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By Matthieu, 2017-04-10 20:07

Windows Default Soundfont

Arachna Soundfont

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By Matthieu, 2015-12-09 10:40

When setting up Postfix on Ubuntu/Debian as “Internet Site with smarthost” to use an external smtp relay, automatic e-mails intended for “root” (such as cron job error reports) get sent out to the smarthost with a To: address of [email protected]. This can cause a problem as the smarthost doesn’t know where to deliver these messages to, since myhost.mydomain.com has no MX record.

The fix for this is (go figure) in the Postfix README:

Delivering some but not all accounts locally

A drawback of sending mail as “[email protected]” (instead of “[email protected]”) is that mail for “root” and other system accounts is also sent to the central mailhost. In order to deliver such accounts locally, you can set up virtual aliases as follows:

1 /etc/postfix/main.cf:
2     virtual_alias_maps = hash:/etc/postfix/virtual
3 
4 /etc/postfix/virtual:
5     root     [email protected]
6     . . .

Translation:

• Line 5: As described in the virtual(5) manual page, the bare name “root” matches “[email protected]” when “site” is equal to $myorigin, when “site” is listed in $mydestination, or when it matches $inet_interfaces or $proxy_interfaces.

Execute the command “postmap /etc/postfix/virtual” after editing the file.

Oddly, just adding the line

root: [email protected]

to /etc/aliases doesn’t work. You really need to do the steps outlined in the manual.

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By Matthieu, 2015-04-07 21:18

It’s really cool what we can do with computers these days. I generally take technology for granted, but sometimes I am just in awe of what is possible.

With the ubiquity of the Internet
It’s all too easy to forget
How amazing it is, that with relative ease –
Just a few strokes of the keys
A sysadmin can ssh to a box running Unix
On the other side of the world, or just across town.
And with just a few clicks
Bounce that Windows box that’s gone down.

Image credit: https://www.flickr.com/photos/stars6/4381851322/

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By Matthieu, 2015-03-29 23:40

I feel ready for the OPS235 exam. There are a few areas I need to brush up on, but overall I feel I have a grasp  of most of the course content.

Strengths

• CentOS installation
• KVM administration via GUI
• Package/software installation and updates
• tar and file archiving/management
• fstab and partition management

Weaknesses

• Knowledge of specific commands and arguments/switches (rely on man pages)
  • iptables syntax
  • lvm commands
• CentOS/RedHat-specific commands and conventions (used to Debian/Ubuntu)
• SELinux
• Memorization of .conf file structures

Exam review topics

• KVM network configuration
• User and group management

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By Matthieu, 2015-03-29 23:30

Software installed

Apache

Apache is an open-source web server software maintained by the Apache Software Foundation and the open-source community. It can be extended using modules, and is well-documented and well-supported. It is usually the de-facto standard Web server on Linux, although lately new and customized Web servers such as nginx have been becoming more popular for dynamic, high-traffic sites.

PHP

PHP is a server-side scripting language mainly used for web development. By writing PHP rather than plain HTML, developers are able to create pages that are dynamically generated by the server on the fly depending on parameters provided. The Zend PHP interpreter is open-source software, and is available as a module for multiple Web servers on Linux, Windows, BSD and other OSes.

MySQL

MySQL is an open source relational database management system (RDBMS). It is open-source software, released under the GPL and sponsored by Oracle Corporation. The software is available at no cost, although there are also some paid versions. It has widespread use in Web applications, such as WordPress and MediaWiki, and is also used by large sites such as Facebook and YouTube.

LAMP stack

Together, CentOS (Linux), Apache, MySQL and PHP form an implementation of a LAMP stack. This stack provides a consistent, portable environment for Web developers.

WordPress

WordPress is an open-source blogging platform and CMS. It is written in PHP, and uses a MySQL database for text content storage and metadata. It provides an easy-to-use user interface, and is highly extensible and customizable with a large number of user-creatable themes and plugins. WordPress powers some prominent sites such as Forbes.com, vogue.com and nationalpost.com.

Problems encountered during installation

• The systemctl command was not available, since this install of CentOS is using upstart rather than systemd.
• There was no default index page created during the install of httpd. As a result, accessing HTTP on the Centos3 VM server gave an HTTP error 403 (Access denied) – the default Apache configuration denies directory listings.
• The c6host machine was not able to access the HTTP service on centos3 because its iptables was not configured to allow inbound traffic on port 80.
• When configuring iptables on centos3, running iptables -A INPUT -p tcp –dport 80 -j ACCEPT was notsufficient.
  • The -A option appends the rule to the end of the INPUT chain, however, there was a pre-existing explicit rule rejecting all packets.

     REJECT     all  --  0.0.0.0/0            0.0.0.0/0           reject-with icmp-host-prohibited

  • To move the new rule above the reject rule, the incorrect rule had to be removed by running iptables -D INPUT -p tcp –dport 80 -j ACCEPT
  • Then, find the line numbers by running iptables -L –line-numbers

     Chain INPUT (policy ACCEPT)
     num  target     prot opt source               destination
     1    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
     2    ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0
     3    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
     4    ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:22
     5    REJECT     all  --  0.0.0.0/0            0.0.0.0/0           reject-with icmp-host-prohibited

  • Use iptables -I INPUT 5 -p tcp –dport 80 -j ACCEPT to insert the new rule above the existing rule 5.
  • Running iptables -L –line-numbers again gives the following output:

    Chain INPUT (policy ACCEPT)
    num  target     prot opt source               destination
    1    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
    2    ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0
    3    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
    4    ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:22
    5    ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:80
    6    REJECT     all  --  0.0.0.0/0            0.0.0.0/0           reject-with icmp-host-prohibited

• The contents of the WordPress .tar.gz file were extracted to /root/wordpress. Moving this directory to /var/www/html resulted in the Apache process not being able to read the wordpress subdirectory. Copying (cp -R) avoids this issue.
• When configuring the WordPress connection to MySQL, the WordPress documentation said to run the query

  mysql> GRANT ALL PRIVILEGES ON databasename.* TO "wordpressusername"@"hostname"
      -> IDENTIFIED BY "password";

  to allow access to the database. However, since the MySQL server and Apache/WordPress are installed on the same host, we need to use “localhost” rather than “centos3” for the hostname.

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By Matthieu, 2014-10-15 08:53

Not sure of the implications of this/best practices, but I just added

$_SERVER['HTTPS'] = 'on';

to my index.php.

Reason for this is that I am running a php app behind a reverse proxy, with the connection between the app server and the reverse proxy being plain HTTP, but the connection between the client and the reverse proxy is HTTPS.

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By Matthieu, 2014-08-02 21:37

I don’t really play DVDs on my PCs much anymore, but my brother have me the full boxed set of Freaks and Geeks (great show, cancelled too soon). Running on a fresh install of Ubuntu 14.04, I popped in the DVD and was prompted by “Video Player” aka Totem to install some additional codecs. I obliged, but after the installation, the DVD still wouldn’t play. It turns out that because of legal issues, the libdvdcss2 library is no longer included in the Ubuntu repositories. However, the libdvdread4 package does provide a script to easily install it.

Once you have libdvdread4 installed, run following script:

# sudo /usr/share/doc/libdvdread4/install-css.sh

Restart your video player and enjoy your DVD.

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By Matthieu, 2014-03-22 15:03

Windows XP is going out of support next month.. This means Microsoft will no longer provide security updates or any patches for the OS, leaving users of the 12-year old version of Windows more vulnerable to emerging threats.

On this occasion, let’s take a moment to put dear old WinXP’s age in perspective. But first, some mood music:

When Windows XP was released…

Bill Gates was still CEO of Microsoft.

Gates with his new baby. Also Alias.

Friends, Buffy the Vampire Slayer, The X-Files, Frasier and Sex and the City were still airing new episodes.

Vampires were still scary.

The one where Monica and Chandler are married and Rachel is freaking out.

We had yet to see shows like The Office, Arrested Development, House and How I Met Your Mother.

There was no Gregory House in 2001.

The current-gen iMac had a CRT display.

This was the competition.

There was only The Matrix.

This was true in 2001.

The “War on Terror” had only just begun.

The President of the USA.

The BlackBerry 950 was the current model.

Portable productivity for the business professional.

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By Matthieu, 2014-01-09 19:28

Being  a “computer” guy, I often get asked all kinds of questions related to technology.

Some questions that come up quite often are “What kind of laptop should I buy?” or “What do you think of [insert name of tablet]?” or “My laptop is old. I need a new one, but I’m thinking of Windows 8/iPad/Android instead. What are your thoughts?”

The best advice I can offer anyone is:

What are you looking for in your electronic device?

Whether you’re shopping for a car, a house, a phone etc. it helps to know what you’re looking for. If you work in construction and need to haul 2x4s and bricks and things fairly often, a sport coupé is probably not the right car for you. Likewise, when picking a mobile computing device, you should think about what you need the device to be able to do. So, before shopping, take a step back and evaluate your needs and wants for your mobile computer.

So, before even looking at the latest Best Buy flyer – a few questions to ponder:

• What are the workloads? Word processing, web browsing, YouTube (HD), e-mail, gaming, music, photo editing, etc.
• What kind of apps do you want to use?
• Where will you be using the device? In class? On the train/bus? In meetings? At your desk?
• Will you be carrying the device a lot? In a bag?
• Are you looking for something stylish? flashy? durable?
• Do you really need a portable device? Desktop computers are still a good option, and there are interesting all-in-one options.

There are all kinds of technology form factors today, and more being created all the time. Everyone’s needs and preferences are different, but there’s probably a device that’s just right.

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By Matthieu, 2013-09-16 02:17

– Are you mad at your computer?
– I type with purpose.

Is a mechanical keyboard really better to type on?
I’m not sure yet but it certainly is louder. It’s really loud. I washed this keyboard this morning, getting rid of 20 years of dust and grime. Hopefully I didn’t damage the electronics with all the water. It seems OK now, but earlier I was getting some double letters. The model M is a buckling spring keyboard. Some say that’s the best type of mechanical keyboard. Never tried others myself – Cherry MX switches and the like. Those fancy keyboards from Filco and Das Keyboard look great, but I still can’t see myself paying $100 for an input device. I suppose I don’t really spend enough time actually typing for it to be worth it. This particular Model M was salvaged from the trash bin. It’s a cool white colour and not the usual grey/beige. It’s also branded Ambra (a Canadian IBM brand) rather than IBM or Lexmark. Manufacturing date is 1993. I’m also currently using an IBM PS/2 mouse. It’s actually a fantastic quality “ball” mouse, way better than the late cheap OEM mice that came with PCs in the early ’00s before optical mice became the norm. The mouse is light, the cursor responds great… if only this thing had a scroll wheel.

OK, now that I’ve typed a few lines on the mechanical keyboard, let’s try the total opposite.

Here we go, typing on an Apple Aluminium keyboard. Chiclet-style keys, virtually flat – identical to MacBook keyboards. Very different feel when typing, obviously. Hands are also in a different position, this keyboard is very low to the table. I’m actually not sure which one I prefer. I feel like there are a lot more “shocks” going through my hand when my fingers hit the keys on the Apple keyboard, since the key travel isn’t very far. This keyboard is actually surprisingly loud, especially the space bar. Having volume function keys is nice.

Let’s try the IBM again.

Back on the Model M. A lot more noise. How about the typing feel? It feels pretty good. More natural to type on here than on the Apple. I had read online something about not having to press the keys as far since the keys actuate before actually being pushed in all the way. Not sure if that’s how I’d describe the feeling of typing on here. The thing that strikes me most is the really springy feel – which is to be expected, after all, the keys each have a physical spring underneath them. I’m going to have to try a typing test using both keyboards to see how many WPM I get. The model M seems to have issues with Backspace sometimes. Probably due to the PS2 to USB adapter I had to use to connect it to the laptop.