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Checking whether IPv6 is Enabled

Open up a terminal and type:

ip a | grep inet6

If it there is any output, which shows something like:

inet6 ::1/128 scope host

then IPv6 is enabled. If there’s no output, then IPv6 is disabled.
Disabling IPv6
Instructions for Ubuntu 8.04 LTS (Hardy Heron)
Ubuntu 8.04 LTS Server Edition (to disable before installation)

This is similar to adding the “noipv6” boot option in Red Hat / Fedora / CentOS during installation. The file “/etc/modprobe.d/blacklist.local” with content shown below will be created:

# Local module settings
# Created by the Debian installer

blacklist ipv6

1.

Boot the Ubuntu 8.04 LTS Server Edition Installation CD (of course!)
2.

Select your language
3.

Highlight “Install Ubuntu Server” (DO NOT press “Enter”)
4.

Press the function key “F6”
5.

Add “ipv6.blacklist=yes” to the kernel parameters (The line should read “… — ipv6.blacklist=yes” afterwards)
6.

Press the “Enter” key to continue with the installation as usual

Ubuntu 8.04 LTS Desktop Edition (to disable before installation)

1.

No method as far as I know. Please follow the instructions below.

Ubuntu 8.04 LTS (to disable after installation, by blacklisting the ipv6 module)

Copied from the manpage of modprobe.conf(5):

blacklist modulename

Modules can contain their own aliases: usually these are aliases describing the devices they support, such as “pci:123…”. These “internal” aliases can be overridden by normal “alias” keywords, but there are cases where two or more modules both support the same devices, or a module invalidly claims to support a device: the blacklist keyword indicates that all of that particular module’s internal aliases are to be ignored.

On Debian and Ubuntu systems this keyword applies to user-defined aliases as well.

NOTE: Blacklisting a module does NOT prevent a module from being loaded if it is needed by a system service, regardless of the fact that it has been blacklisted. Besides, it does NOT prevent the module from being modprobe’d by root. You may want to disable IPv6 by aliasing net-pf-10 to off. Please refer to the section below for instructions. You may have read tutorials that teach you to append a line to “/etc/modprobe.d/blacklist”, but in fact it is NOT RECOMMENDED to do so. It is more appropriate to write manual configurations to a separated file (i.e. local configuration file) whenever possible, so that the configuration files distributed by the system keep their original content. The following instructions create the file “/etc/modprobe.d/blacklist.local” by mimicking what is done by the Ubuntu installer (i.e. Debian installer) when “ipv6.blacklist=yes” is added to the kernel parameters during installation:

1.

Open up a terminal and type:

sudo sh -c ‘echo blacklist ipv6 >> /etc/modprobe.d/blacklist.local’

The above command appends a line to the local blacklist configuration. The file will be created if it does not exist.
2.

To restart your computer, type:

sudo reboot

Ubuntu 8.04 LTS (to disable after installation, by aliasing net-pf-10 to off)

Copied from the manpage of modprobe.conf(5):

alias wildcard modulename

This allows you to give alternate names for a module. For example: “alias my-mod really_long_modulename” means you can use “modprobe my-mod” instead of “modprobe really_long_modulename”. You can also use shell-style wildcards, so “alias my-mod* really_long_modulename” means that “modprobe my-mod-something” has the same effect. You can’t have aliases to other aliases (that way lies madness), but aliases can have options, which will be added to any other options. Note that modules can also contain their own aliases, which you can see using modinfo. These aliases are used as a last resort (ie. if there is no real module, install, remove, or alias command in the configuration).

This is the official way to disable IPv6. The instructions below is equivalent to that documented in [WWW] Documentation for Ubuntu 8.04 LTS – 3. Wireless Networking – Troubleshooting:

1.

Open up a terminal and type (it is recommended to copy-and-paste it instead):

sudo sed -i -e ‘s/alias net-pf-10 ipv6/#&\nalias net-pf-10 off/’ /etc/modprobe.d/aliases

The above command comments the original line (alias net-pf-10 ipv6) and adding the effective line (alias net-pf-10 off). You may use your favorite editor to achieve the same result, if you find that using sed does not meet your taste 🙂 .
2.

To restart your computer, type:

sudo reboot

Ubuntu 8.04 LTS (to disable after installation, by installing ipv6 as a no-op)

Copied from the manpage of modprobe.conf(5):

install modulename command…

This is the most powerful primitive in modprobe.conf: it tells modprobe to run your command instead of inserting the module in the kernel as normal. The command can be any shell command: this allows you to do any kind of complex processing you might wish. For example, if the module “fred” worked better with the module “barney” already installed (but it didn’t depend on it, so modprobe won’t automatically load it), you could say “install fred /sbin/modprobe barney; /sbin/modprobe –ignore-install fred”, which would do what you wanted. Note the –ignore-install, which stops the second modprobe from re-running the same install command. See also remove below.

You can also use install to make up modules which don’t otherwise exist. For example: “install probe-ethernet /sbin/modprobe e100 || /sbin/modprobe eepro100”, which will try first the e100 driver, then the eepro100 driver, when you do “modprobe probe-ethernet”.

If you use the string “$CMDLINE_OPTS” in the command, it will be replaced by any options specified on the modprobe command line. This can be useful because users expect “modprobe fred opt=1” to pass the “opt=1” arg to the module, even if there’s an install command in the configuration file. So our above example becomes “install fred /sbin/modprobe barney; /sbin/modprobe –ignore-install fred $CMD-LINE_OPTS”

1.

Open up a terminal and type:

sudo sh -c ‘echo install ipv6 /bin/true >> /etc/modprobe.d/blacklist.local’

The above command appends a line to the local blacklist configuration. The file will be created if it does not exist.
2.

To restart your computer, type:

sudo reboot

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