DEV Community: Efe Ertugrul

NetBSD package manager configuration

Efe Ertugrul — Thu, 10 Mar 2022 04:23:54 +0000

Summary

In this part i'm going to enable built-in package manager and install pkgin. Pkgin is the recommended package manager for NetBSD.
For more information see: PKGIN Website

This part requires active internet connection.

Instructions

1- Start and login to your system.

2- Switch to root user with su command.

3- Go to root's homefolder with cd command. Check with ls command that you're in homefolder. Open .profile dotfile with vi program.

4- In this file find and uncomment export PKG_PATH line by deleting the # character at the start of the line. Save it using :w! command because this file is read-only.

5- This configuration don't require a system restart. It requires a re-login. So logout from all the logged-in users with exit command.

6- Login with root user. (Installing programs requires root privileges)

7- First, install pkgin package manager using command pkg_add -v pkgin .

8- From now on we can use pkgin. Update pkgin database with command pkgin update . Always update pkgin before installing programs.

9- Let's test pkgin by installing vim program. Use command pkgin install vim to install vim. Type Y to continue install. This will download and copy all the necessary files for vim program.

10- After installation is over, test-run the program with command vim. Check if it runs or not.

11- You can also delete installed programs. Remove vim with using pkgin remove vim command.

12- After removal of a program you should also remove unnecessary packages by using pkgin autoremove command.

13- Also use pkgin clean command to clean the cache after an install or uninstall operation.

By the way you should always think programs as potential security vulnerabilities. Especially if you are running your system as a server. So never install any unnecessary programs to a server. Best is always use the programs those come with your operating system. For example use vi instead of vim.

This is the end of NetBSD guide. Now you have a fully functioning minimal NetBSD system. Next is up to you. You can install a Graphical User Interface or configure a Firewall. For more information about NetBSD use the official guide here: NetBSD Guide

NetBSD basic internet configuration

Efe Ertugrul — Thu, 10 Mar 2022 04:23:08 +0000

Summary

In this part i'll show you how to enable NetBSD dhcp daemon for internet connection. Most of the time there is already a dhcp service in your network (your router, virtualbox). So there is no need for manual ip configuration.

If you need to set manual ip configuration for your network or enabling dhcp daemon did not work for you, please visit this website for more information: Setting up TCP/IP on NetBSD in practice

Instructions

1- Start and login to your system.

2- Switch to root user with su command.

3-Open /etc/rc.conf configuration file with vi program.

4- At the end of the file, add dhcpcd=YES configuration and save the file.

5- Restart your system with shutdown -r now command.

6- When your system starts again login and try to ping google with command ping google.com . If you are getting any response, you're connected to internet.

NetBSD non-us keyboard configuration

Efe Ertugrul — Wed, 09 Mar 2022 03:54:33 +0000

Summary

In this part i'm going to configure my non-us keyboard by changing or adding some system configuration files for keyboard. US keyboard users can skip this part.

This part requires you to know basic usage of vi program. If you don't know how to use vi or vim check this website first: NetBSD vi tutorial

vi is almost always pre-installed in every operating system. Learning vi is never a bad idea.

vi basic usage cheatsheet:

Command	Meaning
h	move cursor left
j	move cursor down
k	move cursor up
l	move cursor right
a	add after char
i	add before char
A	add end of line
I	add start of line
o	add below line
O	add above line
dd	delete one line
x	delete one char
:w	save
:q	quit
:wq	save and quit
:w!	force save
:q!	force quit

Instructions

1- Start your system and login.

2- Changing the system configuration requires privilege. So switch to root user with su command.

3- Open wscons.conf file with vi editor.

4- I'm using tr keyboard. So im going to add encoding tr configuration in this file.

5- I'm also going to edit keymaps because my current keyboard doesn't have a less, greater key. (These characters: "<>|"). This requires me to go to /usr/share/wscons/keymaps/ folder. And create a new file named overlay.tr with vi editor. (You can use anything as file name but do not forget it. We're gonna need it)

6- What i'm going to do in this file that i'm going to set some unusable turkish character buttons to bar '|' less '<' and greater '>' characters. For example there is a 'ş' character in my keyboard. It's unusable in console but i might need '|' character so i've added keycode 39 = bar line in this file to set 'ş' button to bar '|' character. I've also set 'ö' and 'ç' buttons to use less '<' and greater '>'. (You can check your full keymap with this command: wsconsctl map | less)

7- Again, open your wscons.conf file with vi editor.

8- Add mapfile /usr/share/wscons/keymaps/overlay.tr configuration and save it.

9- Restart the system with shutdown -r now to load these new keyboard configurations.

10- When system starts, login with user and try your configured buttons. If you can see your characters it means that your keyboard configurations are working.

Next part: Internet connection configuration.

NetBSD minimal installation

Efe Ertugrul — Tue, 08 Mar 2022 05:36:55 +0000

Summary

These are the step by step instructions of installing a minimal NetBSD on a virtual machine. I'm using NetBSD as a mini server. So this installation has no graphical packages. I'm also using 32bit version. A bit slower but less demanding.

I'm publishing this for the future reference. Because i'm sure i'm going to forget how i've installed and configured this OS.

You can download NetBSD 9.2 CD image from this site:

https://www.netbsd.org/releases/formal-9/NetBSD-9.2.html

The VM has this configuration:

1 core cpu
1024mb ram
8gb ide hdd
no soundcard

Instructions

1- Boot your vm from cd image and wait until you see this screen. Press enter and continue next screen.

2- Select your keyboard and press enter.

3- Select install to hard disk and continue.

4- Select yes and continue.

5- Select 8.0G disk.

6- Select "Guid Partition Table"

7- Select correct and continue.

8- Select sizes of NetBSD partitions.

9- Press x to select go on and then press enter.

10- Press x to select go on and then press enter.

11- Select yes and continue.

12- Select BIOS console and continue.

13- Select custom installation and continue.

14- Set "Manual pages" to Yes. (Man pages are always better than google searches)

15- Select "Install selected sets" and continue.

16- Select CD-ROM and continue.

17- Wait for extraction to end.

18- Press enter to start configuration.

19- First thing is to set "root" user password. Select Change root password.

20- Select yes.

21- Enter new root password.

22- Set "Enable raidframe" to No. Because i'm not going to use any RAID implementations. Look here for more info: NetBSD Raidframe

23- Set "Enable cgd" to No. Because im not going to encrypt any disks. Look here for more info: NetBSD cgd

24- Select "Add a user" and press enter.

25- Enter username and add this user to wheel group. (Wheel group means privileged users)

26- Select bin/sh and continue.

27- Set your user password.

28- Select finished configuration and hit enter.

29- Installation is completed. Hit enter.

30- Select reboot the computer and hit enter.

31- After boot, you should be able to see this login screen.

Congratulations

You've successfully installed a minimal NetBSD 32bit operating system.

Creating backups with split and zip in MacOS

Efe Ertugrul — Wed, 25 Nov 2020 09:31:23 +0000

In this post i will show you how to split large files for easy upload and archive in MacOS.

Let's say there are large number of files in your desktop and size difference between these files are too big.
There are 2 Kilobyte files and there are more than 1 Gigabyte files.

Now if you don't have time and you just need to upload these to google drive or dropbox you might need to install their apps to your Mac.

If you don't want to install those apps to your Mac you can use a browser to upload these files but if anything goes wrong with a large file when uploading, you will lose time.

So rather uploading large files you can follow these steps:

1- Put everything in a .zip archive without compressing and encrypt it with a password.
2- Split that one big .zip file to many smaller files.
3- Check their integrity.
4- Upload them to cloud.
5- When you need that .zip file, download splitted files, merge and unzip it with correct password.

Now let's go to our terminal.

Let's say you have a folder named backup_desktop.

Archive backup_desktop/ directory, without compressing and encrypting with a password:

zip -0er backup-desktop.zip backup_desktop/

This command will ask for a password and create a password protected .zip file named backup-desktop.zip.

-0er means:
0: no compression
e: encrypt it with a password
r: means whole directory

Split backup-desktop.zip in backup_split directory with backup-desktop- prefix:

split -b 1m backup-desktop.zip backup_split/backup-desktop-

This will split backup-desktop.zip file and create five files with 1 Megabyte size. (because my backup-desktop.zip is 5 Megabyte)

-b 1m: means split to 1 Megabyte parts.
backup-desktop.zip: means split this file
backup_split/backup-desktop-: means save splitted parts to backup_split directory and save them with "backup-desktop-" prefix

My zip archive is rather small so you might want to change "-b 1m". I usually use "-b 25m" for large files. That creates files with 25 Megabyte sizes each.

My backup_split directory lists like this:

backup-desktop-aa
backup-desktop-ab
backup-desktop-ac
backup-desktop-ad
backup-desktop-ae
backup-desktop-af

All files start with backup-desktop- prefix as we asked.

Now before you use those, you should also check those files' integrity

Use md5 to print checksum of backup-desktop.zip file:

md5 -q backup-desktop.zip

-q: means print only checksum

You will see a text. That is the checksum of backup-desktop.zip file.

Now we have to do the same thing for splitted files.
cat command will put all the splitted files together and md5 will print their put-together checksum:

cat backup_split/backup-desktop-* | md5 -q

cat backup_split/backup-desktop-*: means merge files in backup_split with "backup-desktop-" prefix.
| md5 -q: means send that merged files to md5 -q and md5 -q will print another text which is splitted files' checksum.

Now if those two printed strings are identical that means files are healthy and those splitted files can be merge into backup-desktop.zip.

If two printed strings are not identical that means splitted files cannot merge into backup-desktop.zip.
something is wrong and you should not use those files.

Now you can upload your splitted files to your cloud server.

When you need that backup, download all splitted files into a directory and merge splitted files with this command:

cat backup-desktop-* > backup-desktop.zip

cat backup-desktop-*: means merge every file in directory with backup-desktop- prefix.
> backup-desktop.zip: means save merged files as backup-desktop.zip

This command will create a file named backup-desktop.zip in that directory.

Now you can unzip it with this command:

unzip backup-desktop.zip

It will ask your password for the zip file and if you enter right password, this command will create a directory named backup_desktop and will put all your archived files in it.

Also you can just double-click it. Archive Utility.app can do the same thing.

How to use GnuPG for encrypting files on MacOS

Efe Ertugrul — Sun, 16 Feb 2020 13:23:00 +0000

GnuPG is an implementation of OpenPGP standard.
People use it for public-private key encryption.
It is one of the tools that Edward Snowden used to uncover the secrets of the NSA.

GnuPG is a complex tool.
I will only show you how to use it for file encryption without using keys.
And i will show some configuration files to make commands more simple.

I assume you know how to use a Unix console and have Homebrew package manager installed.

First you should install GnuPG with Homebrew:

brew install gnupg

This will install GnuPG version 2.2.19 (or later)

Check installation:

gpg --version

You should be able to see something like this:

gpg (GnuPG) 2.2.19
libgcrypt 1.8.5
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Now we can use GnuPG.

I have a text file named test.txt.
It contains this text:

this is a test file

To encrypt test.txt file i will use this command:

gpg -c --armor --cipher-algo AES256 --no-symkey-cache --output test.asc test.txt

This command will ask you a password and create an encrypted version of test.txt file and save as test.asc file.

Command explanation:

-c means use symmetric cipher so you will enter a password for that file.
--armor is for a readable ascii output so you can easily copy/paste it.
--cipher-algo AES256 is for using AES-256 cipher. (U.S. government using it so why not)
--no-symkey-cache means GnuPG will not remember password. If you don't enter this --decrypt command won't ask your passphrase.
--output test.asc means save encrypted file as test.asc

Now i have test.asc (encrypted test.txt).
It contains this text:

-----BEGIN PGP MESSAGE-----

jA0ECQMCFBL2lERVNBzj0kwBXxdKtTQSCu4aHyiP93EfUjqYX+Qsp6sWAF+RHUMW
rqjQiLMSlSrxnBxG0E+qfoTmN+26Qb0qd9XAY7S3OTQTfi6XyvjjrNr0yiJ9
=r3J6
-----END PGP MESSAGE-----

As you can see it is readable but meaningless.
This is because of the --armor option we added to the command.

To decrypt test.asc file i will use this command:

gpg --decrypt --no-symkey-cache --output test1.txt test.asc

This command will ask you the password you used and if it is correct it will create a decrypted file as test1.txt.

Now i have test1.txt.
It contains this text:

this is a test file

Configuration Files

There are some configuration files im using.
I will show you how to create these files.
These configuration files are not neccessary but they are shortening the commands i use everyday.

GnuPG creates a folder for itself.
It is normally in your $HOME folder named .gnupg.
It contains caches, your keyrings, your configuration files.
So go there and create a file named gpg.conf.(if it doesn't exists)

Write these in gpg.conf:

armor
personal-cipher-preferences AES256
verbose
use-embedded-filename

Save it.

Now create another configuration file named gpg-agent.conf.(gpg-agent comes with gnupg installation)

Write these in gpg-agent.conf:

default-cache-ttl 0
max-cache-ttl 0
disable-scdaemon

default-cache-ttl 0 and max-cache-ttl 0 disables password cache. disable-scdaemon disables smart card daemon program. Smart Card program starts automatically whenever gpg-agent starts. I don't use smart cards so i'm disabling it.

Save it.

Now actually you should restart your gpg-agent program manually.

Kill it with this command:

gpgconf --kill gpg-agent

It will launch automatically when you call gpg.
If it doesn't you can run this command to launch it:

gpgconf --launch gpg-agent

Anyway now we don't need to add any options. We can simply run our command like this:

gpg -c test.txt

This command will automatically create a file named test.txt.asc with cipher aes-256, also in ascii format and won't remember the password.

To decrypt it simply enter this command:

gpg -d test.txt.asc

It will create a decrypted file as text.txt.

This is one of the many ways to use GnuPG.
As i said before it does so much more.
You can look for more info here at GnuPG

Swift Delegate-Protocol example with SpriteKit

Efe Ertugrul — Mon, 10 Feb 2020 06:43:43 +0000

This is an example of delegation with SpriteKit.
SpriteKit is Apple's 2D Game Framework.
What i will show you is the how/when i use delegation.

I have 3 classes.

1- GameScene

This is the current scene of game. This is where all the object are interacting with each others.

GameScene.swift

import Foundation
import SpriteKit

class GameScene : SKScene
{
    // MARK:- PROPERTIES

    var playerController : PlayerController = PlayerController()

    // MARK:- INIT

    override func didMove(to view: SKView)
    {
        // GameScene loaded
    }

}

Player

This is my player sprite. This object holds all player animations.(move,attack,jump etc.)

Player.swift

import SpriteKit

class Player : SKSpriteNode
{
    func attack() 
    {
        // attack animation here
    }
}

PlayerController

This object is responsible for receiving user inputs and show some animations regarding of those user inputs.

PlayerController.swift

import Foundation

class PlayerController
{
    var player : Player = Player() // create player object

    func attackKeyPressed()
    {
        player.attack() // tell player object to run animation
    }
}

Let's say, user pressed the attack button.
This means PlayerController will call attack animation in Player object.
But now GameScene must know that an attack action happened because Player might hit something with that attack and other objects must change their values according to that action.

This is done by delegation.
To do it change PlayerController object to this:

import Foundation

class PlayerController
{
    var player : Player = Player() // create player object
    weak var delegate : PlayerControllerDelegate? // create delegate object (must be weak otherwise ARC won't deallocates)

    func attackKeyPressed()
    {
        player.attack() // tell player object to attack
        delegate?.playerDidAttack // GameScene will hear this
    }
}

protocol PlayerControllerDelegate: AnyObject // AnyObject for able to weak reference 
{
    func playerDidAttack() // delegate function
}

And change GameScene object to this:

import Foundation
import SpriteKit

class GameScene : SKScene, PlayerControllerDelegate
{
    // MARK:- PROPERTIES

    var playerController : PlayerController = PlayerController()

    // MARK:- INIT

    override func didMove(to view: SKView)
    {
        self.playerController.delegate = self // set delegate
    }

    // MARK:- DELEGATE FUNCTIONS

    func playerDidAttack()
    {
        print("player did attack")
        // do something when player attacks

    }
}

Now whenever an attack input entered by user. PlayerController will run Player object's attack animation and also tell GameScene that an attack happened. Then GameScene can tell other objects what they should do.

You can also download my prototype game Retrokid below.
(Use your keyboard w,a,s,d to walk and attack with k button.)

Retrokid App
Retrokid Source Code (.zip)
Retrokid Source Code (.tar.gz)