I have been using Cacti, a RRDTool-based graphing solution, to monitor my servers/VPS over the last year or two (and before that, with MRTG). My needs are simple — I just need graphing of several server metrics and Cacti fits the bill perfectly when the data is well supplied. Cacti is installed on one of my servers, and it will pull stats from my other servers all around the globe at 5 minutes interval.

Data collection from the actual servers is another story. Usually I need

• Number of bytes transmitted and received on all network interfaces except local.
• Current load average over 1 minute, 5 minutes and 15 minutes.
• Current memory usage.

Two months ago I had written an article on tuning GCC parameters for compilation under low-memory VPS, by limiting the maximum memory it can use, which is often useful on user-bean-counter based VPS’s (OpenVZ and non-SLM Virtuozzo). It worked in most cases on my 256Mb VPS at VPSLink, but in some circumstances the packages just won’t compile.

If you have an email address for a while, you’ll know that “spams” are almost inevitable. Once the email address has been used, spams will find their way there sooner or later. Combating email spams has also become one of the most researched topics these days.

Greylisting is a relatively new method to use against spams, and its principle is very different from traditional content filtering/content classifying strategy. The differences make it very effective in stopping spams currently, utilising relatively little CPU time and has small memory footage. It by no means is a replacement for fiter/classifier based spam protections, but can be easily deployed as first level of defense to reduce the CPU/memory demand of your spam filters.

This article was written after successfully implementing greylisting on Postfix using Gld, on a memory-restrained VPS running Gentoo Linux. Hopefully it will be useful to those who are thinking of implementing a similar solution.

There is an interesting forum post explaining how you can get Gentoo to emerge essential packages on VPSlink’s basic VPS with only 64Mb of memory! I originally thought it would be impossible, but by mangling GCC’s garbage collection parameters it indeed can be done.

In this blog post I will be looking at cutting down the memory used by the Secure Shell daemon running on your VPS, by replacing it with a lite-version that does 90% of what OpenSSH can do — Dropbear.