Linux:GUI troubleshooting

Linux server's can be accessed through GUI(Graphical User Interface) or CLI(Command Line Interface).

Some times User will face some issues when accessing GUI such as

• Blurred screen.
• System crashes when users try to access GUI.
• Only particular user will face an issue not able to access GUI.
• Resolution problems.

In order to resolve this issues we have to pin point the problem, check weather its a problem with the single user or all the users in the server not able to access the GUI

ISSUE1: If it is for a single user this GUI related problems will occur due to some space issue
So check these following things

1. Check weather his disk quota is exceeded or not(when ever GUI is started in Linux/Nix it require some temporary space which is used to store some temp files for the purpose of GUI running), so if there is no free space left for the user GUI will not start for that particular user.
2. Remove temporary files which are not in use for that particular user.

ISSUE2: If the GUI is not working for all the users then there is some configuration issues in xorg.conf file.

The best and simple way to resolve this issue is just take a backup of the existing file and regenerate the new config file

#mv /etc/X11/xorg.conf /etc/X11/xorg.conf.old

Regenerating new GUI configuration file

#system-config-display

this command will regenerate fresh GUI and it will ask you for new resolution too, so set the new resolution to your requirement.

Like the post? Please Subscribe to free RSS feed to get updates

DNS Troubleshooting in Linux

Some basic DNS troubleshooting in Linux.

1. First collect the information which has created the problem by doing some investigation(such as logs, debug messages etc) .
   
2. Prepare your tools which is required for your troubleshooting.
3. Troubleshooting is nothing but considering so many issues that may cause the problem and working one by one to pin point the actual culprit which created the issue.
   
4. once issue is pin-pointed you have to work on that issue with the tools/commands/logs all other resources and have to resolve it.

Coming to troubleshooting DNS aka named services, here are the steps how we can resolve the DNS related issue:

I will take one scenario "suppose my client is unable to resolve host-names to IP address"

Step1:Check the DNS server is configured on Client end or not

check in below file if name server is configured to proper DNS server or not
#vi /etc/resolv.conf

If the client is configured with proper DNS server follow to next step

Stpe2:Ping to DNS server ip address

#ping serveripadd

If pinging is happening proceed with the next step other wise click here to do network troubleshooting.

Step3:So pinging is happening... then there is a communication path between Server-client, so we have to check weather DNS server is running or not. Here nmap can be used to check what ports opened on server.

#nmap serveripadd

Example:

#nmap 125.22.73.23

this command will give you output what are the services running/ports opened on remote server, if DNS server is running and working fine means you can see DNS port(53) in the list of opened ports. If suppose server is not running/port blocked you can click here to troubleshoot in this way.

Step4:Now checking DNS server issue in deep

• Checking under whom the DNS server is register and its properties .
  

#whois example.com

• Checking what server is used to resolve and some basic info.

#nslookup www.example.com

• Checking who is resolving and what is resolving in details about DNS server.

#dig www.example.com

Like the post? Please Subscribe to free RSS feed to get updates

Disabling SELinux

Some basics of SELinux :
How to disable SElinux?
SElinux is a security feature which was shipped with RHEL5, it is much secure than any other security priviously such as PAM and Initd




Here we are going to see some basics of SElinux.

Step1:Seeing whether SELinux is enabled or not ?

#getenforce

Step2:To see SELinux status in elaborated way you can use sestatus
#sestatus
SElinux status : enabled
SELinux mount : /selinux
Current mode : enforcing
Mode from config file : enforcing
Policy version : 21
Policy from config file : targeted

From the above output we can see that SElinux is enabled and its in enforced mode.
and to see detailed status you can use -b option, this will give which service are SElinux enabled and which services are disabled.

setenforce
/etc/grub.conf and /etc/selinux/config

Step3:disabling SElinux
We can do it in two ways
1)Perminant way : edit /etc/selinux/config

change the status from enable to disable and selinux type from strict to targeted, after changes are made we have to restart, if the server's are in production and don't want to restart the server follow the temporary way of disabling it.

2)Temporary way : echo 0 > /selinux/enforceFor your info if you want to enable it again, try below commandecho 1 > /selinux/enforce.
Selinux is a vast subject and can not deal in one post, see for my other posts regarding Selinux.

Like the post? Please Subscribe to free RSS feed to get updates