28 Nov 2011 Switching to a graphical login on RHEL6
This is a short post on how to install the necessary components to get X Server running on a bare bone RedHat 6 Enterprise Server (CentOS6) installation.
The following commands should be run from a console window as the root user.
Install barebone X support
# yum groupinstall "X Window System"
Install X and the Gnome Environment
# yum groupinstall "X Window System" "GNOME Desktop Environment"
Install X and the KDE Window System
# yum groupinstall "X Window System" KDE
Install the XFCE desktop environment
# yum groupinstall "X Window System" XFCE
When you have chosen your desired desktop environment, make the final change to make the Gnome Display Manager show you a logon screen.
Edit the file /etc/inittab and change the line
from
id:3:initdefault:
to
id:5:initdefault:
You will be greeted with a graphical logon screen the next time you have rebooted your server.
Tags: CentOS, KDE, rhel6, X, XFCE
Posted by Hans-Henry Jakobsen
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!
Tags: dd
Posted by Hans-Henry Jakobsen
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/_//' *
Tags: rename
Posted by Hans-Henry Jakobsen
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.
Tags: 11.04, alsamixer, howto, Ubuntu
Posted by Hans-Henry Jakobsen
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 10:41Windows
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.
Posted by Hans-Henry Jakobsen
