The Linux Page

Help other users realize that everything is possible, especially avoiding Windows for their own personal use.

Welcome to The Linux Page


Fox Trot by Bill Amend. Click to enlarge.
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This site is a collection of my own work with Linux. Certain things are easy, others take time to decipher and if I ever need to repeat the work (which usually happens!), then I need to remember everything by memory or... have a site with all the steps taken and to take again.

The following are my most recent posts:

I just upgraded an Ubuntu server from version 9.10 (Karmic Koala) to 10.04 (Lucid Lynx) and started getting a strange error about some package dependencies being unmet. I'm sure I did not intentionally install those packages, so as I was upgrading, I would imagine that they should have been removed automatically if required.

  # apt-get install <some-module>
  Reading package lists... Done
  Building dependency tree      
  Reading state information... Done
  You might want to run `apt-get -f install' to correct these:
  The following packages have unmet dependencies:

Today I did an upgrade of a server from 9.10 to 10.04. We were on a server version before upgrading to 9.10 but we could not directly upgrade to 10.04 (working upgrade paths are very specific; see a list here: https://help.ubuntu.com/community/UpgradeNotes )

The most surprising part was the python script at the end.

  /usr/bin/python /tmp/unique-folder/lucid --mode=server --frontend=DistUpgradeViewText

The command line itself is not specifically strange. However, the behavior at the end of the script is a bit strange, mainly because I hadn't see it before. Last time the upgrade was

When creating an unbound text in MS-Access it is not constrained in length. The text limit you get when the field is bound to the database table is really neat, but there is not direct way to access that code (it's probably something hard coded in the MS-Access system.)

This means you have to re-implement the behavior.

I found this page Unbound text box: limiting entry length which has a very good solution. Just in case the page disappears, there is what I use (a simplified version that doesn't manage errors because I do not like that — errors are not supposed to happen, when they do,

Problem

I have to use Qt these days. It's a good system, but there are a few tricks to know about.

As I was starting to write a test, the test needed a lot of numbers but nothing much otherwise. So I decided to limit the #include to a minimum by deleting all of those that I did not need.

The result was this error:

"Cannot create a QWidget when no GUI is being used"

I looked into it and sure enough people talking about it say: Well... where is your GUI?

Great, but I don't see how that helps me in fixing the problem, does it do it for you? Neither?!

Solution

...

Until now, I only had to upgrade my PostgreSQL databases between computers so I would pg_dump + pg_restore the databases.

However, PostgreSQL offers a tool named pg_upgradecluster that does that work for you, plus it will copy all the different things that pg_dump doesn't always catch such as functions, existing users, etc.

This sounds all good...

So I ran it against our cluster of 298 databases and got a little surprise: it takes about 10 minutes to run on one database, whatever its size. Yes! 10 minutes. Our big database has over 1 million rows, the smallest have a few hundred. Impressive

Connection problem with Shredder

Today I got a little surprised by Shredder (the base used to build Thunderbird.)

Somehow, the certificates for my mail server had reached maturation (i.e. it was showing an end date as of today.)

On each connection to the server I would get the following error:

<name>: uses an invalid security certificate
The certificate is not trusted because it is self signed.
(Error code: sec_error_ca_cert_invalid)

Interestingly enough, I search on this error and mainly found things about FireFox and SeaMonkey instead of Thunderbird (and nothing about

Today I found a table describing the keystrokes you can use to generate different letters in another language than the bare ASCII set used in the US. For example, it is nice to use "à" in French whenever necessary because "à" (a preposition) has nothing to do with "a" (a conjugated verb).

Microsoft includes that feature for most of their software. It may not work in all software, although you can always open wordpad and then copy and paste the output. (Notepad is not enough, it does not support UTF-8 or Unicode too well.)

...

Somehow I receive many weird requests from one of Googlebot's. These use some very strange HTTP header, if I can even call that a header! modsecurity blocks all of them at once, but it just seems very strange since it has nothing to do with HTTP.

The two requests I have seen go like this:

0x16 0x03 0x01

0x80 0x2B 0x03 0x01

As you can see I show you the hexadecimal codes because these are controls!!! (Ctrl-V, Ctrl-C, Ctrl-A in the first request, and PAD, +, Ctrl-C, Ctrl-A)

I just have no idea what that is. I'm glad that modsecurity kicks those request out, but I'm wondering why am I

I got a problem with Qt that took me a whole day to fix!

I created a widget with many children. At first I used the QVBoxLayout and QHBoxLayout to lay out the child buttons in a grid like layout without paying much attention to the details. This was not too bad except that somehow the system picked up the smallest possible size for each button. Once I put a minimum size, it was better, but still not giving me much control in comparison to the specification for my project.

So at that point I looked around to learn how to create your own layout. Got the idea to look at the existing layout

I've been using Drupal for a while and only now started to notice a problem with the cache of JavaScript code. In general, I don't cache the JS since they are not dynamic files. But we do that with Snap!.

The Apache mime module offers two options: AddType and AddEncoding

Both options are used in a similar way meaning that both react on file extensions. When a match is found, the corresponding MIME type or content encoding is attached to the content being sent.

If you install the MIME module, it will attempt encode data properly for the most general case, but not all cases. That is, it does

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