Showing posts from May, 2004

LPI certificate is not what I expected.

Last friday I got my LPIC Level 1.

They sent the certificate itself, an id card asserting "John Doe" is a certified LPIC Level 1 professional and an ad from

The certificate paper is cheap, too thin IMO. I thought Canada was the land of wood and paper :) Good quality paper shouldn't be so expensive there. And I paid 200 hundred dollars for that.

Also, it's bad propaganda since it sais I have a "[b]Level 1[b]" cert in big capitalized words. The unaware will underestimate my knowledges hehe.

Fedora Legacy is great

I just installed RH9, as required by the customer, and wondered if I would have problems with lack of official support and updates from Red Hat.

Thankfully, the Fedora Legacy project provides updates to RH9. It just takes a few commands, and it's all set.


Anti Spam Solution

A good anti-spam solution must have at least two approaches:

An RBL check, and a learning tool of some sort.

When deploying an RBL check solution, one must note that the lists should be picked carefuly, since they could block HAM either.

It is important to implement exceptions lists, either, in order to ignore some key entries in the lists (, for example).

About the learning tool, this will the topic for a future post.

How to interpret vmstat output

vmstat is a wonderful tool, whose output is a bit cryptic for the faint of the heart.

r: Processes actually running, waiting for some attention from the CPU
b: Uninterruptble sleeping processes (This I am yet to discover what does it mean)

swpd: Virtual memory usage (swap areas are listed in /proc/swaps)
free: Idle memory
buff: Memory used as buffers, like before/after IO operations, I guess
cache: Memory used as cache.

si: Memory swapped in from the disk
so: Memory swapped to the disk

bi: Blocks received from block device (like a hard disk)
bo: Blocks sent to a block device

in: The number of interrupts per second, including the clock.
cs: The number of context switches per second.

us: Time spent running non-kernel code. (user time, including nice time)
sy: Time spent running kernel code. (system time - network, IO interrupts, etc)
id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
wa: Time spent waiting …

The power of hdparm

This shows the power of a well set hard disk controller:

johnny:~# hdparm -tT /dev/hda

Timing buffer-cache reads: 128 MB in 0.58 seconds =220.69 MB/sec
Timing buffered disk reads: 64 MB in 8.89 seconds = 7.20 MB/sec

Timing buffer-cache reads: 128 MB in 0.60 seconds =212.66 MB/sec
Timing buffered disk reads: 64 MB in 1.57 seconds = 40.72 MB/sec

PS: The second test was made when the machine was under production. So the benchmark is underrated.