http://www.linux.com/news/featured-blogs/200-libby-clark/640691-pros-and-cons-of-building-a-private-cloud-with-open-source-ganeti


Businesses considering building a private cloud with open source tools have likely explored at least one of the big three open IaaS options: OpenStack, CloudStack and Eucalyptus. These are great platforms for IT departments that have the time and technical expertise to test and deploy large clouds.
But what works for enterprise customers isn’t necessarily ideal for small to medium-size businesses or academic institutions with less demand for computing resources and a small IT staff, says Lance Albertson, associate director of operations at Oregon State University’s Open Source Lab.

That’s why the OSU Open Source Lab is running its private production and development cloud on Ganeti, an open source virtualization management platform developed at Google.
Google originally started Ganeti in 2005-2006 as a VMware alternative for managing virtual machines (VMs), storage and networks – not as a cloud platform. So it’s missing many of the features, such as elastic-style computing, cloud-based storage and object APIs that come with the bigger open cloud projects, said Iustin Pop, lead developer for Ganeti at Google, via email.
It can be used for single-host management, similar to Libvirt or Xen Tools, as well as large-scale computing on the OpenStack level, Pop said. But Ganeti’s sweet spot lies somewhere in the middle: “from one to two physical machines to a couple hundred, focused on private use of traditional VMs.”
“If you want to run hundreds of stable Linux-based VMs, Ganeti is a good option,” Pop said. “If you want to provide a public facing web-based interface for dynamic VM creation/turndown, there are better projects out there.”
At Google, Ganeti doesn’t touch any of the user-facing services such as email or Web search. It runs only internal corporate services such as DNS and cache servers used by the engineering workstations.

Pros of Ganeti

OSU’s Albertson is aware of the project’s limitations. But, he says, Ganeti has proven to be the perfect production and development environment to quickly and easily spin up virtual machines for the open source projects housed at OSU’s Open Source Lab, including Busybox, Inkscape, OpenMRS, phpBB, OSGeo, Python Software Foundation and Yum.


The lab’s Ganeti cloud is built for high availability and resiliency. Because it primarily uses local storage for virtual machines instead of a disk image mounted over NFS, the Ganeti cloud can generally perform faster than other cloud environments and at a lower hardware cost, Albertson said.
“If one of the physical nodes goes down we can easily bring the affected virtual machines back online on another node very quickly,” Albertson said. “Other cloud platforms don’t necessarily have hardware failure resiliency built into the platform as elegantly.”
They can also expand a Ganeti cluster with built-in utilities that can easily add a node with minimal downtime and even automatically re-balance the cluster.
“It really boils down to what you need. Other platforms have a lot of other useful features but it generally comes with a lot of angst, in building, testing and deploying more complex systems,” he said. “Ganeti is really simple to set up and maintain and fits well with how we provide virtual machine hosting.”

Cons of Ganeti

Ganeti’s simplicity can also be a challenge. For example, it doesn’t automatically shift resources when a node fails. Someone has to be there, manning the ship.
It’s command line driven so there’s no nice Web interface for users to interact with the system – a problem the Open Source Lab’s Ganeti Web Manager Project aims to fix.
“We’re making a lot of headway to improve the interface for more general users, “ Albertson said. “Right now it’s mostly useful for admins that want to give console access to their own virtual machines.
“We’ve also added quota support and a permission system,” he said, “So we’ve tried to extend Ganeti to be more cloud-like in that sense.”
Ganeti has its own API, but it isn’t compatible with Amazon’s API – or any other APIs.
“It’s really meant to be a private IaaS, keeping things in-house mostly,” Albertson said.
“I can see this being useful for small businesses that want to run a few virtual machines for their systems in a closet somewhere,” he said. “Trying to do that with OpenStack or the others? It’s just too much complexity for that size of scale.”

http://tuts.pinehead.tv/2012/09/25/tutorial-playing-around-with-mplayer


This tutorial handles about the usage of the wonderful media player MPlayer. It explains several options, lists some useful keyboard shortcuts and handles about tips and tricks that can be used to enhance your multimedia experience.
Difficulty: Basic

Note: this tutorial assumes that you have MPlayer installed & working and that you have some basic shell knowledge.

Playing a file

The most simple way of invoking MPlayer to play a media file is this:

[rechosen@localhost ~]$ mplayer

MPlayer will try to auto-detect what kind of file you’re trying to play (it usually succeeds) and play it. If it’s an audio file, it’ll just start playing and show its status and possible warnings on the command-line. If it’s a video file, it’ll open a window to play it in and then start playing.

Seeking through a file

You can seek through a file with a set of 3 keyboard shortcut pairs. Each pair makes MPlayer seek a different amount of time, and the pair consists of a key for seeking backward and a one for seeking forward. Listed below are those key pairs, for seeking backward and forward respectively:

• Left arrow and Right arrow (10 seconds)
• Down arrow and Up arrow (1 minute)
• Page down and Page up (10 minutes)

Knowing these will come in handy a lot of times.

Playing a DVD

MPlayer does not have DVD menu support (sadly), but it does support playing DVD’s. You can play a DVD this way:

mplayer dvd://

Replace with a number, like 1, 2 or 3. I personally prefer xine for DVD playback, as xine does support DVD menus.

Playing with subtitles

You can play a movie with subtitles in multiple ways. When playing a movie file, you can specify a subtitle file this way:

[rechosen@localhost ~]$ mplayer -sub

When playing a DVD movie, you can also use the DVD’s subtitle by specifying a language code like this:

[rechosen@localhost ~]$ mplayer dvd:// -slang nl,en

The above command would try to use dutch subtitles first, and fall back on english ones if dutch subtitles weren’t available.

Useful keyboard shortcuts

A list of useful keyboard shortcuts (sometimes called hotkeys) in MPlayer:
(note that the full list can be found in MPlayer’s man page)

• “f” => Toggle between full-screen and windowed mode during video playback (you can set the option -fs on the command line to make MPlayer start playing in full-screen mode immediately)
• “o” => Switch OSD (OnScreen Display) mode during video playback (for viewing how much time the movie has been playing and what its total lenght is)
• “p” or Space => Pause / resume playback
• “q” or Esc => Quit MPlayer (Esc does not quit but only stops playback when in GUI mode)
• “/” and “*” (or “9″ and “0″) => Decrease / increase playback volume respectively
• “m” => Mute sound (toggle)
• “T” (usually Shift + “t”) => Toggle stay-on-top (very useful if you don’t want your video window to be overlapped by an other application)
• “b” and “j” => Cycle through available subtitles
• “x” and “z” => Adjust subtitle delay (useful if you have a subtitle that isn’t 100% synced; you can then correct the time difference on the fly)
• “I” (usually Shift + “i”) => Show the filename of the movie being played (useful if you want to know that without interrupting the movie)
• “1″ and “2″ => Adjust contrast*
• “3″ and “4″ => Adjust brightness*
• “5″ and “6″ => Adjust hue*
• “7″ and “8″ => Adjust saturation*

*: These do not always work; see the MPlayer man page.

Generating an index

Sometimes, video files (mainly AVI files) have a corrupted index, or no index at all. This frequently is the case with incorrectly or incompletely downloaded files. Fortunately, MPlayer can generate the index it needs to play the file correctly. By using the -idx option, you can tell MPlayer to generate an index when necessary:

[rechosen@localhost ~]$ mplayer -idx

Sometimes the file does contain an index, but a corrupted one. In those cases, you might need to force MPlayer to generate an index:

[rechosen@localhost ~]$ mplayer -forceidx

Generating an index can take some time, depending on the size of the video file, but after that, the file should play correctly.

Correcting bad audio/video sync

Some videos (mainly flv files) are encoded in a horrible way, and MPlayer will have enormous trouble with the A/V (Audio/Video) sync. There are pretty much two possibilities in this case:

• MPlayer is trying to fix it but the sync is worsening too fast
• MPlayer is trying to fix something that’s already right and therefore pushes the sync away unnecessarily

In the first case, you should allow MPlayer to try harder to fix the sync:

[rechosen@localhost ~]$ mplayer -autosync 30 -mc 2.0

In the second case, you shouldn’t allow MPlayer to fix anything when it comes to the sync:

[rechosen@localhost ~]$ mplayer -autosync 0 -mc 0

You might wonder what those options mean. Well, setting autosync to a positive value allows MPlayer to gradually adapt its A/V correction algorithm. The higher the value, the faster MPlayer will try to correct it. The mc option specifies how many seconds MPlayer may correct every frame. Setting it to a high value (like 2.0) practically allows MPlayer to do whatever it thinks it should to correct the A/V sync. Setting it to 0 stops MPlayer from trying anything when it comes to syncing.

Using MPlayer on slow systems

As video playback is a CPU-intensive task, older and slower systems may have a hard time to play certain video files. MPlayer has a feature that will help them to keep up the playback with less CPU power: -framedrop. This will allow MPlayer not to render a frame here and there if the CPU can’t handle it. On systems that are far too slow, it won’t be a pleasure to “watch” the movie (the majority of the frames will just not be rendered at all), but on systems that are a bit faster, this will stop the playback from having hiccups here and there. You can use the -framedrop option like this:

[rechosen@localhost ~]$ mplayer -framedrop

Also, when trying to play MP3 or OGG Vorbis files, you might (on really slow systems) experience buffer underruns, spoiling your music experience. In that case, try using the libmad (in the case of an MP3) or the Tremor (in case of an OGG Vorbis) audio codec. You can detect whether you have a one or not like this:
(In case of MP3)

[rechosen@localhost ~]$ mplayer -ac help | grep mad

If the above command returns a line like this:

mad libmad working libMAD MPEG layer 1-2-3 [libmad]

Then you can play an MP3 file with libmad, which uses a lot less CPU power. To do so, invoke MPlayer like this:

[rechosen@localhost ~]$ mplayer -ac mad

In OGG’s case, you can use the same trick to look if you have a tremor audio codec available:

[rechosen@localhost ~]$ mplayer -ac help | grep tremor

Sadly, I don’t have an example of what it should look like. If you seem to have a working tremor decoder, please leave a comment here so I can add it.

Playing streams from the internet

Many web radio stations make you download a playlist with different ip’s and ports if you want to listen to them. MPlayer is perfectly able to play a web station stream, but the playlist is not a stream, nor a media file. If MPlayer doesn’t autodetect that it’s looking at a playlist and not at a direct stream or media file, you can try using the -playlist option:

[rechosen@localhost ~]$ mplayer -playlist

And if the server has hiccups and causes a lot of buffer underruns (or if you have a bad connection), you can set a bigger cache size:

[rechosen@localhost ~]$ mplayer -cache 8192 -playlist

The cache size is specified in kilobytes; the above will make MPlayer use a cache of 8 mb. Note that MPlayer doesn’t fill the whole cache before it starts playing, it only fills about 4 percent (after that it’ll try to keep filling the cache during playback). You can alter that percentage with the -cache-min option:

[rechosen@localhost ~]$ mplayer -cache 8192 -cache-min 50 -playlist

You can seek in a cache, but do not expect too much of it =).

Looping playback

If you want the media file you’re playing to loop a certain amount of times (or infinitely), you can specify the -loop option, like this:

[rechosen@localhost ~]$ mplayer -loop 3

The above command will play three times and then exit.

[rechosen@localhost ~]$ mplayer -loop 0

The above command will repeat playing forever, unless it is interrupted (for example by quitting MPlayer with the “q” keyboard shortcut). Infinite playback can be useful if you, for example, want a (promotion) movie to play all day on an exhibition.

Altering the playback speed

This may not be that useful, but it can be good for a laugh =). You can make MPlayer play a media file at a different speed with the -speed option. The value 1.0 means normal speed, 0.5 means twice as slow, 2.0 means twice as fast and so on. Specify the option like this:

[rechosen@localhost ~]$ mplayer -speed 2.0

Altering the sample rate

You might want to alter the output sample rate sometimes (certain audio cards, for example, do not support other samplerates than, say, 48000 Hz). This is done with the -srate option, like this:

[rechosen@localhost ~]$ mplayer -srate 48000

This can also be useful when exporting audio to a file (see next chapter).

Exporting the audio to a wav file

You can export the audio of a video file to a wav file this way (note that you can also use this to convert an audio file to a wav file):

[rechosen@localhost ~]$ mplayer -ao pcm

This will export the audio to the file audiodump.wav. You can also specify a filename for the exported wav:

[rechosen@localhost ~]$ mplayer -ao pcm:file=.wav

Watching a movie in ASCII

Another pretty useless but funny feature. There are two libraries that provide support for this: aa and caca. With libaa, you can only watch a movie in black & white ASCII, while libcaca supports colors. However, libaa is more widely supported. You can watch a movie with libaa this way:

[rechosen@localhost ~]$ mplayer -vo aa

And, if you want to (and can) use libcaca:

[rechosen@localhost ~]$ mplayer -vo caca

Exporting a movie to a lot of pictures

MPlayer can also export a movie to a load of images. For example:

[rechosen@localhost ~]$ mplayer -vo jpeg

Warning: the above command will output a huge amount of jpeg files. I strongly recommend to do this in a freshly made, empty directory created for this purpose.
The filenames of the jpeg file it will export will look like this:

• 00000001.jpg
• 00000002.jpg
• 00000003.jpg
• And so on…

You can export to some other formats. Just replace jpeg in the command above with ppm, png or tga. Note that all these image format have their own options, too. Look for them in MPlayer’s man page.

Specifying an aspect ratio

When playing video files on, for example, a wide laptop screen, you’ll probably want to benefit from that wideness by watching a movie in a 16:9 aspect ratio. You can do that this way:

[rechosen@localhost ~]$ mplayer -aspect 16:9

Of course, you can also specify 4:3 as the ratio to force MPlayer to show the movie in non widescreen format.

Putting options in your MPlayer config file

MPlayer has a nice way of storing options so they will be automatically set every time you invoke the MPlayer command. This can be useful if your system, for example, always needs the audio outputted with a different samplerate. However, the syntax of the config file is a little different. If you’d type -srate 48000 on the command-line, this should be specified in the config file as srate=48000. More complex options, like the -ao pcm:file=.wav, should be put between quotes in a way like this: ao=”pcm:file=.wav”. The config file is located at ~/.mplayer/config for a user, and a global configuration file is located at /etc/mplayer/config. The different values are separated by newlines, like this:

# MPlayer config file
srate=48000
ao=”pcm:file=dumpedaudio.wav”

Final words

Although this tutorial lists and explains quite a bunch of MPlayer features, this wonderful program features a lot more! Have a look at its man page or at the documentation on the MPlayer website. Anyway, I hope this tutorial helped you. Please help promoting this website a little, to let other people benefit from its growing knowledge. Thank you for reading, and happy MPlaying!

http://www.linuxuser.co.uk/tutorials/create-shared-space-for-your-multi-boot-system


Many people set up their machines to boot up into multiple Linux distributions. This may be because they are developing software that they wish to test under different distributions, or they might just be interested in trying out new distributions and seeing what they offer. One issue that comes up is that files created while you are in one distribution aren’t easily accessible once you reboot into another one.
In this tutorial, we’ll look at the steps needed to create a shared space to store your files so that you have access to them, regardless of which distribution you boot into. In this way, you will still have a separate home directory in each installation to hold all of your application settings, along with a shared data directory that will contain all of the files that you want to have access to in all of the installations.

Step by Step

Step 1 Where to set up
You will want to create a common data area that will be accessible from all of the installed OSs on your system. This could be on an external drive, like a USB key. However, this means that you would need to make sure that this external media was plugged in any time you wanted access. A better solution would be to create a partition on the internal drive to house this data area.
Step 2 Booting a live CD
Going this route means making changes to the partition table. This will require the disk partitions to be unmounted so that they can be altered. To do this, you will need to boot up from a live CD. A good first choice is SystemRescueCd. This CD will give you all of the tools you could possibly need to resize your current partitions and create a new one to hold your data directory. The easiest way to utilise it is to use UNetbootin to create a bootable USB key. There is also Parted Magic, which is one of the options available in UNetbootin.
Step 3 Resizing a partition
Most people use all of the available drive space when they install their OSs of choice, so this means that you will need to shrink at least one of the existing partitions to make space. With GParted, you can right-click on a partition and select ‘resize’.
Step 4 Resizing tip
When resizing partitions, be sure that you pick the right one. If you have a FAT or VFAT partition, be sure to defrag it first. If you end up resizing a partition on the middle of the disk, you will only be able to use the space up until the next partition.
Step 5 Creating a new partition
Once you have some free space available on your drive, you can go ahead and create a new partition to hold your data directory.
Note that there are two types of partitions: primary and logical. You can only have up to four primary partitions – so if you have more than this, you will need to make your new partition a logical one.
You can simply highlight the unused space section and click the ‘add’ icon in the top-left corner. This will pop up a dialog where you can set the size, whether it is a primary or logical partition, and what file system to format the new partition with.
Step 6 Reboot
Once you have created and formatted your new partition, you will want to write these changes to the disk and reboot back into your primary operating system or distribution.
This will then leave you ready to start using this new disk partition in all of your installed distributions.
Step 7 Creating a mount point
In order to use a disk partition, it has to be mounted to some point in your root file system. Since this will be used for your data in your regular user account, you will probably want to place it somewhere in your home directory. A good spot might be a subdirectory called my_data.
You would create this subdirectory with the following command:
mkdir ~/my_data

Step 8 Sudo
The next step is to be sure that the new partition is actually accessible. To do this, you will want to try mounting it manually.
On most Linux distributions, only the root user can do this. But, if your user account is set up as an administrator, you should have access to use the sudo command. This lets you run commands as if you were root.
Sudo will ask for your password in order to verify that it really is you.
Step 9 Manual mounting
Mounting the new partition is achieved using a single command:
sudo mount /dev/sdaX ~/my_data
…where X is the partition number of the new partition you just created.
In most cases, the mount tool is smart enough to see what file system is being used on the partition and use that. In the cases where it can’t, or you want to force it to use something else, you can hand it the ‘-t’ option and explicitly set the file system type.
Step 10 Changing ownership
When you mount a filesystem with sudo, the new subdirectory will end up being owned by root. This is not very useful to you, since you won’t be able to read or write to it. You can fix this by changing the ownership. Simply execute:
sudo chown -R jbernard.jbernard ~/ my_data
Note that you should replace ‘jbernard’ with your own username.
Step 11 Checking your mounts
You can verify your mounted partitions with the mount command. If you execute ‘mount’ with no options, it will present all of the mounted disk partitions and where on the file system these partitions are mounted to. The output for each mounted partition will look like:
/dev/sda3 on /home type ext4 (rw)
where any mount options are listed in brackets at the end.
Step 12 Unmounting
Once you are satisfied with everything, you can go ahead and unmount your data directory. You can either execute:
umount /dev/sda4
or
umount ~/my_data
You may get an error if this mount point is still in active use. For example, if you have a file browser open in the directory. Be sure to close any programs open in the data directory.
Step 13 Finding open files
Sometimes you may not realise what files are being held open, stopping you from unmounting the file system. The program lsof gives you a list of open files. You can execute:
lsof ~/my_data
to get a listing of all of the files in the subdirectory my_data that are being used by a program. This should help you identify and close down any troublesome program, and allow you to successfully unmount the data partition.
Step 14 Automating mounts
On boot, Linux looks at file ‘/etc/fstab’ to decide what partitions are to be mounted and where they are to be mounted to on the file system. This is where you will find the mount options for things like the root file system, or the home directories if they reside in their own partition. You can add a new line here for your data directory so that it too will get automatically mounted at boot time.

Step 15 Fstab options
The new line in fstab should look something like:
/dev/sda4 /home/jbernard/my_data
ext3 user,defaults 0 0
where you would enter the partition and directory names appropriate to your setup. The third field is the file system type. The fourth field is a comma-separated list of options. The two you will want to use are ‘user’ and ‘defaults’, which will set some sane defaults and also let the data partition be mounted by regular users.
Step 16 Tip about external drives
All of these instructions can be applied to an external drive, like a USB key. If you do this, you need to be sure to have it plugged in before booting. Otherwise, the system will fail to mount it and hang. You can get around this by adding ‘noauto’ to the fstab listing, but then you are responsible for remembering to plug it in before trying to use it.
Step 17 UUIDs
In step 15, we used the entry:
/dev/sda4
to identify the partition we wanted to mount. This might not work if we also use other removable media, since this could change the partition numbers that Linux uses. In these cases you can use the UUID, which is a unique identification for each device and partition. You can find it by executing
sudo vol_id -uuid /dev/sda4
You can then replace
/dev/sda4
in fstab with the entry
“UUID=xxxxxxxx”
where the Xs are the UUID alphanumeric characters of the device.
Step 18 Next system
Once you have this sorted out for the first distribution, doing the same for the other distributions is much easier. In each of the other distributions, you will need to create the same subdirectory named the same way.
You will also need to add the extra line to the file ‘/etc/fstab’. This will make your new data partition available under each of these installed distributions.
Step 19 Windows?
A lot of people also use Windows in their multi-boot systems. So what do you do? If you stick with more standard file systems, like ext2, then there are drivers and programs available that will allow you to mount this data partition and access your files.
You now have no excuse for not getting your work done, regardless of which OS you happen to be booted into. Remember that the ext3 and ext4 file systems are downwards-compatible to ext2, so they should still be available.

http://www.howtoforge.com/serving-cgi-scripts-with-nginx-on-fedora-17


This tutorial shows how you can serve CGI scripts (Perl scripts) with nginx on Fedora 17. While nginx itself does not serve CGI, there are several ways to work around this. I will outline two solutions: the first is to proxy requests for CGI scripts to Thttpd, a small web server that has CGI support, while the second solution uses a CGI wrapper to serve CGI scripts.
I do not issue any guarantee that this will work for you!

1 Preliminary Note

I'm using the website www.example.com here with the document root /var/www/www.example.com/web/; the vhost configuration is located in /etc/nginx/conf.d/www.example.com.vhost.

2 Using Thttpd

In this chapter I am going to describe how to configure nginx to proxy requests for CGI scripts (extensions .cgi or .pl) to Thttpd. I will configure Thttpd to run on port 8000.
First we install Thttpd. There is a Thttpd package for Fedora 17, but the nginx ThttpdCGI page says that Thttpd should be patched - therefore we download the src.rpm package for Fedora 17, patch it and build a new rpm package from it.
We need to install the tools that are required to build a new rpm package:
Install yum-utils (the package contains the yumdownloader tool which allows us to download a src.rpm):
Next we download the Thttpd src.rpm package for Fedora 17:
You can ignore the following warnings:
Now we download the patch to the /root/rpmbuild/SOURCES/ directory and modify the /root/rpmbuild/SPECS/thttpd.spec file accordingly:
Add the lines Patch3: thttpd-2.25b-ipreal.patch and %patch3 -p1 -b .ipreal:

[...] Patch0: thttpd-2.25b-CVE-2005-3124.patch Patch1: thttpd-2.25b-fixes.patch Patch2: thttpd-2.25b-getline.patch Patch3: thttpd-2.25b-ipreal.patch [...] %prep %setup -q %patch0 -p1 -b .CVE-2005-3124 %patch1 -p1 -b .fixes %patch2 -p1 -b .getline %patch3 -p1 -b .ipreal [...]

Now we build our Thttpd rpm package as follows:
Our Thttpd rpm package is created in /root/rpmbuild/RPMS/x86_64 (/root/rpmbuild/RPMS/i386 if you are on an i386 system), so we go there:
Install the Thttpd package as follows:
Then we make a backup of the original /etc/thttpd.conf file and create a new one as follows:

# BEWARE : No empty lines are allowed! # This section overrides defaults # This section _documents_ defaults in effect # port=80 # nosymlink # default = !chroot # novhost # nocgipat # nothrottles # host=0.0.0.0 # charset=iso-8859-1 host=127.0.0.1 port=8000 user=thttpd logfile=/var/log/thttpd.log pidfile=/var/run/thttpd.pid dir=/var/www cgipat=**.cgi|**.pl

This will make Thttpd listen on port 8000 on 127.0.0.1; its document root is /var/www.
Create the system startup links for Thttpd...
... and start it:
Next create /etc/nginx/proxy.conf:

proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; client_max_body_size 10m; client_body_buffer_size 128k; proxy_connect_timeout 90; proxy_send_timeout 90; proxy_read_timeout 90;

Now open your vhost configuration file...
... and add a location /cgi-bin {} section to the server {} container:

server { [...] location /cgi-bin { include proxy.conf; proxy_pass http://127.0.0.1:8000; } [...] }

Reload nginx:
Because Thttpd's document root is /var/www, location /cgi-bin translates to the directory /var/www/cgi-bin (this is true for all your vhosts, which means each vhost must place its CGI scripts in /var/www/cgi-bin; this is a drawback for shared hosting environments; the solution is to use a CGI wrapper as described in chapter 3 instead of Thttpd).
Create the directory...
... and then place your CGI scripts in it and make them executable. For testing purposes I will create a small Hello World Perl script (instead of hello_world.cgi you can also use the extension .pl -> hello_world.pl):

#!/usr/bin/perl -w # Tell perl to send a html header. # So your browser gets the output # rather then (command line # on the server.) print "Content-type: text/html\n\n"; # print your basic html tags. # and the content of them. print "\n"; print " Hello world \n";

Open a browser and test the script:
If all goes well, you should get the following output:

http://www.howtoforge.com/sharing-terminal-sessions-with-tmux-and-screen


tmux and GNU Screen are well-known utilities which allow multiplexing of virtual consoles. Using either, it is possible to start a session, detach, move to a different machine and resume the session in uninterrupted progress. It's also possible to use these tools to share a single session between more than one user at the same time.

Basic Sharing with a Single Account

If an account is held jointly between two or more users, then the sharing of the terminal console is very simple. Neither tmux nor screen require anything out of the ordinary for basic sharing between a single account logged in multiple times. Basic sharing is very easy if you are both logged in as the same user.

Basic sharing with screen

In one terminal create a new session for screen, where foobar is the name of your screen session:
Then in the other terminal, attach to that session.
That's it, there were just two steps.

Basic sharing with tmux

Again, there are only two steps. In the first terminal, start tmux where shared is the session name:
Then in the second terminal attach to the shared session.
That's it.

Sharing Between Two Different Accounts

Sharing between two different accounts requires some additional steps to grant the privileges necessary for one account to access another's session. In some cases, it will require help from the system administrator to prepare the setup.

Sharing between two different accounts with tmux

For different users, you have to set the permissions on the tmux socket so that both users can read and write it. There is only one prerequiste, that there be a group in common between the two users. If such a group does not exist it will be necessary to create one.
In the first terminal, start tmux where shared is the session name and shareds is the name of the socket:
Then chgrp the socket to a group that both users share in common. In this example, joint is the group that both users share. If there are other users in the group, then they also have access. So it might be recommended that the group have only the two members.
In the second terminal attach using that socket and session.
That's it. The session can be made read-only for the second user, but only on a voluntary basis. The decision to work read-only is made when the second user attaches to the session.

Sharing between two different accounts with screen

If you are logged in as two different users, there are three prerequisites to using screen. First, screen must be set SUID and it is necessary to remove group write access from /var/run/screen. The safety of using SUID in this context is something to consider. Then you must use screen's ACLs to grant permission to the second user.
In the first user's terminal, start screen as in the basic sharing above, where foobar is the name of the screen session. Then turn on multiuser mode and add user2 to the ACL, where user2 is the second account to be sharing the session.
The session can be made read-only for the second user by entering the following ACL change: ^A:aclchg user2 -w "#?"
Then in the other terminal, attach to the first user's session.
It is also possible to put multiuser on and acladd user2 into .screenrc to have it take effect automatically upon starting screen. If the changes are not desired in all screen sessions, then a separate .screenrc configuration file can be specified by using the -c option when starting screen.

Afterthought

Be careful when exiting. If you just exit the shell, it will end the terminal session for all parties. If you instead detach the session then the other user can continue working uninterrupted. In tmux that is ^B-d and in screen that is ^A-d

http://www.linuxjournal.com/content/experimental-animation-and-video-techniques-linux


 Animation and video editing in Linux can be treacherous territory. Anyone who has tried working in these media probably has experienced the frustration of rendering a huge file for an hour only to see the program crash before the export is finished. A bevy of tools and applications for manipulating video exist for Linux, and some are more mature than others.
The most mainstream of GUI applications have been covered quite a bit in other Linux-related articles on the Web and in print, including in previous issues of Linux Journal. Some of these names may ring familiar to you: Kino, PiTiVi, Openshot, Cinelerra, Kdenlive and Open Movie Editor.
Although I refer to these nonlinear editors (NLEs) from time to time here, the main purpose of this article is to introduce some video effects and techniques you may not have thought of before. If you are producing a film or animation in a conventional format, such as a DVD or a Web video, you most likely will want to employ a suitable NLE at some point in your process. Many of the ideas I present in this article are experimental.

Video Editing

LiVES
LiVES is primarily a VJ (video jockey) tool for performing live audio-visual effects, but it also can encode and export video via its MPlayer back end. The interface has two modes: clip editor and multitrack editor. The clip editor view is more suitable for live VJ sets, while you'll probably lean toward the multitrack view if using LiVES as your NLE.
Figure 1. LiVES in the Clip Editor View
LiVES is highly extensible. In addition to the built-in effects, you can apply custom RFX (rendered/real-time effects) plugins. Several of these scripts are available for download from the LiVES Web site. You also can share LiVES' real-time effects with other applications using the frei0r effects API.
The number of options and the advanced effects in LiVES are comparable to those of Cinelerra, but I strongly recommend LiVES over the latter. Cinelerra is indeed a powerful video editor, but the interface is antiquated and difficult to use. Although LiVES can seem foreign to new users, it is not hard to become acquainted with it.
ZS4
ZS4, formerly known as Zweistein, is a unique—and quite strange—video editor and compositor. The developers of ZS4, who go by the name "t@b", are a duo of musicians who use their own software to create music videos. They are hard to pinpoint on the Web, as they use several sites for different purposes.
I admit that I was confused by the existence of both zs4.net and zs4.org, as well as the Viagra advertisement lines that appeared in Google search results at the zs4.net domain. The two sites both contain download links for ZS4 as well as some other software.
If you plan to use ZS4, I recommend downloading the t@b Media Converter and/or installing Avidemux, as ZS4 is picky about importing video files. Most videos are not compatible out of the box, so it may be necessary to convert them to a format ZS4 can work with.
Working with ZS4 can be frustrating at first because the interface is far from intuitive. Menus are not where you would expect them to be, and you might find yourself aimlessly clicking your cursor in different places to accomplish a simple task, such as dragging a media file into the timeline. The media viewing windows are vaguely labeled "rectangles". To show or hide a track, you click on + or - instead of the typical open- or closed-eye icon.
It took me years to gather the patience to learn my way around this program. So yes, the GUI needs some serious work if it ever is going to reach a mass audience, but it doesn't seem like mainstream appeal is a major concern for the eccentric-minded developers.
So, why tell you about a bizarre-looking application that hasn't been updated in years when there are plenty of other video editors for Linux? Well, for all ZS4's graphical quirks, it can accomplish some very interesting compositing effects.
Figure 2. Tiling Effects in ZS4

 Animation

GIMP
The famous GNU Image Manipulation Program can create animations as well as still images. Because it is a full-featured image editing program, you can use it to create an animation entirely from scratch.
In order to import a prepared image sequence into GIMP, click File→Open as Layers... or press Ctrl-Alt-o. The Open Image dialog allows you to select multiple files, which then will appear as layers.
Figure 3. An animation in progress that I made by tracing reference photos of faces from the Psychological Image Collection at Stirling (PICS).
In the example shown in Figure 3, I imported a series of reference photos into GIMP and traced over them in cyan and then in black. I eventually deleted the reference photos and blue layers, leaving only the black-lined drawings that I planned to use for my final animation.
To finish my animation, I exported the layers as a GIF and specified animation parameters in the export dialog. Because I wanted to use the animation in a video, I had to turn the animated GIF into a video file. I ultimately chose to do this by way of screen recording, but that is not the only option.

From Stills to Movies

Let's say you have a sequence of images, or perhaps an animated GIF, that you want to make into a video file. There are several ways to go about this.
Stopmotion
Stopmotion started as a student project under the Skolelinux/Debian-edu organization in 2005. Although it hasn't been updated since 2008, I find it to be a handy tool for anyone working with frame-by-frame animation. You might have trouble finding Stopmotion in your distribution's repositories if you aren't using a DEB- or RPM-based package manager, but you can, of course, compile it from source on any distribution; that's how I set it up in Sabayon Linux.
Stopmotion is simple and to the point, with a nice drag-and-drop interface. It's not designed for heavy post-production or for drawing and adding effects to frames. Rather, the point is to give users an easy way to arrange images sequentially and export them into a video file.
The video import and export options are limited only by your imagination (and your knowledge of the command line). If you know how to use FFmpeg and/or MEncoder to convert image sequences to video, you can pass your desired command-line arguments to Stopmotion, which is essentially a GUI for those programs. Stopmotion also gives you several choices of video capture commands for grabbing video from your Webcam or another attached device.
One cool feature I didn't know about until I read the user's handbook was the option to add sound. You can set a sound clip to start at any given frame by double-clicking on it. The audio I added to my sequence didn't play in the exported AVI, but maybe you'll have better luck.
If you want to perform more-advanced editing on your individual frames, Stopmotion has a button to open a selected frame in GIMP. You also can export your data into Cinelerra for video editing.
Figure 4. Animating a Sequence of Faces in Stopmotion