Posted by The TechMentor in CentOS, Configuration, Linux, Ubuntu
on Dec 2nd, 2012
Sometimes you have servers hanging out in the public internet in ways that you have little control over the network and hardware firewalls. Setting up a hosted server, such as a Virtual Private Server (VPS) or “node” in the cloud can be scary. Fortunately software firewalls, such as iptables, can add a little to piece of mind. But, in these days of automated attacks, it is still not enough. Usually the primary means of access to these servers is SSH. There are a couple really simple things can be done to make SSH more secure. I recently setup a new node on Linode. In the first hour there...
Posted by The TechMentor in CentOS, Configuration, Linux
on Dec 2nd, 2012
I recently setup a CentOS 6.3 server on Linode.com. One of the first things I wanted to do was lock it down with iptables. Unfortunately iptables was not starting cleanly. Specifically, It was failing here: Iptables Error – Setting Chains To Policy ACCEPT: Security Raw Nat Mangle Filter [FAILED] It turns out that was happening due to the paravirt kernel having a “security” chain compiled into it, and the default “iptables” init script included with CentOS does not know how to handle it. After a bit of searching I found a patch for the init script, posted by one of the...
Posted by The TechMentor in Configuration, Linux, Ubuntu
on Nov 30th, 2012
Once Nagios was setup on the little Minecraft server, it needed to be configured to send email. These days I prefer to relay through one of my Google Apps accounts, so I set forth to setup GMail as a relay using Postfix, which was already installed, but not really doing anything. Using Postfix always seems to be an issue with me, since I have more experience with Sendmail. However, having done this recently on a few Macs, I figured what the heck. Here’s a quick overview of the process: Install Postfix (if not already installed). Configure Postfix (if no main.cf exists). Use: sudo...
Posted by The TechMentor in Email, System Configuration, Ubuntu
on Oct 30th, 2012
Setting up GMail as a relay in Postfix always seems to be an issue with me. Here’s a quick overview of the process: Install Postfix (if not already installed) Configure Postfix (if no main.cf exists). Use: sudo dpkg-reconfigure postfix Generate CSR, in /etc/postfix/certs /usr/lib/ssl/misc/CA.pl -newca openssl genrsa -out itchy.key 1024 openssl req -new -key itchy.key -out itchy.csr openssl ca -out itchy.pem -infiles itchy.csr Edit main.cf relayhost = [smtp.gmail.com]:587 #auth smtp_sasl_auth_enable=yes smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd #tls smtp_use_tls = yes...
