The Linux Page

SSH authorized_keys features

Alexis Wilke — Tue, 09 Mar 2010 04:34:04 +0000

Pretty much every day I learn something... Today it will be the fact that you can enter variables in front of a key that will request the SSH deamon to verify a certain number of facts in regard to the connection being made.

For instance, it can automatically test that the IP address of the person connecting is a specific IP (if you have a static IP address, very practical!)

Details

Operating System:

Linux

Category:

Security

Mode:

Daemon

PostgreSQL and UNICODE

Alexis Wilke — Fri, 05 Mar 2010 04:18:28 +0000

Trying to create a database with UNICODE does not always work. There can be two problems:

The default database setup is ASCII (more or less considered ISO-8859-1)
The database cluster was compiled without UNICODE support

Now a day, the second case is quite unlikely and it means that you won't be able to use a UNICODE encoding unless you recompile the database system. Make sure you use the ./configure --multi-byte encoding for that purpose.

Details

Operating System:

Linux

Category:

Development

Category:

Storage

Mode:

Console

PHP CLI Segmentation Fault with pgsql

Alexis Wilke — Tue, 02 Mar 2010 08:43:22 +0000

Somehow, whenever I tried PHP CLI, it would crash because of PostgreSQL. (i.e. if I use the database in PHP through Apache, no problem, but the same script run via the command line, and it crashes on exit, no matter what I do with the resource handle.)

I was puzzled and did not really know what to do, but some people have found the solution. Now, what is really surprising is the fact that it has been around for ages and not yet fixed in the system.

The fact is, it does not matter too much as long as there is a work around, but you need to apply it yourself...

Details

Operating System:

Drupal

Category:

Development

Mode:

Console

My customer cannot edit pages?!

Alexis Wilke — Fri, 26 Feb 2010 20:35:34 +0000

I created a website and handed it to a customer... without realizing that the customer could not edit the pages of his site.

He reported the problem and I was rather surprised since I had not installed any module that would protect the editing of pages based on a role... what could it be? I checked the Drupal permissions a couple times... he had the right to edit all the nodes, his own and anyone else's, hmmm...

I looked at the code to try to figure it out, and there is a call to the filter module: filter_access($node->format).

Details

Operating System:

Drupal

Category:

Development

Mode:

Browser

Domain

Alexis Wilke — Wed, 24 Feb 2010 01:03:55 +0000

$1.00

Get 1 extra domain on our servers! 8-)

$1.00

Compressed CSS & Boost when developing

Alexis Wilke — Tue, 16 Feb 2010 23:39:13 +0000

On my sites, I'm using boost to allow much faster access time (close to instantaneous in comparison to hitting Drupal and all the database accesses...)

The result is great! But it generates some problems when you test a page. It does not get refreshed... Easy, you can clear the cache. Not advisable when your cache is around 10,000 files. A better way, is to go to that page and click on "Flush Page" (available in one of the blocks offered by boost.)

Details

Operating System:

Drupal

Category:

Development

Category:

Web Server

Mode:

Browser

Load Average, to know how busy your server is

Alexis Wilke — Sat, 06 Feb 2010 08:27:59 +0000

Whenever you run many applications on a server, such as many instances of your web server (i.e. Apache), you may want to know how much of the system is being used. This can be important to avoid overloading your system.

The load is computed by the kernel. The kernel knows how many processes are running and how much processing power your server has (i.e. how many processors.) With that information, it infers how many processes are being held back for a period of time. The default periods are 1, 5 and 15 minutes (I'm sure you can recompile your kernel with different timings!)

Details

Operating System:

Linux

Category:

Web Server

Mode:

Daemon

MS-Access Report not printing

Alexis Wilke — Wed, 03 Feb 2010 19:08:12 +0000

1) Reports, Print and Load() Event

Back to summary

I wrote many forms and in general everything works just fine.

In this case, I wanted to enter the data with a function so I could properly format several of the fields (especially the billing and shipping addresses.) That was done on the Load() event. That function working great when looking at the report from within MS-Access (on screen report). However, when directly sending the report to the printer, it was not working well at all.

Details

Operating System:

MS-Windows

Category:

Development

Mode:

GUI

Table owner in PostgreSQL

Alexis Wilke — Tue, 02 Feb 2010 06:10:34 +0000

System tables and how to edit them is just not defined in the SQL language, unfortunately. So different database systems have different solutions to handle their table declarations. PostgreSQL is no different.

In most cases, MySQL uses some special instruction to update system information. In PostgreSQL, you have internal tables that the administrator can access and tweak as required.

Details

Operating System:

Drupal

Operating System:

Linux

Category:

Development

Category:

Storage

Mode:

Console

Confirm subscription

Alexis Wilke — Mon, 01 Feb 2010 07:00:35 +0000

Please, click on Confirm below to start your subscription.

Unsubscribing

Alexis Wilke — Mon, 01 Feb 2010 06:26:00 +0000

Please, take a minute to let us know why you want to stop your subscription with us and select one of the following choices:

Draw circle

Alexis Wilke — Sun, 31 Jan 2010 04:02:51 +0000

void Image::DrawCircle(float x, float y, float radius)
{
  // TODO: add tests to prevent computing all the points for nothing
  //       (i.e.

Factorial

Alexis Wilke — Sun, 31 Jan 2010 03:44:20 +0000

// slow integer factorial function
int factorial(int n)
{
  int r = 1;
  while(n > 1) {
    r *= n;
    --n;
  }
  return r;
}

Creating a Trigger in Drupal

Alexis Wilke — Wed, 27 Jan 2010 11:15:16 +0000

I have been wondering, for a while, how the triggers where generated in Drupal. I know that one can catch a message by writing a hook function and you have hundreds of those available. However, how are the triggers working?!

The fact is that triggers require you to write a function. The Core Trigger module has a set of specialized functions for the Core modules and it is limited to that. In other words, you cannot expect new modules to simply define an array and get the triggers to work (I was really wondering how could that really work?!)

Details

Operating System:

Drupal

Category:

Development

Highlighting

Alexis Wilke — Sat, 09 Jan 2010 22:20:23 +0000

// cool highlighting!
$f = fopen(source, "rb");
while(!eof($f)) {
  $s = fgets($f);
  $h = parse($s);
  echo $h;
}

Clean URL not working on my Drupal site?!

Alexis Wilke — Thu, 07 Jan 2010 10:39:35 +0000

Today I finally solved a problem that was bothering me for a while. A Drupal site I installed for a friend of mine would not accept the Clean URL set. This is when the URL does not need to include the rather ugly ?u=<path>.

The more I was looking into it and the more it looked like the problem was coming from the Apache installation.

Details

Operating System:

Drupal

Category:

Development

Mode:

Browser

SeaMonkey 2.0

Alexis Wilke — Sun, 27 Dec 2009 23:27:06 +0000

I guess I liked Netscape just way too much... I used Mozilla after Netscape went down and bust, then I continued with SeaMonkey 1.x and now I just finished installing SeaMonkey 2.0.

There are features in this system that are just better than in FireFox. However, SeaMonkey 2.0 is a re-sync. with FireFox 3.x. In other words, this is very similar to FireFox, with the correct display features of the HTML code. But it keeps the menu, preferences and look in general of SeaMonkey. (although the fonts have changed... I'll have to get used to those!?)

Details

Operating System:

Linux

Category:

Desktop

Category:

Storage

Mode:

Browser

Ada Variables

Alexis Wilke — Sat, 05 Dec 2009 20:56:29 +0000

Ada variables are complex objects. When developing a compiler, you must definitively take that in account. You have several sides to your variables: one you need to be able to handle dynamic variables since the compiler will have to be capable of doing all the operations on all the constant variables just as if you were executing your program and it has to handle all the tests necessary to ensure integrity.

So... we need a library that can handle integers, a library to handle floating points, a library to handle arrays, etc.

Details

Operating System:

Linux

Category:

Development

Mode:

Console

MySQL CREATE USER features!

Alexis Wilke — Sat, 05 Dec 2009 06:56:03 +0000

Today, I had to fix an installation of MySQL.

There were several problems, and I finally got it to work. Somehow, I had to run some commands manually to cleanly shutdown the cluster server and then re-run the configuration script with dpkg:

Details

Operating System:

Drupal

Category:

Development

Mode:

Daemon

Negative constant ... was passed to a negative sink

Alexis Wilke — Sat, 05 Dec 2009 01:59:42 +0000

Today, as I was working with Coverity, I got this one message...

Negative constant passed to a negative sink.

Although I understood the meaning, I thought that this message was very confusing, How about:

Unexpected negative value in parameter #<position>

Details

Operating System:

MS-Windows

Category:

Development

Mode:

Console

TOC test without editor

Alexis Wilke — Thu, 03 Dec 2009 09:39:45 +0000

title 1

Test A

title 2

Testing B

title 3

Weird format

Details

Operating System:

Drupal

Category:

Development

Mode:

Browser

Auto-Vacuum not working? (and solution)

Alexis Wilke — Sun, 08 Nov 2009 23:26:01 +0000

Since I manage multiple computers and each run a PostgreSQL database system, I can see discrepancies between versions. (i.e. newer versions fix problems in older versions.)

Details

Operating System:

Drupal

Operating System:

Linux

Operating System:

Mac OS/X

Operating System:

MS-Windows

Category:

Storage

Mode:

Daemon

Taxonomy error generated from invalid nodes

Alexis Wilke — Sun, 01 Nov 2009 06:47:47 +0000

Today I ran in an error that looked like this:

Invalid argument supplied for foreach() in <path>/modules/taxonomy/taxonomy.module on line 1214.

The line number may vary depending on the version you are using. At the time, I had Drupal 6.14 and the line number was 1214.

The problem is with a node that has an invalid definition of its taxonomy field. In other words, the $node->taxonomy is not defined. If it were an empty array, the function would not fail.

Details

Operating System:

Drupal

Category:

Development

Category:

Storage

Category:

Web Server

Mode:

Browser

OpenSSL and PostgreSQL conflict in PHP

Alexis Wilke — Sun, 25 Oct 2009 23:29:20 +0000

All of last week I've been looking for the solution to a bug in one of my numerous websites.

The problem was that after registering, a user would get an error saying that the PostgreSQL connection was lost. I had never had that with Drupal and yet, it would be 100% consistent.

I tested the new code several times and had no problems with it, so I was really dismayed that all of a sudden it stopped working.

Details

Operating System:

Drupal

Category:

Development

Mode:

Daemon

3rd button of one of my SGI gray mouse dies...

Alexis Wilke — Sat, 17 Oct 2009 03:29:15 +0000

I've got those 3 button mice from SGI as I was working with Indy's and O2's. I also have keyboards. Those are real good quality!

Yesterday, I tried to right click and somehow, nothing happened. At first I thought maybe it was X going banana, but trying again and restarting did not change anything. I reset my KVM too, just in case. Still nothing.

Details

Operating System:

Linux

Category:

Desktop

Mode:

GUI

Freeze Pan — How do you lock a row and/or column in a long Excel spreadsheet?

Alexis Wilke — Tue, 13 Oct 2009 07:37:51 +0000

I have been wondering how to lock a few rows and/or columns on a side in Excel. I have seen that being done many times, but did not know how to do it myself.

In the Windows menu (Before Office 2007) and in the View menu (Since Office 2007) you will find an option named Freeze Panes. You have three selections:

Freeze the selected top rows
Freeze the selected left columns
Freeze the selected top rows and left columns

If you just need one row and/or column, place your cursor in the A1 cell.

Details

Operating System:

MS-Windows

Category:

Other

Mode:

GUI

Using your firewall with Postfix

Alexis Wilke — Mon, 12 Oct 2009 09:01:45 +0000

After a little while (very little) our mail server gets quite clogged. It does not cause much problem to our server, however, legal mail server will have a hard time to connect because all of those illegal mail server connect thousands of times to try sending us spam.

To give you an example, I blocked less than 10 IPs today and I got over 5,000 hits blocked within about 12 hours. That's to give you a picture of the badness of those scam robots.

Details

Operating System:

Linux

Category:

Transfer

Mode:

Daemon

wsprintf() limit under MS-Windows

Alexis Wilke — Wed, 30 Sep 2009 23:55:38 +0000

Today I wanted to check out a set of floating value in my Visual C++ development environment.

You can use the OutputDebugString() to print a debug string in the VC++ output window when running a software. This is quite handy, but when working in C++, string handling can be tedious. I need to create a message and wrote something similar to this:

wchar_t msg[128];
swprintf(msg, "Float: %f\n", my_float);
...

Details

Operating System:

MS-Windows

Category:

Development

Mode:

GUI

AddThis weird behaviors

Alexis Wilke — Thu, 24 Sep 2009 20:01:04 +0000

I just switched my websites from one server to another and noticed that on my main company site (http://www.m2osw.com) I would get a # at the end of the URL. Automatically added somehow. Thinking that could be a bad guy I checked the code and could not really see anything.

Hitting "Back" once, I noticed that the # would be transformed to #atssh-digg. I don't have anything specific about digg on that page except the AddThis button. That adds Digg among some 150 different systems where you can share my pages.

Details

Operating System:

Drupal

Operating System:

Linux

Operating System:

Mac OS/X

Operating System:

MS-Windows

Category:

Web Server

Mode:

Browser

Moving a website from one server to another

Alexis Wilke — Wed, 23 Sep 2009 07:08:17 +0000

Moving a website to a new server

Now and again, you have to move a website from one server to another.

There are good and bad things about that, the main problem is with dynamic websites. Why is that? Simple: a dynamic website expects to access a database and if you hit the wrong server, that will go bad.

What's the best solution?

Details

Operating System:

Linux

Category:

Transfer

Category:

Web Server

Mode:

Daemon