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14 Nov 2011 How to corrupt a disk partition using dd

I wanted to test corruption of a 41TB XFS filesystem and the dd command was the perfect tool for the job.
I used a block size of 512 bytes and wrote 10 blocks of data from device /dev/urandom to the partition /dev/sdb1.
The “Seek” option specifies how many blocks are skipped, counting 100 blocks from the beginning of the partiton, before writing the random/corrupted data.

# dd bs=512 count=10 seek=100 if=/dev/urandom of=/dev/sdb1

Caution!
This procedure WILL most likely corrupt your disk partition or files on the partition. Use it ONLY on test systems and with a valid backup!

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10 Nov 2011 Remove white space from file names

This is a one liner to remove white space in filenames using a linux console

# rename 'y/ /_/'  *

You could also do this the other way, remove underscore with space

# rename 'y/_//' *

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19 Sep 2011 Fix low volume issue in Ubuntu 11.04

This post is a short howto to fix/workaround the problem with low volume in some Ubuntu 11.04 installations.
The fix for me was to open a console window (as the user I’m logged in with) and start the alsamixer

# alsamixer

You will then see the alsamixer window. Use the left/right arrow keys and choose the device you would like to configure. In my case it was the headphone.

Choose which sound card you would like to configure on the headphone by pressing the F6-key. Make your choice and press the Enter-key.

Use your up/down arrow keys to choose the right volume for your configuration. You should have some audio playing while you configure to determine the right value.

Press the Esc key to exit alsamixer when you have found the right volume. Your settings are persistent and will survive a reboot.

You are now done with configuring your sound card.

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14 Sep 2011 Windows grep command alternative

grep is a linux console command to print lines matching a line, but Windows does not have the grep command.
In Windows you have to use the findstr command in a console window.

Example

C:\>dir |findstr Windows
13.09.2011  10:41              Windows

The findstr command is default case sensitive just like in linux.

findstr options

C:\>findstr -?
Searches for strings in files.

FINDSTR [/B] [/E] [/L] [/R] [/S] [/I] [/X] [/V] [/N] [/M] [/O] [/P] [/F:file]
        [/C:string] [/G:file] [/D:dir list] [/A:color attributes] [/OFF[LINE]]
        strings [[drive:][path]filename[ ...]]

  /B         Matches pattern if at the beginning of a line.
  /E         Matches pattern if at the end of a line.
  /L         Uses search strings literally.
  /R         Uses search strings as regular expressions.
  /S         Searches for matching files in the current directory and all
             subdirectories.
  /I         Specifies that the search is not to be case-sensitive.
  /X         Prints lines that match exactly.
  /V         Prints only lines that do not contain a match.
  /N         Prints the line number before each line that matches.
  /M         Prints only the filename if a file contains a match.
  /O         Prints character offset before each matching line.
  /P         Skip files with non-printable characters.
  /OFF[LINE] Do not skip files with offline attribute set.
  /A:attr    Specifies color attribute with two hex digits. See "color /?"
  /F:file    Reads file list from the specified file(/ stands for console).
  /C:string  Uses specified string as a literal search string.
  /G:file    Gets search strings from the specified file(/ stands for console).
  /D:dir     Search a semicolon delimited list of directories
  strings    Text to be searched for.
  [drive:][path]filename
             Specifies a file or files to search.

Use spaces to separate multiple search strings unless the argument is prefixed
with /C.  For example, 'FINDSTR "hello there" x.y' searches for "hello" or
"there" in file x.y.  'FINDSTR /C:"hello there" x.y' searches for
"hello there" in file x.y.

Regular expression quick reference:
  .        Wildcard: any character
  *        Repeat: zero or more occurrences of previous character or class
  ^        Line position: beginning of line
  $        Line position: end of line
  [class]  Character class: any one character in set
  [^class] Inverse class: any one character not in set
  [x-y]    Range: any characters within the specified range
  \x       Escape: literal use of metacharacter x
  \    Word position: end of word

For full information on FINDSTR regular expressions refer to the online Command
Reference.

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29 Aug 2011 Configure miniDLNA on Ubuntu 11.04

This is a short HOWTO on installing and configuring miniDLNA on Ubuntu 11.04 Natty to work with my Sony Bravidia KDL-40EX711 LED TV.
First we need to install the minidlna software.

# sudo aptitude install minidlna

The content of my /etc/minidlna.conf file

port=8200
network_interface=eth0
media_dir=P,/export/pictures
friendly_name=My DLNA Server
album_art_names=Cover.jpg/cover.jpg/AlbumArtSmall.jpg/albumartsmall.jpg/AlbumArt.jpg/albumart.jpg/Album.jpg/album.jpg/Folder.jpg/folder.jpg/Thumb.jpg/thumb.jpg
inotify=yes
enable_tivo=no
strict_dlna=no
notify_interval=900
serial=12345678
model_number=1

Comments in the config file has been removed to reduce the listing.

The media_dir variable can be configured four ways:
A – Audio
V – Video
P – Pictures
No value – You have to browse the folders to determine the type of content

I used the P value in the example above to indicate that the folder contains pictures.
You can add several media_dir variables to point to different folders.

Start the miniDLNA daemon

# sudo /etc/init.d/minidlna start

The media database will be built the first time you start the miniDLNA daemon and can take some time depending on the folder size.

You should now have access to your newly configured DLNA server on your TV by pressing the Home button.
Choose Photo and scroll down to the penguin icon named “My DLNA Server”, ref variable friendly_name in the config file.

The default location for the logfile is /var/log/minidlna.log and it can be useful for debugging if you have problems with miniDLNA.
If you think you have problems with the minidlna database, you can rebuild the mediadatabase by issuing this command

# sudo /usr/sbin/minidlna -f /etc/minidlna.conf -R -d

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