Posted on January 18, 2010 by Ahmed Tawfik

How to unset environment variables in Bash

use the keyword unset :), that’s it!

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Change display resolution in Redhat 5 or Oracle Enterprise Linux 5

Posted on January 9, 2010 by Ahmed Tawfik

Edit your “/etc/X11/xorg.conf” file, add the “Modes” part under subsection “Display” where the first mode – which is 1024×768 in the example below – will be the default one:

Section "Screen"
        Identifier "Screen0"
        Device     "Videocard0"
        DefaultDepth     24
        SubSection "Display"
                Viewport   0 0
                Depth     24
                Modes     "1024x768" "800x600" "640x480"
        EndSubSection
EndSection


Save the file, then restart your X server or restart your computer if you don’t know how to 🙂

Source

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Temporary workaround for virtualbox not able to unmount CD/DVD drive or ISO image

Posted on January 8, 2010 by Ahmed Tawfik

Just don’t use  a dynamic expanding harddisk and the problem is gone!!

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Regenerate Database Console Repository

Posted on January 6, 2010 by Ahmed Tawfik

This is needed in case you misconfigured your Database console, you should rebuild it by doing the following:

  1. Drop it: “emca -deconfig dbcontrol db -repos drop“
  2. Recreate it: “emca -config dbcontrol db -repos create”

That’s it, should be fine now :), thanks to this great post

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How to solve the problems of "Oracle Enterprise Linux" in virtualbox

Posted on January 6, 2010 by Ahmed Tawfik

Not able to boot:
Just press escape during the grub loading process and choose the second kernel :), that’s it! If you want it to be persistent to avoid doing that at every startup, just go edit the “/boot/grub/grub.conf” and change “default=0” to “default=1” to point to the second kernel automatically.

Source

Not able to install Guest Additions:

  1. mount the installation DVD, navigate to the folder “Server” and issue the command “rpm -ivh kernel-devel-2.6.18-164.el5.i686.rpm”
  2. unmount the DVD (if you’re not able to unmount due to a bug in virtualbox that prevents unmounting, just shutdown the guest OS and then remove it from the storage section)
  3. In the guest OS, click “Devices”->”Install Guest Additions”
  4. The CD will be mounted, navigate to its folder (in /media/VBox***) and run “sh VBoxLinux***x86.sh” (x86 here if you’re using 32-bit edition)
  5. Reboot and enjoy 🙂

Some other issues I encountered while installing guest additions for Oracle Enterprise Linux 5.6 32-bit, you have to install gcc also, and in order to do so, you have to install the following packages from the DVD:  glibc-devel*, glibc-headers*

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