Linux Tips & Tricks

I still like RedHat servers and Fedora, what can I say? It is like an old heartache that never really goes away. I used to install RedHat Linux on multiple boxes when it was really free, if you know what I mean. Fedora, naturally, was another story. Due to its experimental nature, it was kind of risky to set it up as a production server - too much headache if something goes wrong. But I know a lot of system administrators braver than me, who, actually, run Fedora versions as production servers.

Well, I don’t know about you, guys, but I can’t afford to pay thousands of bucks for RedHat server “support”. That is why, it was such  a relieve for me when CentOS showed up and  saved the day. For those who does not know (is there anyone, I wonder?),  CentOS is a clone of RedHat server and a damn good one.  Its name has nothing to do with cents. This is just an abbreviation for Community Enterprise Operating System.

When I downloaded for free and installed my first CentOS I could not believe my eyes - it turned out as stable as its expensive daddy RedHat.  And if fact, that is what this company aims to - to be 100% binary compatible, as RedHat. You know that when a company has great product, in most cases this simple fact guarantees company’s longevity. I don’t know, if the guys there make any decent money. All I can say is that CentOS recently turned its 4th year of existence - this proves something, doesn’t it?

CentOS is pretty consistent, they produce a new version as soon as RedHat comes out with a new server.  So, I would say, it is, basically, the same as RedHat, but better, because it is free. And a number of web hosting companies are using CentOS for the same reasons.  And my web analytics company is no exception. So, why don’t you go and try CentOS too?

I think many pros would agree that Putty is still the best free ssh client to use on Windows machines. It has  always been loyal to me and, practically, never let me down for the last ten years or so, since I’ve been working for my web analytics company. Putty comes in various versions: you can download just Putty for all your telnet and ssh needs, or you can also add to it PuttyTel, PSFTP and other clients. Putty.exe is just one file, after download you can move it right on your desktop and open directly from there.

I noticed not so long ago, though, that there were no recent updates for Putty. The last client 6.0 beta was produced for download on April 29, 2007. I really don’t know what happened, maybe developer just got tired of us or moved to some other venues. But the client is still working great. In fact, I just installed it on another new Windows XP box  and use it without any issues. Here is the link, so you can download your Putty client.

Everywhere you go now, you hear people say these mysterious words like Search Engine Marketing. Some folks are so lazy to pronounce all three words, so they abbreviate them just to Search Marketing. When guys talk about SEM, they make it sound like this is some sort of voodoo magic. They try to figure out search engines behavior and algorithms, guess why a bunch of pages appear or disappear from the search. OK, so maybe, partially, they are right, maybe SEM is partially some secret magic. Yet, anyway, what is the big deal about Search Engine Marketing?

I am not going to give some simpleton examples, like they do in recent books, when they compare SEM to a car or a tree. No, folks, you are much smarter than that. Basically, Search Engine Marketing is about the ways to increase traffic to the website from the search engines. And then, simultaneously or consecutively, convert part of the visitors into buyers. This is, practically, all about it.

OK, smartie, you may say, we knew that before. But what about the methods to achieve this traffic increase? Well, as far as I know, there are three main SEM methods. Search Engine Optimization (or SEO for lazy folks), Pay Per Click Bids Management (you can shorten the first three words to PPC, although this sounds nasty), and Web Analytics (you may or may not call it WA).

Search Engine Optimization is about changing the code of your pages and the structure of your site in such a way that when an SE spiders, and other robots read the site, they can understand that the pages have valuable content related to your keywords, and then rank them high. And, sorry, spiders can read only regular HTML. They don’t understand anything fancier HTML, like JavaScript or Flash. SEO also tells about ways to increase your link popularity - the number of links from other high-ranked pages to your site. Most search engines consider your link popularity a vital ranking factor.

Pay Per Click Bids Management is all about the money you spend trying to maintain your search engine visibility in the sponsored listings, by controlling your bids. Usually you try to detect the best converting keywords and keyword groups, in order to increase bids on them; as well as decrease or take off bids on keywords that don’t break even. Dont’ forget to leverage your paid and organic listings, so you may spend less on paid advertising campaigns when you get enough traffic from natural results. You should, probably, also invest in paid advertising when an algorithm changes or strong competitors force you out from the top positions in the organic listings.

Web Analytics is all about Internet analysis. You need to be able to analyze the information you get from your web site visitors. Any kind of details may be extremely important. Their behavior on your site, navigation clicks that they use, the ways they found your site, the efficiency of referrers and advertising, conversion rates, and, naturally, e-commerce information.

I will continue publishing blog entries about SEM, because today, it is on the rise and part of sysadmin requirements is to learn how to quickly conduct the web site optimization, and web site analytics.

Like its big brother Sendmail, Postfix is an open source mail transfer agent (MTA) for routing and delivery of e-mail. It is fast and easy to administer. You can even use for administration a nice web inteface of Webmin.  Postfix was originally written by Wietse Venema and released somewhere in 1999.  The majority of our web analytics company MTAs are Sendmail servers, but we also use a couple of Postfix machines for handling humongous amounts of statistical reports that our Web analysts send back and forth.

Since 1999, Postfix definitely matured.  Right now, I see two major strong points for using this MTA.  Fist of all, it has amazing resilience against buffer overflows. Sendmail is more vulnerable, I must say (although, I love Sendmail).

Second major plus is the way Postfix is handling huge amounts of e-mail.  This baby just does not go down, no matter what!  Another one is its handling of large amounts of e-mail. Its creator Wietse Venema (also a creator of tcp wrappers)  built Postfix  as a cooperating network of different daemons. Each daemon fulfills a single task using minimum privileges.  Even if a daemon is compromised, the impact remains limited to that daemon. It cannot spread throughout your entire system. There is only one process with root privileges, and a few that actually write to disk or invoke external programs. Besides, most Postfix daemons can be easily chrooted.

There are several nice books on Postfix that you can buy at Amazon.com.  One of them is really good. Yet, here is what I say. Save yourself some money. I suggest you go straight to Postfix online documentation and get everything that is written in the books for free. I am not kidding, it is true.  Click on the link above and check it out yourself. If you think, that this is too complicated, choose from here Postfix basic configuration online tutorial.

Big shots and other capitalists don’t feel that a poor sysadmin has enough responsibilities in his life. In addition to managing systems, servers, open source software, cleaning spam from e-mails, they also want a sysadmin to manage, program, design their web sites. The average sysadmin Joe works his ass off, while still being underpaid. But this is life, what can I say?

Speaking of Web, I always enjoyed reading Jacob Nielsen articles about web usability. I can’t say that I agree with everything he says. Yet, I must admit, that sometimes obvious things escape our attention and crawl into our web pages. Then, these flaws get piled up, and one day, we have to drop everything and sacrifice our precious time to adjust the sites accordingly. Trust me, in our web analytics company, we encounter that kind of situation from time to time. If only we had listened to old Jacob (sigh!)…

So, I highly value and recommend to go through useit.com that Jacob Nielsen still supports for free, although he could charge big bucks for it. You will learn what is so important today in the terms of web usability, and, hopefully, you will pass this learning curve to others.

There is a lot of books written about MySQL, some of them are very deep and profound and explore endless possibilities of this true “people” database server. But very often this is not for a beginner, who just enters the world of databases, needs. He needs to read a little and to build upon it fast, especially if his manager is very demanding.

Well, dear friends, save your money and go directly to the source. It should help you to start with MySQL in a couple of days (if not the same day).  There is a nice tutorial in MySQL reference manual written by developers of this database server.

Honestly, my dream is to find a great book on Apache server. From time to time I still keep this dream alive by religiously buying newly published books on Apache. But after reading half of the new book, I realize, that I am not getting any new “inside” information that will put AFG Solutions ahead of its competitors.

So, here is my conclusion: You may find anything about Apache Web server, its new features, configuration, etc on Apache’s own web site. I think, we are just getting too lazy to read stuff off Internet, plus the above mentioned reasons that I was talking about. And I also, honestly, think, that authors got our attitude and make a lot of money on us by just rephrasing the same information taken from Apache Web site. Apache.org is a truly great site, maybe a little bit chaotic and slightly disorganized. But that is where you need to turn to in your times of trouble.

We all had problems with Linux and sometimes had to spend hours searching for solutions, googling and surfing message boards. Would not it be nice if the whole troubleshooting guide will be in one place?

There are many sites that try to create that kind of all-encompassing tutorial for troubleshooting with different level of success.  I can recommend one of them that stands aside from the others. This Wiki deals with software and debugging mostly, but people of various Linux/Unix skills might fine them intriguing. So, read on!

In my Web Analytics company, I occasionally had problems with Linux servers, because they tended to cache a lot of stuff. Especially, this problem occured, when I was manually copied a lot of files or was doing a tar backups for one of our clients. Well, there is an easy  solutions for this issue now

Kernels 2.6.16 and newer provide a mechanism to have the kernel drop the page cache and/or inode and dentry caches on command, which can help free up a lot of memory. Now you can throw away that script that allocated a ton of memory just to get rid of the cache…

To use /proc/sys/vm/drop_caches, just echo a number to it.

To free pagecache:

# echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:

# echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:

echo 3 > /proc/sys/vm/drop_caches

As this is a non-destructive operation and dirty objects are not freeable, the user should run “sync” command first!

I can’t express how happy I was when I built my first Samba server. I used my old box that was no good for running Windows file-and-print server, did not have enough memory or storage for that “perfect” Microsoft configuration.

This was a while ago. Those who did not have their own Samba, had to cough up a chunk of money for Windows “solutions”.

Anyways, when I saw that server icon from my Windows workstation, I was walking on heaven… After a while, I thought and created networking environment for all my printers. They started running off my mentioned above Samba server, unclogging my not -so-fast home LAN.

When hard drives became much bigger and printers more sophisticated, having Samba servers made even more sense. Anything, just anything that was not worth while keeping on our workstations went to Samba servers. Each person had his own share, where he could work and in the end of the day save all his stuff. Windows workstations were running faster and no information was getting lost or slipping through the cracks.

There is an unthinkable number of configurations that you could for your home LAN, office LAN, medium-size or big corporation. The settings are are easy, as a rule, if you know what you are doing. If you don’t, well, go to the main Samba site, click on Documentation link and knock yourself out. I swear, you won’t regret it.