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T he following Exim mail servers error was encountered while sending out mails. The original error was experienced by Gravity Forms WordPress plugin. However, I was able to test it out by using command line to rule out the plugin.

someone@domain.com R=virtual_aliases: No Such User Here

The debug message I received via Gravity Forms is the following. This confirms the mail has been passed on from WordPress to the mail server.

2016-03-25 11:06:04.042599 - DEBUG --> GFCommon::send_email(): Result from wp_mail(): 1
2016-03-25 11:06:04.042748 - DEBUG --> GFCommon::send_email(): Mail was passed from WordPress to the mail server.
2016-03-25 11:06:04.153172 - DEBUG --> GFFormDisplay::handle_confirmation(): Sending confirmation.

Before I go any further, I would like to give some background information on domain.com, which the following aspects are hosted as below.

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Even though I am a big advocate on promoting IPv6, I have came across Debian’s APT / apt-get stuck with the following message. I believe it is due to an issue on the serve concerning the FQDN
http.debian.net and security.debian.org. The easy way to fix is to force APT to use IPv4 as opposed to IPv6.

0% [Connecting to http.debian.net (2a01:4f8:151:555d::42)] [Connecting to security.debian.org (2610:148:1f10:3::73)]
echo 'Acquire::ForceIPv4 "true";' | tee /etc/apt/apt.conf.d/99force-ipv4

Changing Linux Interface Numbering

T he following method is useful when you have cloned a Linux VM and end up with a interface other than eth0. This usually happen when you are cloning or creating a VM from template with interface name eth0 and the cloned copy will have eth1 and not eth0 as the interface name. According to VMware, this is by design and can only be fixed by the following method.

Start up the VM and open up the following file with your favourite text editor and find the interface you want to remove.

/etc/udev/rules.d/70-persistent-net.rules

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ifconfig: command not found under user mode

Running ifconfig will throw an error as ifconfig: command not found while running on usermode.

This can be fixed with the below Symbolic Link.

ln -s /sbin/ifconfig /usr/bin/ifconfig

SSH Automatic RSA Key login

The following method shows how to setup SSH Automatic RSA Key login with two simple steps.

Create RSA key on LOCAL Host without a passphrase.

ssh-keygen -t rsa

Copy the RSA key to the REMOTE Host, while making sure the directory .ssh exists within the user’s home directory.

cat .ssh/id_rsa.pub | ssh username@REMOTE.Host 'cat >> .ssh/authorized_keys'

If you want to have this feature from both direction, you need to do the above tasks from both servers.

How to change Squid cache administrator

The following on squid.conf will change the email address in error page which reflects…

“Your cache administrator is root”

Where root will be replaced with the email address below…

cache_mgr admin@domain.com

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