Tuesday, March 9, 2010

HOW TO MOUNT USB DEVICE LINUX

USB storage devices have the enormous advantage that for the most part they use a standard set of protocols. Thus, instead of needing individual drivers, as does much computer hardware, a standard driver permits access to the devices, making them very portable and able to easily work on many platforms.

Automounting

Mounting

By default, storage devices that are plugged into the system mount automatically in the /media directory, open a file browser window for each volume and place an icon on your desktop. If you plug in a usb hard disk with many partitions, all of the partitions will automatically mount. This behaviour may not be what you want so you can configure it as shown below.

If the volumes have labels the icons will be named accordingly, otherwise they will be named "disk" and as more volumes are added, you can get "disk-1" and so on.

To change the volume label see RenameUSBDrive.

Configuring Automounting

To enable or disable automount open a terminal and type gconf-editor followed by the [Enter] key.

Browse to /apps/nautilus/preferences/media_automount.

The media_automount key controls whether to automatically mount media. If set to true, then Nautilus will automatically mount media such as user-visible hard disks and removable media on start-up and media insertion.

There is another key /apps/nautilus/preferences/media_automount_open. This controls whether to automatically open a folder for automounted media. This key can also be set in the Nautilus (file manager) window. From the Edit menu in Nautilus select Preferences and then select the Media tab.

If set to true, then Nautilus will automatically open a folder when media is automounted. This only applies to media where no known x-content/* type was detected; for media where a known x-content type is detected, the user configurable action will be taken instead. This can be configured as shown below.

Configuring Program Autostart

To control which programs automatically start when you plug in a device, go to System->Preferences->Removable Drives and Media.

Ubuntu 9.10 (Karmic Koala)

In Ubuntu 9.10 (Karmic Koala) Removable Drives and Media is no longer in the Preferences menu but you can still do this as follows.

This user configurable action for specific media types can be configured in the Nautilus (file manager) window. From the Edit menu in Nautilus select Preferences and then select the Media tab. There you can select what happens when media is inserted. For example we need to turnoff audio CD auto play. CD audio "can do nothing" or "ask what to do" or "open folder".

For more complex scenarios, see UsbDriveDoSomethingHowto.

Unmounting/Ejecting

Before you disconnect the device, don't forget to unmount it. This can be done by right clicking the desktop icon and selecting "Unmount" (or in some cases, "Eject"). In Ubuntu 9.10 (Karmic Koala), in the file manager window you can also click on an "eject" button against the name of the mounted volume.

Automounting (Ubuntu Server)

By default, disk drives do not automount in Ubuntu Server Edition. If you are looking for a lightweight solution that does not depend on HAL/DBUS, you can install "usbmount".

Manually Mounting

Using mount

Get the Information

IconsPage/IconGNOMETerminal.png Sometimes devices don't automount, in which case you should try to manually mount it. First, you must know what device we are dealing with and what filesystem it is formatted with. Most flash drives are FAT16 or FAT32 and most external hard disks are NTFS.

sudo fdisk -l

Find your device in the list, it is probably something like /dev/sdb1. For more information about filesystems, see LinuxFilesystemsExplained.

Create the Mount Point

Now we need to create a mount point for the device, let's say we want to call it "external". You can call it whatever you want, just please don't use spaces in the name or it gets a little more complicated - use an underscore to separate words (like "my_external"). Create the mount point:

sudo mkdir /media/external

Mount the Drive

IconsPage/example.png We can now mount the drive. Let's say the device is /dev/sdb1, the filesystem is FAT16 or FAT32 (like it is for most USB flash drives), and we want to mount it at /media/external (having already created the mount point):

sudo mount -t vfat /dev/sdb1 /media/external -o uid=1000,gid=100,utf8,dmask=027,fmask=137

The options following the "-o" allow your user to have ownership of the drive, and the masks allow for extra security for file system permissions. If you don't use those extra options you may not be able to read and write the drive with your regular username.

Otherwise if the device is formatted with NTFS, run:

sudo mount -t ntfs-3g /dev/sdb1 /media/external

IconsPage/IconNote.png You must have the ntfs-3g driver installed. See MountingWindowsPartitions for more information.

Unmounting the Drive

IconsPage/example.png When you are finished with the device, don't forget to unmount the drive before disconnecting it. Assuming /dev/sdb1 mounted at /media/external, you can either unmount using the device or the mount point:

sudo umount /dev/sdb1

or:

sudo umount /media/external

You cannot unmount from the desktop by right clicking the icon if the drive was manually mounted.

Using pmount

There is a program called pmount available in the repositories which allows unprivileged users to mount drives as if they were using sudo, even without an entry in /etc/fstab. This is perfect for computers that have users without RootSudo access, like public terminals or thin clients.

pmount can be used with the same syntax as mount (but without sudo), or quite simply as follows:

pmount  [ label ] 

Example:

  •  pmount /dev/sdb1 flash_drive
    This will mount the device /dev/sdb1 at /media/flash_drive

If you leave off the label option, it will mount by default at /media/device

To unmount the device, use pumount, like so:

pumount 

Example:

  •  pumount /dev/sdb1

For more help, you can see the man pages for pmount and pumount.

Unmounting Explained

IconsPage/IconHint2.png Before disconnecting devices, you must unmount them first. This is similar to "Safely Remove" in Windows in that the device won't unmount until data is finished being written to the device, or until other programs are finished using it. This applies to all types of storage devices, including flash drives, flash cards, external hard drives, ipods and other media players, and even remote storage like Samba or NFS shares.

Failure to unmount before disconnecting the device can result in loss of data and/or a corrupted file system. There are no exceptions to this rule. Be safe - unmount your drives before disconnecting them!

Other Useful Commands

To see a list of your USB devices (the vendor and device ID's), run:

lsusb

To see all attached storage devices and their partitions, run:

sudo fdisk -l

To see information about currently mounted systems, simply run:

mount

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Monday, March 8, 2010

How to use Mencoder to encode videos

With personal media players (PMP) getting really affordable, consumers are converting their video collection to formats that are supported by their favorite PMP. In my case, I use an iPhone so I convert movies to H.264 or MP4 formats.

There are several tools available to convert videos to other formats and mencoder is just one of them. Personally, I use ffmpeg, also from the same family as mencoder but with a graphical front-end. Anyway, to those who want to convert videos using the CLI,here's useful linux tips for you..

Video conversion with mencoder

Mencoder is part of the MPlayer media player package. While MPlayer can play audio and video files, mencoder converts and manages multimedia files. The application has a ton of graphical user interfaces, but you can use it from the command line to produce video files in almost any format you want. Here's how.

Among the file types mencoder can handle are MPEG/VOB, AVI, ASF/WMA/WMV, RM, QT/MOV/MP4, Ogg/OGM, MKV, VIVO, FLI, and FLV. The command syntax is straightforward despite a wealth of options. There's little mencoder can't do when it comes to multimedia conversion.

Here's a simple command that converts an MPG file to AVI format:

mencoder file.mpg -o file.avi -ovc lavc -oac lavc
-ovc and -oac represent the options for the video and audio codecs that mencoder will use. To find out what video codecs are installed on your system, use mencoder -ovc help and mencoder -oac help.

Suppose you need a file with no compression on the audio part and decide to use PCM. You can specify the type of audio codec you want by using the acodec option:

mencoder file.mpg -o file.avi -ovc lavc -oac lavc -lavcopts acodec=pcm

When it comes to MP3 compression, you can also choose a bitrate using abitrate:

mencoder file.mpg -o file.avi -ovc lavc -oac lavc -lavcopts acodec=libmp3lame:abitrate=128

You can use lameopts if you have libmp3lame installed and want to add extra options to the encoding process. You can also create files with variable bit rate audio compression:

mencoder file -o file.avi -ovc lavc -oac mp3lame -lameopts vbr=2:q=3

where q can be any number between 0 and 9.

You can do the same thing with the video part of the file:

mencoder file.mpg -o file.avi -ovc lavc -oac lavc -lavcopts acodec=libmp3lame:abitrate=128 vcodec=xvid

If you don't want to use video compression, try vcodec=copy. With that option, the frames will be copied one by one from the source file.

You can use xvid or divx directly, without going through lavc:

mencoder -ovc xvid -oac mp3lame -o destination.avi source.avi

If you need customized quality, you can add a few options to the XviD compression:

mencoder -ovc xvid -oac mp3lame -xvidencopts bitrate=878 -o destination.avi source.avi

The higher the bitrate, the better quality the video file will be. The downside is a larger file size.

Now let's get fancy and make an XviD copy of a DVD using two passes. During the first pass, mencoder analyzes the content of the file; on the second pass mencoder encodes the new file based on the information obtained. By using two passes you can produce a better compressed file, but you'll have to wait a little longer for it, and you'll probably see CPU usage at 90% during the conversion:

mencoder dvd:// -oac mp3lame -ovc xvid -xvidencopts pass=1 -o /dev/null

mencoder dvd:// -oac mp3lame -ovc xvid -xvidencopts pass=2:bitrate=800 -o xvidfile.avi

You can use whatever bitrate option you want. If you need to squeeze a DVD into a 700MB XviD file, you could use the following command, which forces the file size of the resulting AVI to 700MB.:

mencoder dvd:// -ovc xvid -oac mp3lame -xvidencopts bitrate=-700000 -o file.avi

If you don't like the CPU being used to the max and want to leave resources for launching other applications, use the nice option, which will run the program with the lowest priority when it comes to process scheduling:

nice -n 19 mencoder dvd:// -ovc xvid -oac mp3lame -xvidencopts bitrate=-700000 -o file.avi

Suppose you have a folder full of small video files of different types and would like to merge them into one big movie for easy watching. First, rename them so that they're in the order you want them to appear in the final video, then use:

mencoder * -o output.avi

If you want to add a particular audio file to a movie, use:

mencoder source.avi -o destination.avi -ovc copy -oac mp3lame -audiofile file.wav (for uncompressed files)

mencoder source.avi -o destination.avi -ovc copy -oac copy -audiofile file.mp3 (for compressed files)

To convert a video file to run on a device running iPodLinux, use:

mencoder -ovc raw -ofps 15 -oac pcm -vf scale=176:-2,expand=176:132,format=bgr16 input.file -o output.avi

This produces a RAW AVI file with uncompressed audio data and scales it so it fits the Nano's tiny screen perfectly.

I have a Pocket PC that I sometimes bring with me on business trips. I take a couple of movies I haven't seen in a while and convert them to fit on a 512MB SD card:

mencoder -oac mp3lame -lameopts mode=3:preset=24 -ovc lavc -lavcopts vcodec=mpeg4:vhq:vbitrate=384:keyint=250 -vop expand="320:240" -o outputfile.avi inputfile.avi

or

mencoder input.avi -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=200:abitrate=48 -vop scale=320:240 -oac copy -o output.avi

The difference here is that the latter command scales the file and the former fills the PDA's 320x240-pixel screen with the movie.

If you have a webcam and want to record the output, use:

mencoder tv:// -tv driver=v4l:device=/dev/video0:width=640:height=480:forceaudio -ovc lavc -oac lavc -lavcopts vcodec=mpeg4:acodec=mp3 -ffourcc divx -o test.avi

The command records anything output by /dev/video0 in 640x480 resolution, using DivX with MP3 audio as an output result.

As you can see, you can use mencoder to convert almost any type of video file in several ways. It works fast, it works well, and I wouldn't change it for any other application, be it GUI-friendly or not.

example pic made by me

Sunday, March 7, 2010

Convert images with open source ImageMagick

Tools like the GIMP (www.gimp.org) and similar graphical applications are great for modifying and manipulating images. Sometimes, however, they can be overkill for little things that need to be done, such as converting file types or resizing images. As well, a graphical tool can be time consuming and difficult to script, unlike CLI tools.

The ImageMagick suite (www.imagemagick.org) of programs allows you to manipulate images from the command-line, making it much simpler to convert large numbers of pictures or even for that single quick image conversion.

Some of the tools that ImageMagick includes are the convert tool, the composite tool, and the display tool.

The convert tool is used to convert pictures from one format or size to another. The easiest method is to simply convert an image from one format to another using:

$ convert image.jpg image.png

This will convert image.jpg from a JPEG to a PNG and save it as image.png. To convert and resize an image, use:

$ convert -size 50x50 image.jpg image.png

This will convert from JPEG to PNG format and resize the resulting image to 50x50 pixels. Likewise, you can use convert to rotate an image:

$ convert -rotate 90 image.jpg image.png

This will rotate the image 90 degrees and convert it to a PNG file. To manipulate the file and keep it in the same format:

$ convert -rotate 90 image.jpg image-new.jpg

To create a composite image, or layer one image above another, use the composite tool. For instance, to put logo.jpg in the top-left corner of image.jpg, you would use:

$ composite -gravity NorthWest logo.jpg image.jpg composite.jpg

This will layer logo.jpg over image.jpg in the top-right corner (NorthWest), and the resulting file will be named composite.jpg. Each edge of the picture is noted by direction: Top is North, bottom is South, right is East, and left is West. The composite tool respects transparent pixels, so using it is a great way to automatically tag all your photos with your name or Web site address.

These commands merely scratch the surface of what ImageMagick can do. ImageMagick is capable of creating new images, embedding steganography in pictures, and much more.

WHY LINUX BETTER THAN WINDOWS












Friday, March 5, 2010

LIST OF KEYBOARD SHORTCUTS WINXP

General keyboard shortcuts

* CTRL+C (Copy)
* CTRL+X (Cut)
* CTRL+V (Paste)
* CTRL+Z (Undo)
* DELETE (Delete)
* SHIFT+DELETE (Delete the selected item permanently without placing the item in the Recycle Bin)
* CTRL while dragging an item (Copy the selected item)
* CTRL+SHIFT while dragging an item (Create a shortcut to the selected item)
* F2 key (Rename the selected item)
* CTRL+RIGHT ARROW (Move the insertion point to the beginning of the next word)
* CTRL+LEFT ARROW (Move the insertion point to the beginning of the previous word)
* CTRL+DOWN ARROW (Move the insertion point to the beginning of the next paragraph)
* CTRL+UP ARROW (Move the insertion point to the beginning of the previous paragraph)
* CTRL+SHIFT with any of the arrow keys (Highlight a block of text)
* SHIFT with any of the arrow keys (Select more than one item in a window or on the desktop, or select text in a document)
* CTRL+A (Select all)
* F3 key (Search for a file or a folder)
* ALT+ENTER (View the properties for the selected item)
* ALT+F4 (Close the active item, or quit the active program)
* ALT+ENTER (Display the properties of the selected object)
* ALT+SPACEBAR (Open the shortcut menu for the active window)
* CTRL+F4 (Close the active document in programs that enable you to have multiple documents open simultaneously)
* ALT+TAB (Switch between the open items)
* ALT+ESC (Cycle through items in the order that they had been opened)
* F6 key (Cycle through the screen elements in a window or on the desktop)
* F4 key (Display the Address bar list in My Computer or Windows Explorer)
* SHIFT+F10 (Display the shortcut menu for the selected item)
* ALT+SPACEBAR (Display the System menu for the active window)
* CTRL+ESC (Display the Start menu)
* ALT+Underlined letter in a menu name (Display the corresponding menu)
* Underlined letter in a command name on an open menu (Perform the corresponding command)
* F10 key (Activate the menu bar in the active program)
* RIGHT ARROW (Open the next menu to the right, or open a submenu)
* LEFT ARROW (Open the next menu to the left, or close a submenu)
* F5 key (Update the active window)
* BACKSPACE (View the folder one level up in My Computer or Windows Explorer)
* ESC (Cancel the current task)
* SHIFT when you insert a CD-ROM into the CD-ROM drive (Prevent the CD-ROM from automatically playing)
* CTRL+SHIFT+ESC (Open Task Manager)