Can not boot to X11 after remove tcp_wrappers-libs-7.6-57.el6.rfx.x86_64

When I tried to install skype according to
http://www.if-not-true-then-false.com/2012/install-skype-on-fedora-centos-red-hat-rhel-scientific-linux-sl/

there is a conflict on tcp_wrappers-libs   which also uninstall about 900mb files. Since there are some files that are in version 6.2 and 6.3, I decided to uninstall all of those.
However, after doing that I found:

1. system can not boot X11
2. dhcp can not work
3. most of the softerware is gone for example gedit vlc kde, etc. 

At the very beginning, I thought it is due to improper nvidia problem, as not booting to X11 is usually due to that. However, this time I can not do that. Therefore, I check 

#less /etc/log/xorg.0.log

where [EE] means error. but still I couldn't get the problem solved. 

later on I use 

#dhclient

to make internet work

and after searching, I found all the things were actually uninstalled. To get them back, I did

# yum grounpinstall "X Window System"
# yum grounpinstall "Desktop"
# yum grounpinstall "Desktop Platform"
# yum grounpinstall "KDE Desktop"

then everything goes back to normal. what a disaster!!

some usefull command
# yum grouplist     
shows all the group names
# service NetworkManager stop (start)

enable numlock after boot in scientific linux

1. Install "numlockx" either by compile it or find its repo (now i can not find any repo that has it)
2. Edit the /etc/gdm/Init/Default file

Install numlockx through terminal using this command
sudo yum install numlockx

Edit the /etc/gdm/Init/Default file through Gedit using this command in a terminal
sudo gedit /etc/gdm/Init/Default

In the file which opens, above exit 0, paste the lines below

if [ -x /usr/bin/numlockx ]; then
/usr/bin/numlockx on
fi

Save the file and exit.

Next time you reboot, num lock will be on by default

autostart mount cifs after networkmanager is working

I need to connect to a samba server everytime when eth0 started. To do that, I firstly wrote script into

/etc/fstab

However, it doesn't work. it is actually because the network hasn't been initiallized.

so I decided to put

mount -t cifs //file.eait.uq.edu.au/username /home/chenming/Hdrive -o username=username,password="pass",domain=UQ,rw,nounix,iocharset=utf8,file_mode=0777,dir_mode=0777,gid=1000,uid=1000

into

 /etc/sysconfig/network-scripts/ifup   or ifup-eth

but it seems not working either.


Finally, the method works by putting

mount -t cifs //file.eait.uq.edu.au/username /home/chenming/Hdrive -o username=username,password="pass",domain=UQ,rw,nounix,iocharset=utf8,file_mode=0777,dir_mode=0777,gid=1000,uid=1000

in

/etc/NetworkManager/dispatcher.d/hdrive

and change hdrive into executable. now it works like a charm

Virtualbox asks to run /etc/init.d/vboxdrv setup every time for my debian 2.6.32-5-amd64

I tried many things on the web, like uninstall virtualbox-4.2, dkms, linux-headers-"uname -r"
I still can not make it work.

in a way

what i found instead is that if you run

# modprobe vboxdrv

before running virtualbox, you will not have that sign

so I just add

 vboxdrv 

in /

 /etc/modules

which is equivalent to run

  'modprobe vboxdrv' 

after system start

delete the start up applications that are not listed in xfce

it is found that in xfce some of the auto start application are not listed on the start up session. to remove these applications. you can delete all the files at /home/user/.cache/sessions/

boot problem after update debian 2.6.32.5-amd64

This time it happens on my laptop Toshiba. after
# apt-get upgrade
after rebooting, I found it can not go back to desktop, and there is no prompt on the screen. the more panic thing is that even using ctrl+alt+f2 can not change it into command prompt.
to solve the problem, first I went to the recovery mode of debian. in there you have to input the root password. then I have the access to folders.
It is found that there is no wlan working at the moment. to figureout that I followed
http://www.ghacks.net/2009/04/14/connect-to-a-wireless-network-via-command-line/
but actually it doesn't work
so instead, I uninstalled the ATI driver, then it is able to boot into desktop. after update the new driver, it is able to work now.
this reminds me the case a month agao on scientific linx. there is also same problem. to fix it, one has to update the video driver. but my questions is: since debian and SL are all old versions of linux how can the drivers no compatible?

use smb (samba) mount on terminal

it was found that some of the file manager, like dolphin, is really slow in mounting on sshfs. it happens when I mount hdrive by
$ sshfs username@mango.eait.uq.edu.au:/home/users/username /home/chenming/Hdrive -o idmap=user
The best way is to find out how the file system is constructed. later on I knew that mango is not the file server, but it has the access to the file system. the real file server is smb://file.eait.uq.edu.au so we need to find out a way to mount smb server on terminal. here is the way
# mount -t cifs //file.eait.uq.edu.au/username /home/chenming/Hdrive -o username=username,password="yourpassword",domain=UQ,rw,nounix,iocharset=utf8,file_mode=0777,dir_mode=0777,gid=1000,uid=1000

the gid and uid in the behind is the same as the user you want to give read write permission.
it turns out to be much faster than I mount the system by sshfs.


SOLUTION:

First make sure that gvfs has been emerged with flag samba.
Second, make sure run the nautilus with dbus:

$ dbus-launch --exit-with-session --sh-syntax nautilus

You probably need to wait for one minutes until dbus gets ready.
Then go to connect to server, type

smb://file.eait.uq.edu.au/home/

or

smb://file.eait.uq.edu.au/software/

One should make sure after smb being typed, there is no notation like "this file server type is not recognized". If not, after entering the command, one should expect an window requiring username and password. make sure that domain is named as "UQ".

Now, one should be able to see the mounted folder from nautilus.

It is noted that one may not be able to directly access the remove folders from commandline. In fact, the location has been mounted in 

/run/user/{UID}/gvfs/

Work done!