When setting up a workstation to connect to internet, you may come across a message
Determining IP information for eth0… failed
The above error message basically means that eth0 i.e your network interface card is not setup correctly.
Some of the commands that can come handy in troubleshooting where the error lies are listed below
$ dmesg | grep eth0
(displays information about the ethernet controller card, mac address etc.)
$ cat /etc/sysconfig/network(displays the network settings)
$ cat /etc/sysconfig/network-scripts/ifcfp-eth0
$ ifconfig eth0 down (to down the nic)
$ ifconfig eth0 up (to start the nic)
$ netstat -rn (display kernel routing IP table)
$ cat ifcfg-eth0 (eth0 configuration settings)
$ service network restart (restart the network settings)
$ ping -c4 google.ca(to check if the internet connection works)
$ traceroute google.ca (to check how the IP navigation path is set)
Refer Red Hat linux 5 configure network article for additional info
VMWare Player is a free software available from VMWare Inc. enabling the creation
of guest OS within an existing OS
Notes for a beginner …
* VMWare Player and VMWare Server are available for free
* A .vmdk file is the virtual hard drive for the guest OS
* A .nvram file stores the BIOS settings of the virtual machine
* A .vmx file stores the configuration settings for the virtual machine. All you
need is a text editor to edit the VMWare configuration settings.
* A .vmsd file stores information about VMWare snapshots.
Difference between which command and whereis command in Linux
For e.g. lets find where “samba” is located in a CentOS server
$ which samba
which command searches the list of programs listed down through the PATH settings
$ whereis samba
whereis command also searches for programs that are not present in the PATH setting
Apache errors and the approach to solve it
Premature end of script headers
500 Internal Server Error
The specified CGI application misbehaved by not returning a complete set of HTTP headers.
Some troubleshooting tips:
i) Check /var/log/apache2/error.log (in ubuntu, check the respective apache error log location for the messages)
ii) Check if the content type of the page is correctly set for the html content output.
print “Content-type: text/html\n\n”;
iii) Check if a valid permission has been given for the file to get executed. The file need permission 755 for it to be executed on the server.
iv) Check if the configuration path, inclusion path are set correctly in the referenced programs
Apache Permission Denied Error can be caused due to one of many configuration mistakes listed below
Check the apache configuration settings
i) The first is the reference to folder where cgi or perl files will reside and its execute permission settings
<ScriptAlias /cgi-bin/ /usr/local/cgi-bin/> <Directory "/usr/local/cgi-bin"> AllowOverride None Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch Order allow,deny Allow from all </Directory>
ii) The second is the proper add handlers that are set for the file execution
AddHandler cgi-script .cgi .pl <Files ~ "\.pl$"> Options +ExecCGI </Files> <Files ~ "\.cgi$"> Options +ExecCGI </Files>
Check the apache error log for any messages (/var/log/apache2/error.log).
Step 1: $ sudo apt-get install postfix
Postfix configuration screen throws you with the following options to choose from
i) No changes (no changes to configuration settings)
ii) Internet site (Mail sent and received using SMTP)
iii) Internet with smarthost (Mail sent to another machine called smarthost)
iV) Satellite system (All mail sent to another machine for delivery)
v) Local only (No network based mail system. Only applied to this local machine)
Session Fixation is method by which an intruder creates a session id which gets carried on when a user comes with that path and continues his/her activity on a website.
For e.g. an intruder may create a link to a site called samplesite.com as <a href=”http://samplesite.com/cart.php?PHPSESSID=Ax23mDud” />Sample Site<a>
When a user clicks on this link the session id gets carried on to the site ‘samplesite.com‘. The intruder waits for the user starts to perform a transaction on the site and will take over vital details by intruding user’s activity on samplesite.com.