux converts. The big GNOME 3 mess, which was called by Linus Toravlds a "holy mess" , along with the kernel.org's security break in does also contributed that year 2011 ended up as a bad one for free software.

Linux, Windows 7, Vista, XP, MacOS X, iOS market share chart

As of August 2011, the global Linux market approximate market share is about 3% of all the installed OSes currently existing in the world. And compared to 5 years ago there is a little decline in the share. I believe the 2012 will be a better year for both development and adoption of free software and Linux.

 

Where does Debian GNU / Linux Apache + PHP stores session files?

Tuesday, November 22nd, 2011

In order to debug some PHP session problems on Debian, I needed to check the count of existing session files.
When PHP is compiled from source usually, by default sessions are stored in /tmp directory, however this is not the case on Debian.

Debian’s PHP session directory is different, there the sessions are stored in the directory:

/var/lib/php5

I’ve discovered the session directory location by reading Debian’s cron shell script, which delete session files on every 30 minutes.

Here is the file content:

debian~# cat /etc/cron.d/php5
# /etc/cron.d/php5: crontab fragment for php5
# This purges session files older than X, where X is defined in seconds
# as the largest value of session.gc_maxlifetime from all your php.ini
# files, or 24 minutes if not defined. See /usr/lib/php5/maxlifetime

# Look for and purge old sessions every 30 minutes
09,39 * * * * root [ -x /usr/lib/php5/maxlifetime ] &&
[ -d /var/lib/php5 ] && find /var/lib/php5/ -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete

To check the amount of existing PHP opened session files:

debian:~# ls -1 /var/lib/php5|wc -l
14049

How to copy CD or DVD on GNU/Linux and FreeBSD using console or terminal

Monday, November 14th, 2011

CD Burning Console Terminal Linux / FreeBSD picture

These days more and more people start to forget the g* / Linux old times when we used to copy CDs from console using dd in conjunction with mkisofs .

Therefore to bring some good memories back of the glorious console times I decided to come up with this little post.

To copy a CD or DVD the first thing one should do is to make an image copy of the present inserted CD into the CD-drive with dd :

1. Make copy of the CD/DVD image using dd

# dd if=/dev/cdrom of=/tmp/mycd.iso bs=2048 conv=notrunc

/dev/cdrom is the location of the cdrom device, on many Linuces including (Debian) /dev/cdrom is just a link to the /dev/ which corresponds to the CD drive. Note on FreeBSD the location for the CD Drive is /dev/acd0
/tmp/mycd.iso instructs dd CD image creation to be placed in /tmp/ directory.
bs argument instructs it about the byte size portions by which the content of the CD-Drive inserted CD will be read. bs value of 2048 is actually only 2KB per dd read, increasing this value will decrease the time required for the CD image to be extracted.

2. Prepare CD image file to be ready for burning

After dd completes the image copy operation, next to prepare the extracted image / ISO to be ready for burning mkisofs is used:

# mkisofs -J -L -r -V TITLE -o /tmp/imagefile.iso /tmp/mycd.iso

The -J option makes the CD compatible for Pcs running Microsoft Windows. The -V TITLE option should be changed to whatever title the new CD should have, -r will add up status bar for the mkisofs operation.
-r is passed to create specific file permissions on the newly created CD, -o specifies the location where mkisofs will produce its file based on the CD image /tmp/mycd.iso .

3. Burning the mkisofs image file to a CD/DVD on GNU / Linux

linux:~# cdrecord -scanbus
linux:~# cdrecord dev=1,0,0 /tmp/imagefile.iso

If all wents okay with cdrecord operation, after a while the CD should be ready.

4. Burning the mkisofs image file to CD on FreeBSD

freebsd# burncd -f /dev/acd0 data /tmp/imagefile.iso fixate

How rescue unbootable Windows PC, Windows files through files Network copy to remote server shared Folder using Hirens Boot CD

Saturday, November 12th, 2011

hirens-boot-cd-logo-how-to-rescue-unbootable-pc-with-hirens-bootcd
I'm rescuing some files from one unbootable Windows XP using a livecd with Hirens Boot CD 13

In order to rescue the three NTFS Windows partitions files, I mounted them after booting a Mini Linux from Hirens Boot CD.

Mounting NTFS using Hirens BootCD went quite smoothly to mount the 3 partitions I used cmds:

# mount /dev/sda1 /mnt/sda1
# mount /dev/sda2 /mnt/sda2
# mount /dev/sdb1 /mnt/sdb1

After the three NTFS file partitions are mounted I used smbclient to list all the available Network Shares on the remote Network Samba Shares Server which by the way possessed the NETBIOS name of SERVER 😉

# smbclient -L //SERVER/
Enter root's password:
Domain=[SERVER] OS=[Windows 7 Ultimate 7600] Server=[Windows 7 Ultimate 6.1]

Sharename Type Comment
——— —- ——-
!!!MUSIC Disk
ADMIN$ Disk Remote Admin
C$ Disk Default share
Canon Inkjet S9000 (Copy 2) Printer Canon Inkjet S9000 (Copy 2)
D$ Disk Default share
Domain=[SERVER] OS=[Windows 7 Ultimate 7600] Server=[Windows 7 Ultimate 6.1]
Server Comment
——— ——-
Workgroup Master
——— ——-

Further on to mount the //SERVER/D network samba drive – (the location where I wanted to transfer the files from the above 3 mounted partitions):

# mkdir /mnt/D
# mount //192.168.0.100/D /mnt/D
#

Where the IP 192.168.0.100 is actually the local network IP address of the //SERVER win smb machine.

Afterwards I used mc to copy all the files I needed to rescue from all the 3 above mentioned win partitions to the mounted //SERVER/D
 

How to make wicd systray to appear in GNOME on Ubuntu 11.10 / How to fix missing wicd network manager systray on Ubuntu

Monday, November 7th, 2011

After upgrading my sis’s notebook from Ubuntu 11.04 to Ubuntu 11.10 on her Acer Aspire 5736Z the default gnome wireless network manager started behaving oddly.
The Network Manager did not show any networks, even though the network drivers showed that are loaded properly on the Linux host and using the normal commands like iwlist or iwconfig I could list and see the networks and even connect to a network.

As my sister is not a console geek like me it was necessery of course to have an easy way to connect herself to the Internet with nice GUI application. I personally love WICD Network Manager and as the default gnome manager was misbehaving I immediately installed her wicd.
With wicd , the wireless networks were properly listed and there was no connection issues to the wireless networks, however the wicd system tray was missing and hence everytime she wanted to connect to a wireless network, she had to keep wicd-client running active in the Dock or run it manually every time on connect, when she had to change her physical location and connect to another wireless network.
This of course is quite unhandy and gives her a bad image of Linux and I definitely want to make her love free software and GNU / Linux. Thus I want to give her a GNU / Linux she will be easy to use.

To make her more satisfied with her Ubuntu I googled around to see what causes the wicd systray to be missing after some research online I found out, its probably due to either wicd bug or some kind of interface changes in unity newer versions of Ubuntu. Some people online suggested a fix via changing values in gconf-editor but this work around by changing the values in gconf-editor:

'desktop' -> 'unity' -> 'panel'

I tried this suggested fix which was reported to work on Ubuntu 11.04 but the gconf registry suggested pathway was missing at all so this solution did not worked.

I further read some other suggested solution using wicd-client by invoking it with two args like so:

stanimira@ubuntu:~$ wicd-client -n &
...stanimira@ubuntu:~$ wicd-client -a &

This proposed solution did not worked either, then I found in one of the Ubuntu bugs reports, a little shell script (add-wicd-to-whitelist.sh) that changes some values in gconf so I proceeded downloaded and give it a try:

stanimira@ubuntu:~$ wget http://www.pc-freak.net/files/add-wicd-to-whitelist.sh
...
stanimira@ubuntu:~$ sh add-wicd-to-whitelist.sh
...

For my surprise running the script doesn’t immediately changed nothing and wicd wireless connectivity indicator was still missing from the tray.
I thought it might need to reload gnome so I give it a restart and HOORAY! after the restart the WICD connected wireless strength show up, like you can see in the screenshot below 😉

Wicd indicator running in systray on GNOME in Ubuntu 11.10

Now hope this fix will, help out there experiencing the same issues to work around his wireless network connectivity issues 😉 Cheers.

How to set a crontab to execute commands on a seconds time interval on GNU / Linux and FreeBSD

Sunday, October 30th, 2011

crontab-execute-cron-jobs-every-second-on-linux-cron-logo
Have you ever been in need to execute some commands scheduled via a crontab, every let’s say 5 seconds?, naturally this is not possible with crontab, however adding a small shell script to loop and execute a command or commands every 5 seconds and setting it up to execute once in a minute through crontab makes this possible.
Here is an example shell script that does execute commands every 5 seconds:

#!/bin/bash
command1_to_exec='/bin/ls';
command2_to_exec='/bin/pwd';
for i in $(echo 1 2 3 4 5 6 7 8 9 10 11); do
sleep 5;
$command1_to_exec; $command2_to_exec;
done

This script will issue a sleep every 5 seconds and execute the two commands defined as $command1_to_exec and $command2_to_exec

Copy paste the script to a file or fetch exec_every_5_secs_cmds.sh from here

The script can easily be modified to execute on any seconds interval delay, the record to put on cron to use with this script should look something like:

# echo '* * * * * /path/to/exec_every_5_secs_cmds.sh' | crontab -

Where of course /path/to/exec_every_5_secs_cmds.sh needs to be modified to a proper script name and path location.

Another way to do the on a number of seconds program / command schedule without using cron at all is setting up an endless loop to run/refresh via /etc/inittab with a number of predefined commands inside. An example endless loop script to run via inittab would look something like:

while [ 1 ]; do
/bin/ls
sleep 5;
done

To run the above sample never ending script using inittab, one needs to add to the end of inittab, some line like:

mine:234:respawn:/path/to/script_name.sh

A quick way to add the line from consone would be with echo:

echo 'mine:234:respawn:/path/to/script' >> /etc/inittab

Of course the proper paths, should be put in:

Then to load up the newly added inittab line, inittab needs to be reloaded with cmd:

# init q

I've also red, some other methods suggested to run programs on a periodic seconds basis using just cron, what I found in stackoverflow.com's  as a thread proposed as a solution is:

* * * * * /foo/bar/your_script
* * * * * sleep 15; /foo/bar/your_script
* * * * * sleep 30; /foo/bar/your_script
* * * * * sleep 45; /foo/bar/your_script

One guy, even suggested a shorted way with cron:

0/15 * * * * * /path/to/my/script

Fix of “Unable to allocate memory for pool.” PHP error messages

Saturday, October 15th, 2011

Since some time, I don’t know exactly where, after some updates of my WordPress running on a small server with FreeBSD 7.2. I’ve started getting a lot of Apache crashes. Often the wordpress scripts stopped working completely and I got only empty pages when trying to process the wordpress blog in a browser.

After a bunch of reading online, I’ve figured out that the cause might be PHP APC stands for Alternative PHP Cache .

I was not sure if the PHP running on the server had an APC configured at all so I used a phpinfo(); script to figure out if I had it loaded. I saw the APC among the loaded to show off in the list of loaded php modules, so this further led me to the idea the APC could be really causing the unexpected troubles.

Thus first I decided to disable the APC on a Virtualhost level for the domain where the crashing wordpress was hosted, to do I placed in the VirtualHost section in the Apache configuration /usr/local/etc/apache2/httpd.conf the following config directive:

php_flag apc.cache_by_default Off

These get me rid of the multiple errors:

PHP Warning: require_once() [function.require-once]: Unable to allocate memory for pool. in /usr/local/www/data-dist/blog/wp-content/plugins/tweet-old-post/top-admin.php on line 6

which constantly were re-occuring in php_error.log:

Further after evaluating all the websites hosted on the server and making sure none of which was really depending on APC , I’ve disabled the APC completely for PHP. To do so I issued:

echo 'apc.enabled = 0' >> /usr/local/etc/php.ini

Similarly on GNU/Linux to disable globally APC from PHP only the correct location to php.ini should be provided on Debian this is /etc/php5/apache2/php.ini .

How to play VCD videos in Debian Linux

Monday, September 26th, 2011

Totem VCD error occured, could not open location you might not have permissions to open the file

A friend of mine gave me a VCD with some coptic Orthodox Christian exorcism, where there pope was chasing some evil spirits from possessed muslims who came to the Coptic Orthodox Church in egypt. The video was made to be in VCD and as you can expect this did not worked out of the box with Totem and VLC out of the box.
Putting in the VCD video inside my cdrom poped up an error like the one in the header of the post.
In order to make the video play I had to use the old school and now a bit obsolete mplayer.
Hence in order to play the VCD on Debian Linux I had to install mplayer and w32codecs packages first e.g.:

debian:~# apt-get update && apt-get install mplayer w32codecs

Second to play the video from gnome-terminal, I had to switch to the mounted cdrom location /media/cdrom0 and launch the video with mplayer cmd like so:

debian:~$ cd /media/cdrom0/vcd
debian:/media/cdrom0/vcd$ mplayer vcd://2
...

In some cases it might be necessery to play the video with mplayer command like:

debian:/media/cdrom0/vdd$ mplayer vcd://2 vcd://3

Watching it with mplayer from console has some downsides as I couldn’t make the fast rewind work, but still it’s way better than nothing.
Too bad in Debian Squeeze 6 gmplayer is no longer installable. The gmplayer can probably be installed if mplayer is compiled from source, but I’m too lazy to try it out.
I’ve red also in some forums online that gxine is capable of playing the VCD play nice, but I couldn’t install it from my existing Debian repositories so I did not give it a go.

Two wordpress plugins to accelerate wordpress opening times and decrease server load time

Thursday, September 22nd, 2011

A Comparison of wordpress webpage responce with and without wp dbcache

A combination of two wordpress caching plugins (Hyper Cache and Db Cachesignificantly improves the access times of a wordpress based blogs and websites.

Installing the two websites has drastically improved my blog opening times, so in my view having the two plugins on every wordpress install out there is a must! 🙂
The plugins installation is straight forward, here is how I installed them.

1. Installing Hyper Cache on WordPress

To install Hyper Cache all I had to do is download and enable the plugin, the plugin doesn’t require any configuration. I always love it when I don’t have to bother with reading configuration options and pondering for some 20 minutes on the plugin features, so in that perspective Hyper Cache in my view is a good alternative to WordPress Super Cache

Besides that WordPress Super Cache was having issues when enabled on few wordpress based websites I manage these days. For comparison Hyper Cache worked just great on all wordpress install I tried the plugin so far.

To install all I had to do is download the plugin unzip and enable it:

a. Download and unzip it

debian:/var/www/blog# wget http://downloads.wordpress.org/plugin/hyper-cache.zip
...
debian:/var/www/blog# cd wp-content/plugins
debian:/var/www/blog/wp-content/plugins# unzip hyper-cache.zip

b. Enable Hyper Cache plugin

To enable the plugin follow to standard plugin location;

Plugins -> Inactive -> Hyper Cache (Enable)

To enable the plugin follow to standard plugin location;

Plugins -> Inactive -> Hyper Cache (Enable)

 

A  mirror of current version of hyper-cache.zip plugin is here 

2. Installing Wodpress Db Cache

What Db Cache, does it does caching of last queries made to MySQL for specified time, so if the query has to be refetched again from wordpress’s php frontend the queries results are fetched straight for the memory. This decreases the load towards the MySQL server and increases the webpages loading time.

As the plugin page suggests it’s way faster than other html caching-plugins like WP-Cache  or WP Super Cache

However, I think its still slower than using a combination of WP Super Cache’s alternative Hyper Cache  and  Db Cache . Combining this two could rise the webpage opening times according to some statisticonline at best cases up to 830% !! 😉 Let me proceed with how I did the install of  Db Cache .

a. Download and Install Db Cache

 

debian:/var/www/blog/wp-content/plugins# wget http://downloads.wordpress.org/plugin/db-cache.0.6.zip

...

debian:/var/www/blog/wp-content/plugins# unzip db-cache.0.6.zip

 

b. Enable the plugin 

 

Plugins -> Inactive -> Db Cache (Enable)

 

c. Make sure the permissions for Db Cache are correct

On Debian to enable Db Cache, the permissions should be changed for Apache to have a read/write permissions to plugin directory, on Debian to fix the permissions I used the commands:

debian:/var/www/blog# chown www-data:www-data wp-content

debian:/var/www/blog# chown -R www-data:www-data wp-content/plugins/db-cache

On other GNU/Linux distributions the above commands (user and group) www-data:www-data, should be set to whatever user/group Apache is running with, on Slackware this would be nobody:nobody, on CentOS and RHEL it would be apache:apache.

Finally to enable Db Cache go to

Settings -> Db Cache -> (Tick Enable) -> Save

I’ve also made a mirror of Db Cache plugin here

Enjoy the speed boost 😉