Howtos / Articles

How To Disable IPv6 on Ubuntu

A default install of Ubuntu will enable IPv6 connectivity. If you don’t need IPv6, there is no need to have it enabled. Follow the steps below to disable IPv6 on a Ubuntu install. Check to see if you’re installation is currently set up for IPv6: $ cat /proc/sys/net/ipv6/conf/all/disable_ipv6 If the output is 0, IPv6 is enabled.
If the output is 1, IPv6 is already disabled. Edit the /etc/sysctl.conf file to set the kernel parameter to disable IPv6: $ sudo nano…

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Change the IPTables log file

An important aspect of any firewall are the log files. Iptables on Linux provides logging functionality, however by default, it will get outputted to the /var/log/messages log file. This can clutter things up, and make it hard to check the logs. If you want to change the file that IPTables logs to, you need to set up your iptables rules to output a log prefix. Rsyslog will then be configured to pick up this prefix, and output the information to…

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Backup your master boot record

The Linux DD command allows you to read and write directly to block devices. If you are playing around with boot loaders, dual booting, etc, its a good idea to take a copy of your master boot record just in case things go astray and you need to restore it. To backup the master boot record (MBR): $ sudo dd if=/dev/sda of=boot.bin bs=512 count=1 /dev/sda is the device of the hard drive you want to take the backup from. boot.bin…

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Run Postfix on multiple ports

The default port for SMTP is port 25, but there may be some scenarios where you may need Postfix to listen on another port as well (or instead of). For example, if you want to send emails via your own mail server, from your work computer, but the work network may be blocking all port 25 traffic out onto the internet from all PC’s but the mail server. You can get around this by setting up Postfix on another port…

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Limit Postfix to listen on specific IP addresses

On a default install of Postfix, it will listen on all interfaces/IP addresses on your machine. Sometimes this is not what you want. For example, the computer may be connected directly to the internet on one network interface, and connected to a lan on another interface, however you may not want to allow access to the SMTP server from the internet, and only use it for internal mail. You can do this by specifying only the internal address to listen…

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