Entries posted in October 2014

A brief introduction to freebsd

Wednesday, 29 October 2014

I've spent the past thirty minutes installing FreeBSD as a KVM guest. This mostly involved fetching the ISO (I chose the latest stable release 10.0), and accepting all the defaults. A pleasant experience.

As I'm running KVM inside screen I wanted to see the boot prompt, etc, via the serial console, which took two distinct steps:

  • Enabling the serial console - which lets boot stuff show up
  • Enabling a login prompt on the serial console in case I screw up the networking.

To configure boot messages to display via the serial console, issue the following command as the superuser:

 # echo 'console="comconsole"' >> /boot/loader.conf

To get a login: prompt you'll want to edit /etc/ttys and change "off" to "on" and "dialup" to "vt100" for the ttyu0 entry. Once you've done that reload init via:

 # kill -HUP 1

Enable remote root logins, if you're brave, or disable PAM and password authentication if you're sensible:

 vi /etc/ssh/sshd_config
 /etc/rc.d/sshd restart

Configure the system to allow binary package-installation - to be honest I was hazy on why this was required, but I ran the two command and it all worked out:


Now you may install a package via a simple command such as:

 pkg add screen

Removing packages you no longer want is as simple as using the delete option:

 pkg delete curl

You can see installed packages via "pkg info", and there are more options to be found via "pkg help". In the future you can apply updates via:

 pkg update && pkg upgrade

Finally I've installed 10.0-RELEASE which can be upgraded in the future via "freebsd-update" - This seems to boil down to "freebsd-update fetch" and "freebsd-update install" but I'm hazy on that just yet. For the moment you can see your installed version via:

 uname -a ; freebsd-version

Expect my future CPAN releases, etc, to be tested on FreeBSD too now :)



On writing test-cases and testsuites.

Wednesday, 22 October 2014

Last night I mostly patched my local copy of less to build and link against the PCRE regular expression library.

I've wanted to do that for a while, and reading Raymond Chen's blog post last night made me try it out.

The patch was small and pretty neat, and I'm familiar with GNU less having patched it in the past. But it doesn't contain tests.

Test cases are hard. Many programs, such as less, are used interactively which makes writing a scaffold hard. Other programs suffer from a similar fate - I'm not sure how you'd even test a web browser such as Firefox these days - mangleme would catch some things, eventually, but the interactive stuff? No clue.

In the past MySQL had a free set of test cases, but my memory is that Oracle locked them up. SQLite is famous for its decent test coverage. But off the top of my head I can't think of other things.

As a topical example there don't seem to be decent test-cases for either bash or openssl. If it compiles it works, more or less.

I did start writing some HTTP-server test cases a while back, but that was just to automate security attacks. e.g. Firing requests like:

GET /../../../etc/passwd HTTP/1.0
GET //....//....//....//etc/passwd HTTP/1.0

(It's amazing how many toy HTTP server components included in projects and products don't have decent HTTP-servers.)

I could imagine that being vaguely useful, especially because it is testing the protocol-handling rather than a project-specific codebase.

Anyway, I'm thinking writing test cases for things is good, but struggling to think of a decent place to start. The project has to be:

  • Non-interactive.
  • Open source.
  • Widely used - to make it a useful contribution.
  • Not written in some fancy language.
  • Open to receiving submissions.

Comments welcome; but better yet why not think about the test-coverage of any of your own packages and projects...?



On the names we use in email

Saturday, 18 October 2014

Yesterday I received a small rush of SPAM mails, all of which were 419 scams, and all of them sent by "Mrs Elizabeth PETERSEN".

It struck me that I can't think of ever receiving a legitimate mail from a "Mrs XXX [YYY]", but I was too busy to check.

Today I've done so. Of the 38,553 emails I've received during the month of October 2014 I've got a hell of a lot of mails with a From address including a "Mrs" prefix:

"Mrs.Clanzo Amaki" <marilobouabre14@yahoo.co.jp>
"Mrs Sarah Mamadou"<investment@payment.com>
"Mrs Abia Abrahim" <missfatimajinnah@yahoo.co.jp>
"Mrs. Josie Wilson" <linn3_2008@yahoo.co.jp>
"Mrs. Theresa Luis"<tomaslima@jorgelima.com>

There are thousands more. Not a single one of them was legitimate.

I have one false-positive when repeating the search for a Mr-prefix. I have one friend who has set his sender-address to "Mr Bob Smith", which always reads weirdly to me, but every single other email with a Mr-prefix was SPAM.

I'm not going to use this in any way, since I'm happy with my mail-filtering setup, but it was interesting observation.

Names are funny. My wife changed her surname post-marriage, but that was done largely on the basis that introducing herself as "Doctor Kemp" was simpler than "Doctor Foreign-Name", she'd certainly never introduce herself ever as Mrs Kemp.

Trivia: In Finnish the word for "Man" and "Husband" is the same (mies), but the word for "Woman" (nainen) is different than the word for "Wife" (vaimo).



Writing your own e-books is useful

Wednesday, 8 October 2014

Before our recent trip to Poland I took the time to create my own e-book, containing the names/addresses of people to whom we wanted to send postcards.

Authoring ebooks is simple, and this was a useful use. (Ordinarily I'd have my contacts on my phone, but I deliberately left it at home ..)

I did mean to copy and paste some notes from wikipedia about transport, tourist destinations, etc, into a brief guide. But I forgot.

In other news the toy virtual machine I hacked together got a decent series of updates, allowing you to embed it and add your own custom opcode(s) easily. That was neat, and fell out naturely from the switch to using function-pointers for the opcode implementation.



Before I forget, a simple virtual machine

Sunday, 5 October 2014

Before I forget I had meant to write about a toy virtual machine which I'ce been playing with.

It is register-based with ten registers, each of which can hold either a string or int, and there are enough instructions to make it fun to use.

I didn't go overboard and write a complete grammer, or a real compiler, but I did do enough that you can compile and execute obvious programs.

First compile from the source to the bytecodes:

$ ./compiler examples/loop.in

Mmm bytecodes are fun:

$ xxd  ./examples/loop.raw
0000000: 3001 1943 6f75 6e74 696e 6720 6672 6f6d  0..Counting from
0000010: 2074 656e 2074 6f20 7a65 726f 3101 0101   ten to zero1...
0000020: 0a00 0102 0100 2201 0102 0201 1226 0030  ......"......&.0
0000030: 0104 446f 6e65 3101 00                   ..Done1..

Now the compiled program can be executed:

$ ./simple-vm ./examples/loop.raw
[stdout] register R01 = Counting from ten to zero
[stdout] register R01 = 9 [Hex:0009]
[stdout] register R01 = 8 [Hex:0008]
[stdout] register R01 = 7 [Hex:0007]
[stdout] register R01 = 6 [Hex:0006]
[stdout] register R01 = 5 [Hex:0005]
[stdout] register R01 = 4 [Hex:0004]
[stdout] register R01 = 3 [Hex:0003]
[stdout] register R01 = 2 [Hex:0002]
[stdout] register R01 = 1 [Hex:0001]
[stdout] register R01 = 0 [Hex:0000]
[stdout] register R01 = Done

There could be more operations added, but I'm pleased with the general behaviour, and embedding is trivial. The only two things that make this even remotely interesting are:

  • Most toy virtual machines don't cope with labels and jumps. This does.
    • Even though it was a real pain to go patching up the offsets.
    • Having labels be callable before they're defined is pretty mandatory in practice.
  • Most toy virtual machines don't allow integers and strings to be stored in registers.
    • Now I've done that I'm not 100% sure its a good idea.

Anyway that concludes todays computer-fun.



Kraków was nice

Saturday, 4 October 2014

We returned safely from Kraków, despite a somewhat turbulent flight home.

There were many pictures taken, but thus far I've only posted a random night-time shot. Perhaps more will appear in the future.

In other news I've just made a new release of the chronicle blog compiler, So 5.0.7 should shortly appear on CPAN.

The release contains a bunch of minor fixes, and some new facilities relating to templates.

It seems likely that in the future there will be the ability to create "static pages" along with the blog-entries, tag-clouds & etc. The suggestion was raised on the github issue tracker and as a proof of concept I hacked up a solution which works entirely via the chronicle plugin-system, proving that the new development work wasn't a waste of time - especially when combined with the significant speedups in the new codebase.

(ObRandom: Mailed the Debian package-mmaintainer to see if there was interest in changing. Also mailed a couple of people I know who are using the old code to see if they had comments on the new code, or had any compatibility issues. No replies from either, yet. *shrugs*)

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