Basically Tech - technical

Debian lenny MailScanner woes

nospam@example.com (Rob Newcater) — Fri, 03 Apr 2009 13:58:28 +0100

I ran a system upgrade (from etch to lenny) on one of my Debian servers today. There seem to be lots of people who have their own ideas about how to go about this, which is fair enough, there's more than one way to climb the mountain. In fact I deviated (very) slightly from the steps kindly provided in the official upgrade instructions.

I double-checked the official issues to be aware of for lenny. Nothing about MailScanner!

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Linux tips every geek should know

nospam@example.com (Rob Newcater) — Mon, 02 Mar 2009 11:25:01 +0000

This is a great collection of random Linux tips (57 in all). They were originally published in Linux Format magazine. The various tips are categorised into three levels of difficulty, easy, intermediate, and expert. Well worth a read.

sed and iostat

nospam@example.com (Rob Newcater) — Sat, 22 Nov 2008 03:23:21 +0000

I'm sure many Solaris admins will have come across this problem before. You have a SAN-attached host with dozens, maybe even hundreds of visible LUNs. Each LUN has a highly improbable and unwieldy name, as some of these SAN-attached devices do, and you need the iostat data for that LUN.

grep is no help, because you also want the four lines of data beneath the 'disk' name.

Well, you could just run iostat and painstakingly trawl through hundreds of lines of data, searching for the information you need. Or you could use the goodness of sed to find your LUN, and the four lines of data beneath it ...

$ iostat -En | sed -n '/c4t60060480000290101035533030433430d0/{p;n;p;n;p;n;p;n;p;}'

c4t60060480000290101035533030433430d0 Soft Errors: 0 Hard Errors: 1223 Transport Errors: 1170
Vendor: EMC      Product: SYMMETRIX        Revision: 5771 Serial No:
Size: 54.41GB <54408314880 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 75 Recoverable: 0
Illegal Request: 0 Predictive Failure Analysis: 0

And that is a genuine LUN id!

Colour-coded battery charge level and status in your bash prompt

nospam@example.com (Rob Newcater) — Thu, 11 Sep 2008 12:23:57 +0100

I recently purchased a laptop, and having installed a proper OS, I found myself a little disappointed with the default battery meter provided by GNOME. Unless you mouse over the icon on the panel, it doesn't display exactly what charge level it is at. I am aware of the other options such as conky, gkrellm, screenlets, etc, but being the lazy sort, I consider it a long way to move your eyes! Since I'm the type who always has several terminals open, I thought it would be handy to display the charge level and status of the laptop battery in my shell prompt.

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find is an amazing tool

nospam@example.com (Rob Newcater) — Fri, 11 Jul 2008 00:02:36 +0100

I found a new article about the remarkable command-line interface utility 'find' today. It's a good article, but the best I've found so far is Daniel Miessler's excellent tutorial on the subject, which also incorporates some xargs goodness, something which the former sadly neglects.

Three awk resources (and one old sed)

nospam@example.com (Rob Newcater) — Wed, 14 May 2008 21:34:08 +0100

I use awk (or rather gawk and nawk) a lot, and I was intrigued to find two resources on the internet very recently. This sort of information used to be hard to come by, so it was good to find it.

The first (and IMO the best) resource I found was an awk tutorial called Getting started with awk.

The second was an Awk, Nawk and Gawk cheat sheet.

Add to that my old favourite Handy one-liners for awk, which seems to have taken it's inspiration from the venerable and much-queried Handy one-liners for sed, and you have the four resources hinted at in the title. I hope it proves useful.

The many uses of gcal

nospam@example.com (Rob Newcater) — Fri, 19 Oct 2007 11:59:00 +0100

gcal is a remarkable console-based program.

It can be used to print calendar information, much like cal, but with much more flexibility.
It can display holiday information for over 300 different countries and states.
It can display astronomical information such as sunrise, sunset, the current phase of the moon and much more.
It can also be used as a diary or personal reminder.
It can print the current date and time. (No, really! )
It can be used to display the start and stop of daylight saving.

I'll be providing examples of how to use gcal in all these ways. Bear in mind that this article just scratches the surface with regard to what gcal can actually be used for. You are limited by your imagination!

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Solaris: NIS installation and configuration

nospam@example.com (Rob Newcater) — Wed, 05 Sep 2007 14:26:09 +0100

(This article has been updated from the original, which focused on Solaris 8 only, to include Solaris 10-specific entries. Where the commands or entries for Solaris 8 and Solaris 10 differ, they are written down in purple for Solaris 8 and green for Solaris 10. In addition, I have added an extra note about changing the NIS Makefile in the event that you're not going to use group passwords.)

This is a step-by-step account of the method I used to install and configure a NIS master and slaves on servers running Solaris 8 (and more recently, Solaris 10). The steps detailed for Solaris 8 should work fine on earlier versions of Solaris, but as I have not explicitly tested other versions (except as clients) you may encounter issues. The clients used with this setup ranged from Solaris 7 to Solaris 10. The installation was in a medium-sized Solaris-only farm (100+ hosts).

Configuring NIS on Solaris is not quite as straightforward as it is on other OSes (such as some Linux distros). This didn't really surprise me, even though NIS is Sun's product. What this does allow is a more tailored end product.

There are three points I'd like to emphasise concerning this article:

This article is not an definitive how-to; there is more than one way to implement NIS. This way works, it's relatively straightforward, and is more secure than a default NIS installation.
This article is not an endorsement of NIS over other naming systems. My recommendation to the client was to use LDAP, but NIS had been used before, they were more or less happy with it *, and it did what they wanted it to. Having said that NIS is still used on many sites, it's versatile, it's easy to set up and maintain, and it can be made more secure without too much extra effort.
This article describes the set up of NIS only. Administration is another matter altogether.

(* The client's existing NIS setup was very old and exhibited quirky behaviour on some rare occasions. In addition, it had allowed encoded password values to be seen when running ypcat passwd. This was not acceptable.)

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Microsoft Fracturing the Open-Source Community?

nospam@example.com (Rob Newcater) — Tue, 07 Aug 2007 12:20:34 +0100

Mark Shuttleworth, the CEO of Canonical, the company behind Ubuntu Linux, thinks Microsoft has managed to fracture the Open-Source Community. He also suggests that what Microsoft is doing amounts to extortion:

"To say, as [Microsoft CEO Steve] Ballmer did, that there is undisclosed balance sheet liability, that's just extortion and we should refuse to get drawn into that game. On the other side, if Microsoft is concerned about its intellectual property, there is no one in the free software community that wants to violate anyone's IP. Disclose the patents and we'll fix the code. Alternatively, move on."

He's also noted that those companies which did make deals with Microsoft have made short-term gains, but will lose out in the long run.

"I don't think this will end well for the companies that slipped up and went down that road," Shuttleworth said. "Ultimately, it is the spirit of open source that really motivates your best developers. Developers have been abandoning Novell ever since they did the deal with Microsoft, and they have gone to Oracle and Google among others. That's unfortunate for Novell, but was a fairly predictable consequence of their decision and it ultimately portrays a lack of understanding about what it is that really empowers free software."

Linux OCR software review

nospam@example.com (Rob Newcater) — Thu, 24 May 2007 14:38:26 +0100

There is a very interesting and useful review of Optical Character Recognition software over at the groundstate.ca website. The quality of the packages tested varies, and the author recognises the usefulness of software having command-line capabilities (for running batches of conversions, for instance). Along with accuracy, ease of use is also tested, with many usage and build examples demonstrated. Well worth a read if you are interested in using OCR software on Linux.

Regular expressions

nospam@example.com (Rob Newcater) — Fri, 04 May 2007 20:39:16 +0100

Part nine of the IBM DeveloperWorks series Speaking UNIX focuses on regular expressions. This is a huge field, and as usual, there are some great tips here. Well worth a read.

Using a USB external hard disk for backups with Linux

nospam@example.com (Rob Newcater) — Mon, 23 Apr 2007 10:18:36 +0100

In this article, I show how I set up a recently purchased USB external hard disk drive as a backup drive for my Linux desktop PC. I'll delete the default FAT32 partition, create a new partition, make a reiserfs filesystem, and show how to use rsync to backup your important data.

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Shell stuff: job control and screen

nospam@example.com (Rob Newcater) — Mon, 26 Mar 2007 11:23:56 +0100

A look at using shell job control, plus a quick overview of what I consider to be the best alternative to job control, GNU screen.

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Solaris 8: NIS installation and configuration

nospam@example.com (Rob Newcater) — Mon, 15 Jan 2007 14:38:02 +0000

(This article has been redrafted to include Solaris 10-specific commands and entries, as well as retaining the original Solaris 8 commands. In addition a couple of typos have been fixed and an extra note about changing the NIS Makefile has been added. This original article has not been altered, so follow the link above if you want to see the redrafted article.)

This is a step-by-step account of the method I used recently to install and configure a NIS master and slaves on servers running Solaris 8. The steps detailed should work fine on other versions of Solaris, but as I have not explicitly tested other versions (except as clients) you may encounter issues. The clients used with this setup ranged from Solaris 7 to Solaris 10. The installation was in a medium-sized Solaris-only farm (100+ hosts).

There are three points I'd like to emphasise concerning this article:

This article is not an definitive how-to; there is more than one way to implement NIS. This way works, it's relatively straightforward, and is more secure than a default NIS installation.
This article is not an endorsement of NIS over other naming systems. My recommendation to the client was to use LDAP, but NIS had been used before, they were more or less happy with it *, and it did what they wanted it to. Having said that NIS is still used on many sites, it's versatile, it's easy to set up and maintain, and it can be made more secure without too much extra effort.
This article describes the set up of NIS only. Administration is another matter altogether.

Continue reading "Solaris 8: NIS installation and configuration"

Learn 10 good UNIX usage habits

nospam@example.com (Rob Newcater) — Sat, 16 Dec 2006 12:26:58 +0000

An article which shows 10 UNIX bad habits and teaches 10 good UNIX usage habits. This is all command-line stuff, and I found a couple of these to be things which I do/did. The only problem is trying to stop those bad habits which you've been doing for years ...