• Cert on my certifications page
• LinkedIn post
• Cert on Credly

• Cert on my certifications page
• LinkedIn post
• Cert on Credly

Why?

I find the contrast skin is too sterile, the red underline animation when hovering over menu items is too bright, too loud, too much screaming to me. The blue blog post headers weren’t matching with anything else, thus not harmonious with the rest of the colors.

The new skin

The sunrise skin looks more cozy, friendly and inviting imho. The blog posts headers are pink or red and matching with the menu items. I feel this new skin better conveys how I want to present myself online. I didn’t do much blogging last year, this new skin is a good motivation to start writing again.

More updates

I’ve redesigned the showcase (its now called work), about and contact pages. Also made a separate page for certifications. Footer is also updated. I’m happy with the new version of the site. Send me a message to let me know what you think.

The thing that is not yet working as desired are the offline capabilities. It’s only possible to see pages that have already been visited; unvisited pages wil give a 404. I’m going to find out a solution for this. Kurt Lourens has been a major source of inspiration to make this blog available as a PWA.

Getting the data over to the new SSD is a three-step process:

1. I made an image using clonezilla and an external hdd.
2. Installed the new SSD and restored the clonezilla image.
3. Increased the LVM and LUKS partition size to make use of all the space on the SSD.

This article describes step 3 in detail.

:warning: Warning: I always recommend taking backups or snapshots. In case something goes wrong, you’re not permanently burned and you can revert back to the previous setup.

The encrypted partition in this guide is /dev/nvme0n1p3, you should adapt the commands for your own system.

Enlarge an encrypted partition

1. Boot with your (favourite) distro’s live CD.

2. Remove and recreate the existing partition using fdisk.

    sudo fdisk /dev/nvme0n1
   

   This was my fdisk session:

    Opdracht (m voor hulp): p
    Disk /dev/nvme0n1: 931,5 GiB, 1000204886016 bytes, 1953525168 sectors
    Units: sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disklabel type: gpt
    Disk identifier: 3B5990BC-BBAF-41A6-9293-76DC9DAF0017
   
    Apparaat         Start      Einde   Sectoren   Size Type
    /dev/nvme0n1p1    2048    1050623    1048576   512M EFI System
    /dev/nvme0n1p2 1050624    2050047     999424   488M Linux filesystem
    /dev/nvme0n1p3 2050048 1953525134 1951475087 930,5G Linux filesystem
   
    Command (m for help): d
    Partition number (1-3): 3
   
    Command (m for help): n
    Partition number (1-3): 3
   
    Just press enter to use fdisk defaults for partition size, in order to use the full disk (remaning unallocated space)
   

3. Reboot (after changing the partition table with fdisk).

4. Boot the live CD.

5. Mount the LUKS partition with cryptsetup:

    mint ~ # cryptsetup open /dev/nvme0n1p3 cryptdisk
    Enter passphrase for /dev/nvme0n1p3:
   

6. Enlarge the (LVM) Physical Volume with pvresize.

    mint ~ # pvresize /dev/mapper/cryptdisk
      Physical volume "/dev/mapper/cryptdisk" changed
      1 physical volume(s) resized / 0 physical volume(s) not resized
    mint ~ # pvdisplay -m
      --- Physical volume ---
      PV Name               /dev/mapper/cryptdisk
      VG Name               mint-vg
      PV Size               930,53 GiB / not usable 1,69 MiB
      Allocatable           yes
      PE Size               4,00 MiB
      Total PE              238216
      Free PE               116371
      Allocated PE          121845
      PV UUID               JcuPsv-fDo0-zmkX-DN0d-zlg7-hlWY-aerVcg
   
      --- Physical Segments ---
      Physical extent 0 to 117791:
        Logical volume /dev/mint-vg/root
        Logical extents 0 to 117791
      Physical extent 117792 to 121844:
        Logical volume /dev/mint-vg/swap_1
        Logical extents 0 to 4052
      Physical extent 121845 to 238215:
        FREE
   

7. Enlarge the (root) Logical Volume (LV) and file system with lvresize.

   Option -l +100%FREE to take up all the free space. Include option -r to invoke resize2fs for resizing the underlying file system (ext4 in my case).

    mint ~ # lvresize -l +100%FREE -r /dev/mint-vg/root
    fsck from util-linux 2.27.1
    /dev/mapper/mint--vg-root: 3129546/30154752 bestanden (0.5% niet-aaneengesloten), 113461654/120619008 blokken
      Size of logical volume mint-vg/root changed from 460,12 GiB (117792 extents) to 914,70 GiB (234163 extents).
      Logical volume root successfully resized.
    resize2fs 1.42.13 (17-May-2015)
    Van grootte veranderen van bestandssysteem op /dev/mapper/mint--vg-root naar 239782912 blokken (van 4K).
    Het bestandssysteem op /dev/mapper/mint--vg-root is nu 239782912 blokken (van 4K) groot.
   
    mint ~ # lvs
      LV     VG      Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
      root   mint-vg -wi-a----- 914,70g
      swap_1 mint-vg -wi-a-----  15,83g
   

8. Reboot to your encrypted hard drive.

Thanks for reading, let me know in the comments how your experience was.

References

Ubuntu ResizeEncryptedPartitions
ArchLinux Resizing LVM-on-LUKS

Programmer competency matrix

Introducing Sijin Joseph’s programmer competency matrix. This matrix describes four levels of programming skills. It tremendously helps me to assess my current level, to easily see the next level, and how to achieve it. A few remarks:

• Outdated technologies: CVS and SVN version control systems have been replaced with GIT.
• Centered on ‘hard skills’; no mentioning of soft-skills, teamwork, etc.
• Agile skills could also be measured, but there is no mentioning of that (linked to outdated).

Standards

IMHO life is about practising, learning, growing and trusting the process in a continuous fashion in order to raise my personal standards. Whichever standard it is, it is something I can measure and grow towards.

A few inspirational video’s about standards:
Video: Kerwin Rae - What You Tolerate is What You Get

Video: Sway - Level Up (Cahill Extended Mix)

European e-Competence Framework

This framework could be used to assess (IT) competency within organisations. There are four dimensions, 40 competencies, and 30 ICT professional role profiles.

Image: 30 ICT professional role profiles (European model)

Other IT competency frameworks

This blogpost features two frameworks, I know there are several frameworks out there. I use these frameworks to grow to the next level.

Ask yourself: what is the level I am currently playing at? On what level do I hold myself accountable for? Go and do the work 💪.

1) Create a ‘HelloWorld’ file

Don’t use .java as the extension. Java will not recognize the shebang. You can use any other extension, or none.

#!/usr/bin/java --source 11

public class HelloWorld {
    public static void main(String... args) {
      System.out.println("Running Java 11 as script");
    }
}

2) Make sure JDK 11 is installed

Java 11 does not have to be the default.

eimert@EIM ~ $ sudo update-alternatives --config java
Er zijn 5 beschikbare keuzemogelijkheden voor het alternatief java (dat voorziet in /usr/bin/java).

  Keuze        Pad                                             Prioriteit Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      automatische modus
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      handmatige modus
  2            /usr/lib/jvm/java-12-oracle/bin/java             1091      handmatige modus
  3            /usr/lib/jvm/java-8-openjdk-amd64/bin/java       1090      handmatige modus
  4            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      handmatige modus
  5            /usr/lib/jvm/java-9-openjdk-amd64/bin/java       1091      handmatige modus

Druk <enter> om de huidige keuze[*] te behouden, of typ een keuzenummer in: 

3) Run the script

Despite #!/usr/bin/java --source 11 as the first line, simply running java HelloWorld does not work:

eimert@EIM ~ $ java HelloWorld 
Error: Could not find or load main class HelloWorld
Caused by: java.lang.ClassNotFoundException: HelloWorld

Java does compile (under water) and execute when specifying --source 11 as argument.

eimert@EIM ~ $ java --source 11 HelloWorld 
Running Java 11 as script

The file executes with default 0644 permissions:

eimert@EIM ~ $ ls -al HelloWorld 
-rw-r--r-- 1 eimert eimert 164 jun 21 10:24 HelloWorld
eimert@EIM ~ $ java --source 11 HelloWorld 
Running Java 11 as script

Conclusion

Running ‘Java as a script’ gives developers the ability to easily run small utilities on a UNIX system. This feature opens up the possibility to run Java utilities on an UNIX system.

References

• https://github.com/sandermak/java-next-labs
• https://dzone.com/articles/single-file-source-code-with-java-11
• https://www.baeldung.com/java-single-file-source-code

1) Extreme Digitalization in China

I’m impressed by the advances China is making in terms of digitisation. Take WeChat for example, with sub-programmes such as CoffeeBox that have gained tremendous popularity. Payments using face recognition are now commonplace in China, while I haven’t seen this happening (yet) here in The Netherlands. China has a very competitive start-up scene, with long workdays (9-21h, 6 days a week). The competition is fierce, and ideas are copied by competitors. Businesses have to be the first, it does not matter if a product is only partially finished.

2) Machine Ethics

This talk by Nell Watson gives an update on the latest developments in AI.

3) Energy and Education Access for Remote Communities

This keynote was touching because it shows how much the quality of life could be improved by simply installing proper solar panels and lighting in remote (Himalayan) mountain villages.

4) Augmented Reality, Beyond Virtual Objects Floating in Physical Space

This talk gave me new ideas for applying augmented reality in software.

5) Building a Cloud-native Event-driven Microservice Platform for Crypto Currency Trading with Spring Webflux

Erwin de Gier explained how he built BLOX, a cryptocurrency trading platform using reactive technology (Spring Webflux) in a microservices architecture.

6) Boost your API Development with GraphQL & Prisma

Graph databases are new and promising technologies.

7) Taking Security Seriously

Finally a security talk that is enjoyable. Philippe gives several case studies, one is showing the fragility of open source software development.

8) Event-Driven Microservices, the Sense, the Non-sense and a Way Forward

Allard, creator of the Axon framework, provides some common sense for developers on how to go about an event-driven microservice architecture.

9) Innovate using Machine Learning and AI

Altough this is a subtle sales talk/showcase of the AI capabilities offered by AWS, it inspired me with new ideas for new functionalities in apps.

10) How we Built Google Tulip by using Serverless Technology and Machine Learning

Google Tulip was the April fools’ day joke of 2019 by Google (in The Netherlands). The team gave an energetic and humorous presentation. “Looking forward for bouquet scanning capabilities”

In descending order of goodness:

1) adb exec-out run-as nl.eimertvink.smv cat databases/smv_db > smv_db_copy

This is the best and fastest way from stackoverflow. You’ll need your phone connected and a physical phone ^{(with debugging enabled)} or an AVD device ^{(AVD: debugging is enabled by default)}.

A script that simplifies the copy action is humpty-dumpty-android. I’m not going to describe that tool here.
This is the basic way to get the database on your local machine:

1. Copy db to machine:

   adb exec-out run-as nl.eimertvink.smv cat databases/smv_db > smv_db_copy
   

2. View tables:

   eimert@EIM SMV $ sqlite3 smv_db_copy
   (... omitted ...)
   sqlite> .tables
   sqlite>
   

No tables found; empty database file. Read on how to resolve this.

What to do when the database file is empty

You’ll need to call close() on the database instance, to let SQLite write its journal to the database file. For that we’ll create a button that calls close();.

Create a (hidden) button for db.close()

Some Java code that handles the button click:

public class MainActivity extends AppCompatActivity {
        // ... omitted ...

        // Called when the user selects a contextual menu item
        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            switch (item.getItemId()) {
                case R.id.action_close_db:
                    Log.d(TAG, getString(R.string.action_close_db));
                    if (db == null) {
                        Log.e(TAG, "Unable to re-open database instance " + db);
                        Toast.makeText(MainActivity.this, getString(R.string.action_opened_db), Toast.LENGTH_LONG).show();
                    } else if (AppDatabase.isOpen(db)) {
                        Log.d(TAG, "Closing database instance " + db);
                        AppDatabase.close(db);
                        db = null;
                        Toast.makeText(MainActivity.this, getString(R.string.action_closed_db), Toast.LENGTH_SHORT).show();
                    }
                    mode.finish(); // Action picked, so close the contextual menu
                    return true;
                default:
                    return false;
            }
        }
        // ... omitted ...
}

After invoking the button, the db connection cannot be re-opened. The isOpen(db) and close(db) calls refers to these static methods in the AppDatabase class:

public abstract class AppDatabase extends RoomDatabase {
    // ... omitted ...
    public static boolean isOpen(AppDatabase db) {
        return db.isOpen();
    }

    public static void close(AppDatabase db) {
        db.close(); // calls close() on RoomDatabase instance.
    }
}

See this blogpost for more details on how I’ve setup Android Room.

Test the db.close() button

Launch the emulator and start an adb shell:

adb shell

Execute “run-as your.app.realm”:

generic_x86:/ $ run-as nl.eimertvink.smv
generic_x86:/data/data/nl.eimertvink.smv $

Check the database (called smv_db) file size. In this example the actual db has no tables (Size: 4096).

generic_x86:/data/data/nl.eimertvink.smv $ stat databases/smv_db                                                          <
  File: `databases/smv_db'
  Size: 4096	 Blocks: 8	 IO Blocks: 512	regular file
Device: fc00h/64512d	 Inode: 123232	 Links: 1
Access: (660/-rw-rw----)	Uid: (10088/  u0_a88)	Gid: (10088/  u0_a88)
Access: 2019-05-11 12:37:50.711995122
Modify: 2019-05-11 12:37:50.711995122
Change: 2019-05-11 12:56:09.251990576

Click on the button that is calling AppDatabase.close() in the app:

via GIPHY

Again check the database file size. Notice the file has increased in size (from 4096 to to 40960).

generic_x86:/data/data/nl.eimertvink.smv $ stat databases/smv_db                                                          <
  File: `databases/smv_db'
  Size: 40960	 Blocks: 80	 IO Blocks: 512	regular file
Device: fc00h/64512d	 Inode: 123232	 Links: 1
Access: (660/-rw-rw----)	Uid: (10088/  u0_a88)	Gid: (10088/  u0_a88)
Access: 2019-05-11 12:37:50.711995122
Modify: 2019-05-11 12:57:09.121990328
Change: 2019-05-11 12:57:09.121990328

Let’s copy the filled database file to our local machine.

1. Copy db to machine:

   adb exec-out run-as nl.eimertvink.smv cat databases/smv_db > smv_db_copy
   

2. Happy querying:

   eimert@EIM SMV $ sqlite3 smv_db_copy
   (... omitted ...)
   sqlite> .tables
   Question           ScoreDetail        android_metadata
   Rating             TestSession        room_master_table
   sqlite> .quit
   

2) aSQLiteManager

This app gives a SQL console on your phone. You can access the database of other apps when your phone is rooted.

source

3) Android Debug Database

You’ll get a nice web gui on localhost:8080. But in my case I had quite some trouble with the tool (URL not loading). Running adb forward tcp:8080 tcp:8080 solved that issue only a few times.

Conclusion

I’d go for adb exec-out run-as because it is simple and just works.