How to disable IPv6 in Fedora 17 ?

Problem:

How to disable IPv6 in Fedora 17 or in future versions of Red Hat Enterprise Linux ?

Environment:

Fedora 17
Future versions of Red Hat Enterprise Linux based on Fedora 17 and higher

Resolution

Set the following sysctl parameter

net.ipv6.conf.all.disable_ipv6=1 

With Fedora 17 kernel, ipv6 support is included in the kernel and is no more a module

How to add crashkernel parameter in grub2

Problem:

How to add crashkernel parameter in grub2 ?

Environment
Fedora 17
Furture versions of Red Hat Enterprise Linux based on Fedora 17 and higher

Resolution

Edit /etc/sysconfig/grub and append crashkernel=128M at the end of the line

GRUB_CMDLINE_LINUX="rd.md=0 rd.dm=0  KEYTABLE=us SYSFONT=True rd.lvm.lv=vg_prod231-187/lv_root rd.luks=0 rd.lvm.lv=vg_prod231-187/lv_swap LANG=en_US.UTF-8 rhgb quiet crashkernel=128M"

After making the change, update the configuration file for the GRUB 2 boot loader

grub2-mkconfig -o /boot/grub2/grub.cfg

You should not be editing grub.cfg by hand

Reboot the system

dishtv.in is not accessible via Squid

Problem

dishtv.in website is not accessible through Squid.

Following message is noticed in the browser


The following error was encountered:

• Read Error

The system returned:

    (104) Connection reset by peer

Environment

Squid 2.6.STABLE21-6
Squid 3.1.10-1

Resolution

Add the following to squid.conf  and restart squid service

via off
forwarded_for delete

Root Cause/Diagnostics

Site was accessible directly. Via squid, connection would reset abruptly

Only difference when accessed via squid and directly was the addition of

X-Forwarded-For and via headers in the HTTP request

X-Forwarded-for usually contains the IP address of the host that requested the website

Example: 

X-Forwarded-For: 192.168.0.1

VIA usually has information about the proxy server

Example

via: example.com 

Documentation:  forwarded_for and via

By disabling via off and setting forwarded_for delete, we disabling these headers in the HTTP request.

dishtv.in was accessible after making this change.

Disabling this header should not have any negative impact (AFAIK)