This Week I Learned - 2017 Week 16

Last week post or the regular whole series.

Minor hiccups due to sleeping schedule messed up my daily routine. Nothing but readjustment to get back on track. Switching different way of monitoring your habits did not produced the result needed. Furthermore, you should unwind during the weekend. If you need to use the Internet, write down the items you want to research instead of impulsively googling. Maybe I should just switch to dumb phone, nothing but for calls and SMS, like the old days. But it may not be a feasible solution and impractical.

#1 My whole development life in a circle where I have to encounter XXX again in the current development works. There is a write up on the origins of XXX as FIXME (via HN). Reason that we use XXX is easily greppable comment prefixes.

#2 How to handle Perl class-level variables. Two ways. (1) Lexical variable scoped (via subroutine) and (2) package variable. Simple concept that took me a while to finally realize and understand it.
# (1)
my $foo = 123;
sub get_foo { $foo }

# (2)
our $fubb = 456;

On a related note, found a list of Perl modules related to testing. There is so many modules that I haven't try out yet. So many things to try out, yet so little time.

#3 How do you remove all files except one? Seems hard yet so simple, if you know and remember how it works. Only on a rare instance you will encounter this. Typically we just move the file to different folder and delete the source folder.
$ shopt -s extglob 
$ rm -- !(file.txt)

#6 "If you haven't experienced true solitude yet, go find some. It's pretty grounding." (via HN) It's not a man against the wild but rather a man seeking himself through the solitude of nature. It has been so long that we ever lie down and look up the sky and enjoy the stars?

#7 "Colour is in the eye of the beholder". Interesting that our vocabulary influences how we perceive colours. Himba people have interesting vocabulary for colours, for example zoozu (dark colours and black), vapa (light colours and white), borou (green with blue and purple), dumbu (beige with yellow and some light green), and serandu (red with orange and pink). You can read more on this presentation, The Development of Color Categories in Two Languages: a longitudinal study.

#8 If you're facing problem with Google Chrome whenever you're opening new page but it took a while to load while waiting for "Resolving host...". Clear the DNS cache in Chrome. Seems to resolve the lagging issue for me and making browsing experience bearable.

Unable to Mount USB Thumb Drive in Nautilus - Physical Block Size Mismatch

Before I can proceed to setup my tiny homelab machine, Kabini, I need to burn the installation media to the USB thumb drive. However, when the thumb drive was plugged in, Nautilus can't seem to mount it although the kernel message did indicate device `/dev/sdc` did exists and mounted.

Checking through GParted, the default GUI partition tool in GNU/Linux shown that "The driver descriptor says the physical block size is 2048, but Linux says it is 512 bytes"


As usual, SO gave us the root cause and solution to rectify this block size error issue. It seems that I may accidentally wrote to the USB thumb drive using the wrong parameter through `dd` command. To fix this, we need update the thumb drive's partition to the right block size. Running the command below did resolve the issue for me.
$ sudo dd if=/dev/zero of=/dev/sdc bs=2048 count=32
32+0 records in
32+0 records out
65536 bytes (66 kB, 64 KiB) copied, 0.00655332 s, 10.0 MB/s

Once the corrupted block issue have been resolved, go back to GParted and refresh the thumb drive. GParted will prompt you to create a new partition table.


After we have created the partition table, Nautilus will show a proper mounted thumb drive. See screenshot below.


Download the Ubuntu installation ISO file. I'm downloading both the mini and Ubuntu server 17.04 ISO file. This is the time where torrent really shine where I can achieve the speed of 3.02 MB/s, a feat not doable even using parallel HTTP connection using download manager like Aria2.



Next, burn the ISO using the Startup Disk Creator. Load the ISO file as the source disc image and burn it to your thumb drive.


In the past I always used dd command line utility to burn ISO. Little I realized once you've done burning, you can test the thumb drive.


Verification is done by QEMU, hosted hypervisor. If you can see below installation menu, then the thumb drive have been burned and can boot up correctly.


You can achieve similar result through the command line command below. X is the alphabet of your thumb drive.
$ qemu-system-x86_64 -hda /dev/sdX

This Week I Learned - 2017 Week 15

Last week post or you can browse through the whole series.

While debugging a Makefile, I accidentally `rm -rf` my home folder. Lesson learned, always backup and sync your changes regularly. Nevertheless, it's always a good fresh start when your home folder contains not a single file or folder. Good that you have a weekly clean up of your machine, review, keep, or remove. Otherwise, there will be a lot of pending left over files.

It has been a while since I work on weekend. The serenity of the environment did improve your productivity ten-folds. There is no sounds other than the air-con, traffic, and your typing sounds. You're basically in the zone, focus solely on the task at hand. No more stupid shenanigan. In hindsight, you have to find or create your own optimal environment and zone. It all starts with a system that leads to a habit, good habits.

#1 How to read more books? Lots of good tips and increasing the volume of books you can read. It's already early April and I only managed to finish 2 books. Not really on track on finishing 12 books this year. Thinking back, reading style, book choices, timing, and context are what causing the slowness. One of the best strategy is to switch different books if you're stuck or bored. Some books need more mental energy to go through it. While reading 2 pages per day can develop a good habit, it's not sufficient fast enough to catch up with my pilling reading list.

#2 Engineer's Disease. The unconscious thought that can lead to arrogant and condescending personality. Maybe because such behaviour "stems from the OCD and emotional detachment our peoples tend to have, mixed in with a good dose of raging insecurity"? Good forum discussions to ponder upon, especially by those working in software development.

#3 Does teenager and adult have different learning capability? Time, available perceived time. Also discipline, attention, and focus. The discussion at HN gave a lot of strategies to attack the problem. Simple daily practice and learning together with different learning strategies. What to learn then? Fundamental. There is an interesting discussion on software development being a dead-end job after 35-40.

#4 On understanding the fundamental of Vim. Before you install any Vim's plugin, best to learn what the default features exists or not.

#5 System Design Primer. If you want to learn how to design large scale systems. However, premature optimization is still evil. Knowing something can be done right doesn't means it should be done now. There are always contexts and constraints. Solutions looking for problems always end up wasting everyone resources. This HN user's experience on scaling your system accurately illustrates such scenario.

#6 Looking busy at work?. Most people don't realize that pretend to work and look busy is actually far more harder than doing the actual work. Faking will deplete you psychologically as your thoughts, actions, and words are not in sync. However, there are always exception. Certain group of people thrive on such behaviour without caring for any forms of repercussion. While some just stuck with mind-numbing boring job. There is a saying by Napoleon Hill which states "If you are not learning while you’re earning, you are cheating yourself out of the better portion of your compensation.” Unless you're stuck with certain constraints, move on. You're not a tree!

#7 LXD finally available for Fedora. Not as native RPM package but through Snap. I'm going to reformat another workstation and install Fedora with it. One less reason to stick with Ubuntu. Only left the DEB package, which I believe, no way Fedora/CentOS/Red Hat is able to dethrone the number of available packages provided by Debian. I'm not looking for rolling release like Arch but availability of different software. Maybe Snap, the universal GNU/Linux package can change that?

Upgrade to Ubuntu 17.04

Just read that Ubuntu 17.04 was supposed to be released today and eager to try it out. While nothing special and significant was added to this release, nevertheless, it's good to have the latest greatest when possible. Furthermore, I've accidentally `rm -rf` my home directory few days back.

Running through the typical upgrade steps.
$ sudo apt-get update
$ sudo apt-get dist-upgrade
$ sudo do-release-upgrade -d

However, upgrade seems to fail due to broken packages, see below. Most likely due to many legacy PPA added for certain kind of special packages.
Calculating the changes

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu

Found the answer to troubleshot this issue. You must keep the upgrade running at the same time, otherwise the `apt.log` file would not be found. I was surprised that I have so many broken and conflicting package. Follow the procedure, I have to manually remove all broken packages. For certain packages, I have to reinstall because it can't find the actual packages. Result below were truncated to save space.
$ grep Broken /var/log/dist-upgrade/apt.log

Broken libdouble-conversion1:amd64 Breaks on libdouble-conversion1v5:amd64 ......
Broken imagemagick-6-common:amd64 Breaks on libmagickcore-6.q16-2:amd64 ......
Broken libgjs0f:amd64 Conflicts on libgjs0e:amd64 < 1.46.0-1 @ii mK >
......

Upgrade was slow as I've just installed LaTeX few days back. Downloading all those `texlive-` packages going to take some times.

This Week I Learned - 2017 Week 14

Last week post or you can go through the whole series.

Proposal have been presented and submitted. Standard feedback received. Nevertheless, better than nothing regardless the quality of the reactions.

#1 GTCafe Studio. Stumbled upon this site while searching for different covers of Guthrie Govan's Emotive Ballad. It's rare these days to find any blog with original good content. Reading through his journal on learning guitar made me reflect back on my decision on donating all my guitars away few years back. Maybe is time to start all over again? Or maybe not? Learning to play an musical instrument is one of the way to escape from mind-numbing daily routines. However, there is a time and place for everything in life. In hindsight, sometimes you just have to move on.

#2 "CentOS is not stable, it is stale". So true that it hurts. For me, as a whole, Fedora provides a better desktop experience than Ubuntu. Yet, I still revert back to Ubuntu on my daily usage. Why? APT is definitely better than YUM and plenty of software selection. Furthermore, LXD works only in Ubuntu and not Fedora. And yes, finally Canonical realized that and declared Ubuntu Unity will be replaced by Gnome 18.04 LTS. Maybe this Ask HN post on feedback for Ubuntu 17.10 from the community have finally sealed the fate for Unity?

I always wonder what would happen if Red Hat decided to use build a distro based on Debian or DPKG package manager instead of creating their own RPM packaging manager? A unified GNU/Linux desktop will come sooner rather than unnecessary fragmentation and efforts. For example, the competition of next generation display server of Mir and Wayland. Yes, I know having options and competitions is good for progress. But the priority and effort should be on fixing the damn display drivers performance and stability issues. Fragmentation leads to duplication of works.

#3 Five great Perl programming techniques to make your life fun again. An old article, 11 years ago but everything described there is as relevant as today especially iteration using `map` and `grep` and Dispatch Table as illustrated in example below. As Perl does not have `switch` statement, hence using Dispatch Table is a good Perl design patternMark Jason Dominus, in his book, Higher-Order Perl also devoted a whole chapter (PDF) on this matter.
my $dispatch_for = {
   a => \&display_a,
   b => \&display_b,
   q => sub { ReadMode('normal'); exit(0) },
   DEFAULT => sub { print "That key does nothing\n"; },
};

my $func = $dispatch_for->{$char} || $dispatch_for->{DEFAULT};
$func->();

#4 Perl 5 Internals (PDF). Interesting reading on the intricacy part of the Perl itself. It was brought to my attention that Perl is a bytecode compiler, not an interpreter or a compiler.

#5 The 'g' key shortcuts in Vim. You will learn something new everyday, there are so many key bindings. Surprisingly, I only knew and regularly use two. Really needs to refresh and relearn this.

This Week I Learned - 2017 Week 13

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Night owl turned early bird messed up my sleep cycle badly. Nevertheless, the draft report have been completed and waiting for submission.

#1 Feeling nostalgia after watching the unboxing video of IBM PC AT and Model M. The sounds of the diskette reading and loading the data reminded me of the good old days of early computing period. I'm not sure what happened to our XT 8088 but I'm surely wish I can see it again and try to boot it up again. I did once during my college days but would really love to do it again after all these years. Back in those days, XT 286 is my dream machine and how I wish we have the financial means to upgrade to it. 


#2 Lots of Docker debugging for the past week and I learned quite a lot. It's the right time to setup my virtualization machine (more on this in coming week) and start looking into Docker.

When using Docker Compose, use `docker-compose ps` instead of `docker ps`. While both commands show the listing of the available containers, the former command will only list containers declared in the `docker-compose.yml` file, a subset of the all available containers. Best to go through all the Docker Compose CLI command line parameters.

Next, you want to read (or search) the content of a file in the docker container. See the example below. Yes, I know you can just simply use the `grep` command directly.
$ docker exec -i mycontainer cat /etc/hosts | grep localhost

#3 Setting up multiple SSL certificates using one IP address in Nginx. And also how to verify and read SSL certificate info from the console. Next is to configure Google Chrome to accept invalid certificate from localhost. Copy and paste `chrome://flags/#allow-insecure-localhost` to the address text box to access the setting. Instruction as shown below.