I'm currently working on a site for learning MonoGame: https://learn-monogame.github.io/. The front page alone is a collaboration between 3 people. Do you guys know of a good way to give credits for each page? Is that a good idea? I'm currently thinking of adding a section at the bottom of each page with categories like:

• Written by
• Edited by
• Corrections by
• Brainstormed with

With a link to each contributor's preferred social medial. I'm not sure where to look for inspiration for giving credits in a documentation site.

From a reader's point of view, I think it can be nice to get introduced to members of the MonoGame community. Perhaps check out their released games or the ones they are working on.

I'm vaguely in the "market" for a new computer algebra system (Mathematica, Maple, Sage, SymPy, etc etc) and I am curious what experience you all might have with these types of programs. In the past I've used Mathematica, and once you get over the odd aspects of the Language (and hefty license fee), it is a pretty great piece of software. Nonetheless, now that my old student license has expired and I would have to buy a new one (though through my school I can get it at a steep discount) I'm looking at some alternatives. Sage seems particularly appealing since it is open source and apparently well documented, and of course SymPy is powerful although that as stand-alone as these other choices.

There are tons of other options as well, with a wide range of functionality (it really is amazing how much these things can do). My main use cases with these types of things are either: a) algebraic manipulation, b) linear algebra, c) visualization. For these three it does really seem that Mathematica is at the forefront, but I'm all ears for other opinions.

I'm curious, if you have used any or all of these in the past, what were you using them for and what is your opinion?

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Here is my schema:

```sql
CREATE TABLE article_to_warehouse (
  article_id   INTEGER
, warehouse_id INTEGER
)
;
```

How do I add a `UNIQUE` constraint?

I still mainly use Windows, although I've dual-booted Linux a few times and I have Linux Mint on an old laptop right now. One thing I've never understood about Linux is all the different distributions - their different reputations and why they have them. What is the mechanical difference between using one distribution of Linux and another? Or are the differences usually not mechanical?

For example, Ubuntu and Debian seem to be large families, meaning that a lot of other distributions are based on them (using packages built for them in their package managers at least) as well as being popular distros on their own. But what's different between the two of them, and between each and the other distros based on them? (and what's similar? I gather they all use the Linux kernel at least!)

I also know that people are quite opinionated on their choice of distro, I wondered what reasons people had for their choice. What things are easier or harder for you in your distro of choice? Is it mainly day-to-day tasks that are important or more how the OS works underneath? How much difference does your preferred distro make?

For myself, I've only used Kubuntu (though not much) and Linux Mint, which was mainly for UI reasons, and particularly for the latter, ease of use for someone used to Windows (at least that was what I found years ago when I first looked into it).

Though I doubt I'll ever fully move away from Windows I would like / need to have access to a Linux OS, so maybe this will help me to know what is important to look for. But I also hope it'll be a useful and interesting discussion topic. Also, there are some previous discussions on the latter question so I'd be more interested in learning about the main topic.

also, please do add more tags

Via email:

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I've got a crappy Chromebook running GalliumOS (Xubuntu) and Chromium is slow as molasses. I tried a few other browsers like Otter and Falkon. They're alright for most sites -- not Tildes, but this seems consistent with QT5 browsers.

Anyway, outside of text browsers, anybody have any light weight browser suggestions?

This is a recurring post to discuss programming or other technical projects that we've been working on. Tell us about one of your recent projects, either at work or personal projects. What's interesting about it? Are you having trouble with anything?

General Programming Q&A thread! Ask any questions about programming, answer the questions of other users, or post suggestions for future threads.

Don't forget to format your code using the triple backticks or tildes:

Here is my schema:

```sql
CREATE TABLE article_to_warehouse (
  article_id   INTEGER
, warehouse_id INTEGER
)
;
```

How do I add a `UNIQUE` constraint?

This is a recurring post to discuss programming or other technical projects that we've been working on. Tell us about one of your recent projects, either at work or personal projects. What's interesting about it? Are you having trouble with anything?

My Linux desktop is having a bit of difficulty with bad sectors. Lately I've had to boot into recovery and run an fsck a few times to try to fix a problem where the OS drops into read-only mode at the drop of a hat. Today I tried copying some files from one directory to another and got the following error message:
cp: error reading "foo/bar": Input/output error

I've just booted into a live USB and run fsck /dev/sda1 -c and it fixed a load of bad sectors, but the above error message is still happening.

A bit of googling tells me that this is down to bad sectors on the SSD, and I'm not really sure what that means. Is anybody able to enlighten me? And as a follow-up question, would reformatting the hard drive resolve the problem, or are there any other things I can try to fix it?

Since I took so long to reply to Tips to use NixOS on a server? by @simao, I decided to create a new topic to share my configs. Hopefully this is informative for anyone looking to do similar things - I'll also gladly take critiques, since my setup is probably not perfect.

First, I will share the output of 'lsblk' on my VPS:

NAME      MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
vda       253:0    0   180G  0 disk  
├─vda1    253:1    0   512M  0 part  /boot
└─vda2    253:2    0 179.5G  0 part  
  └─crypt 254:0    0 179.5G  0 crypt 

That is, I use an unencrypted /boot partition, vda1, with GRUB 2 to prompt for a passphrase during boot, to unlock the LUKS encrypted vda2. I prefer to use ZFS as my file system for the encrypted drive, and LUKS rather than ZFS encryption. This is an MBR drive, since that's what my VPS provider uses, though UEFI would look the same. The particular way I do this also requires access through the provider's tools, and not ssh or similar. The hardware-configuration.nix file reflects this:

# Do not modify this file!  It was generated by ‘nixos-generate-config’
# and may be overwritten by future invocations.  Please make changes
# to /etc/nixos/configuration.nix instead.
{ config, lib, pkgs, modulesPath, ... }:

{
  imports =
    [ (modulesPath + "/profiles/qemu-guest.nix")
    ];

  boot.initrd.availableKernelModules = [ "aes_x86_64" "ata_piix" "cryptd" "uhci_hcd" "virtio_pci" "sr_mod" "virtio_blk" ];
  boot.initrd.kernelModules = [ ];
  boot.kernelModules = [ ];
  boot.extraModulePackages = [ ];

  fileSystems."/" =
    { device = "rpool/root/nixos";
      fsType = "zfs";
    };

  fileSystems."/home" =
    { device = "rpool/home";
      fsType = "zfs";
    };

  fileSystems."/boot" =
    { device = "/dev/disk/by-uuid/294de4f1-72e2-4377-b565-b3d4eaaa37b6";
      fsType = "ext4";
    };

  swapDevices = [ ];

}

# Edit this configuration file to define what should be installed on
# your system.  Help is available in the configuration.nix(5) man page
# and in the NixOS manual (accessible by running ‘nixos-help’).

{ config, lib, pkgs, ... }:

{
  imports =
    [ # Include the results of the hardware scan.
      ./hardware-configuration.nix
    ];

  # Hardware stuff
  # add the following to hardware-configuration.nix - speeds up encryption
  #boot.initrd.availableKernelModules ++ [ "aes_x86_64" "cryptd" ];
  boot.initrd.luks.devices.crypt = {
    # Change this if moving to another machine!
    device = "/dev/disk/by-uuid/86090289-1c1f-4935-abce-a1aeee1b6125";
  };
  boot.kernelParams = [ "zfs.zfs_arc_max=536870912" ]; # sets zfs arc cache max target in bytes
  boot.supportedFilesystems = [ "zfs" ];
  nix.maxJobs = lib.mkDefault 6; # number of cpu cores

  # Use the GRUB 2 boot loader.
  boot.loader.grub.enable = true;
  boot.loader.grub.version = 2;
  # boot.loader.grub.efiSupport = true;
  # boot.loader.grub.efiInstallAsRemovable = true;
  # boot.loader.efi.efiSysMountPoint = "/boot/efi";
  # Define on which hard drive you want to install Grub.
  boot.loader.grub.device = "/dev/vda"; # or "nodev" for efi only
  boot.loader.grub.enableCryptodisk = true;
  boot.loader.grub.zfsSupport = true;

  networking.hostName = "m"; # Define your hostname.
  # networking.wireless.enable = true;  # Enables wireless support via wpa_supplicant.

  # The global useDHCP flag is deprecated, therefore explicitly set to false here.
  # Per-interface useDHCP will be mandatory in the future, so this generated config
  # replicates the default behaviour.
  networking.useDHCP = false;
  networking.interfaces.ens3.useDHCP = true;
  networking.hostId = "aoeu"; # set this to the first eight characters of /etc/machine-id for zfs
  networking.nat = {
    enable = true;
    externalInterface = "ens3"; # this may not be the interface name
    internalInterfaces = [ "wg0" ];
  };
  networking.firewall = {
    enable = true;
    allowedTCPPorts = [ 53 25565 ]; # open 53 for DNS and 25565 for Minecraft
    allowedUDPPorts = [ 53 51820 ]; # open 53 for DNS and 51820 for Wireguard - change the Wireguard port
  };
  networking.wg-quick.interfaces = {
    wg0 = {
      address = [ "10.0.0.1/24" "fdc9:281f:04d7:9ee9::1/64" ];
      listenPort = 51820;
      privateKeyFile = "/root/wireguard-keys/privatekey"; # fill this file with the server's private key and make it so only root has read/write access

      postUp = ''
        ${pkgs.iptables}/bin/iptables -A FORWARD -i wg0 -j ACCEPT
        ${pkgs.iptables}/bin/iptables -t nat -A POSTROUTING -s 10.0.0.1/24 -o ens3 -j MASQUERADE
        ${pkgs.iptables}/bin/ip6tables -A FORWARD -i wg0 -j ACCEPT
        ${pkgs.iptables}/bin/ip6tables -t nat -A POSTROUTING -s fdc9:281f:04d7:9ee9::1/64 -o ens3 -j MASQUERADE
      '';

      preDown = ''
        ${pkgs.iptables}/bin/iptables -D FORWARD -i wg0 -j ACCEPT
        ${pkgs.iptables}/bin/iptables -t nat -D POSTROUTING -s 10.0.0.1/24 -o ens3 -j MASQUERADE
        ${pkgs.iptables}/bin/ip6tables -D FORWARD -i wg0 -j ACCEPT
        ${pkgs.iptables}/bin/ip6tables -t nat -D POSTROUTING -s fdc9:281f:04d7:9ee9::1/64 -o ens3 -j MASQUERADE
      '';

      peers = [
        { # peer0
          publicKey = "{client public key}"; # replace this with the client's public key
          presharedKeyFile = "/root/wireguard-keys/preshared_from_peer0_key"; # fill this file with the preshared key and make it so only root has read/write access
          allowedIPs = [ "10.0.0.2/32" "fdc9:281f:04d7:9ee9::2/128" ];
        }
      ];
    };
  };

  # Configure network proxy if necessary
  # networking.proxy.default = "http://user:password@proxy:port/";
  # networking.proxy.noProxy = "127.0.0.1,localhost,internal.domain";

  nixpkgs.config = {
    allowUnfree = true; # don't set this if you want to ensure only free software
  };

  # Select internationalisation properties.
  i18n.defaultLocale = "en_US.UTF-8";
  console = {
    font = "Lat2-Terminus16";
    keyMap = "us";
  };

  # Set your time zone.
  time.timeZone = "America/New_York"; # set this to the same timezone your server is located in

  # List packages installed in system profile. To search, run:
  # $ nix search wget
  environment = {
    systemPackages = with pkgs; let
      nvimcust = neovim.override { # lazy minimal neovim config
        viAlias = true;
        vimAlias = true;
        withPython = true;
        configure = {
          packages.myPlugins = with pkgs.vimPlugins; {
            start = [ deoplete-nvim ];
            opt = [];
          };
          customRC = ''
            if filereadable($HOME . "/.config/nvim/init.vim")
              source ~/.config/nvim/init.vim
            endif

            set number

            set expandtab

            filetype plugin on
            syntax on

            let g:deoplete#enable_at_startup = 1
          '';
        };
      };
    in
    [
      jdk8
      nvimcust
      p7zip
      wget
      wireguard
    ];
  };

  # Some programs need SUID wrappers, can be configured further or are
  # started in user sessions.
  # programs.mtr.enable = true;
  # programs.gnupg.agent = {
  #   enable = true;
  #   enableSSHSupport = true;
  #   pinentryFlavor = "gnome3";
  # };

  # List services that you want to enable:

  # Enable the OpenSSH daemon.
  services = {
    dnsmasq = {
      enable = true;
      # this allows DNS requests from wg0 to be forwarded to the DNS server on this machine
      extraConfig = ''
        interface=wg0
      '';
    };
    fail2ban = {
      enable = true;
    };
    openssh = {
      enable = true;
      permitRootLogin = "no";
    };
    zfs = {
      autoScrub = {
        enable = true;
        interval = "monthly";
      };
    };
  };

  # Set sudo to request root password for all users
  # this should be changed for a multi-user server
  security.sudo.extraConfig = ''
    Defaults rootpw
  '';

  # Define a user account. Don't forget to set a password with ‘passwd’.
  users.users = {
    vpsadmin = { # admin account that has a password
      isNormalUser = true;
      home = "/home/vpsadmin";
      extraGroups = [ "wheel" ]; # Enable ‘sudo’ for the user.
      shell = pkgs.zsh;
    };
    mcserver = { # passwordless user to run a service - in this instance minecraft
      isNormalUser = true;
      home = "/home/mcserver";
      extraGroups = [];
      shell = pkgs.zsh;
    };
  };

  systemd = {
    services = {
      mcserverrun = { # this service runs a systemd sandboxed modded minecraft server as user mcserver
        enable = true;
        description = "Start and keep minecraft server running";
        wants = [ "network.target" ];
        after = [ "network.target" ];
        serviceConfig = {
          User = "mcserver";
          NoNewPrivileges = true;
          PrivateTmp = true;
          ProtectSystem = "strict";
          PrivateDevices = true;
          ReadWritePaths = "/home/mcserver/Eternal_current";
          WorkingDirectory = "/home/mcserver/Eternal_current";
          ExecStart = "${pkgs.jdk8}/bin/java -Xms11520M -Xmx11520M -server -XX:+AggressiveOpts -XX:ParallelGCThreads=3 -XX:+UseConcMarkSweepGC -XX:+UnlockExperimentalVMOptions -XX:+UseParNewGC -XX:+ExplicitGCInvokesConcurrent -XX:MaxGCPauseMillis=10 -XX:GCPauseIntervalMillis=50 -XX:+UseFastAccessorMethods -XX:+OptimizeStringConcat -XX:NewSize=84m -XX:+UseAdaptiveGCBoundary -XX:NewRatio=3 -jar forge-1.12.2-14.23.5.2847-universal.jar nogui";
          Restart = "always";
          RestartSec = 12;
        };
        wantedBy = [ "multi-user.target" ];
      };
      mcserverscheduledrestart = { # this service restarts the minecraft server on a schedule
        enable = true;
        description = "restart mcserverrun service";
        serviceConfig = {
          Type = "oneshot";
          ExecStart = "${pkgs.systemd}/bin/systemctl try-restart mcserverrun.service";
        };
      };
    };
    timers = {
      mcserverscheduledrestart = { # this timer triggers the service of the same name
        enable = true;
        description = "restart mcserverrun service daily";
        timerConfig = {
          OnCalendar = "*-*-* 6:00:00";
        };
        wantedBy = [ "timers.target" ];
      };
    };
  };

  # This value determines the NixOS release from which the default
  # settings for stateful data, like file locations and database versions
  # on your system were taken. It‘s perfectly fine and recommended to leave
  # this value at the release version of the first install of this system.
  # Before changing this value read the documentation for this option
  # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
  system.stateVersion = "20.09"; # Did you read the comment?

}

Edit: Also, the provider I use is ExtraVM, who has been excellent.

Hey guys,

I have been flip-flopping back and forth on this idea for a while, and would love some feedback on whether peeps would find this valuable.

Although I still call my self a "software developer" (and try to code daily), for the last 8 years I have ran a small 5-person agency that I started from the ground up, so my role was really CEO/CTO/CFO/Everything-O. My company focused on delivering high-quality custom software. Not brochure websites, and not Wordpress - our niche was internal business software (or as I like to call it "boring software for boring businesses") - and for a client service company we got very high margins of return.

Last year my business was acquired by a larger company which was an amazing result after the time and effort I had poured into it. I have realised I now want to help other developers who want to start their own software agency, or maybe they already have and are looking for hints or advice on certain topics.

So I have started Dev to Agency - a part blog part guidebook for how a full-stack developer can start and successfully run a software development agency, the things to pay attention too (and the things to ignore), and the key-values that I feel helped my business go from nothing, to 7 figures per year, and then to being acquired (if that is a path people would want to take).

I have just published my first couple of posts, About Dev To Agency that is a rundown of what I hope to achieve with this, then a post about My small custom software development agency - which gives an overview of what I built and where I think my articles will add value, and lastly You are the gold standard which covers how I feel an owner/maker should set the businesses standards and practises based of their personal values.

I have never written a blog before (or really done any writing before), so it would be fantastic to get some feedback from the community, and if there are any developers that this could interest then please subscribe on the website.

Cheers,

Chris.

This is a recurring post to discuss programming or other technical projects that we've been working on. Tell us about one of your recent projects, either at work or personal projects. What's interesting about it? Are you having trouble with anything?

General Programming Q&A thread! Ask any questions about programming, answer the questions of other users, or post suggestions for future threads.

Don't forget to format your code using the triple backticks or tildes:

Here is my schema:

```sql
CREATE TABLE article_to_warehouse (
  article_id   INTEGER
, warehouse_id INTEGER
)
;
```

How do I add a `UNIQUE` constraint?