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#!/usr/bin/env bash

# Installs NixOS on an OVH server, wiping the server.
#
# This is for a specific server configuration; adjust where needed.
# Originally written for an OVH STOR-1 server.
#
# Prerequisites:
#   * Create a LUKS key file at /root/benacofs-luks-key
#     e.g. by copying it up.

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

with lib;

let
  cfg = config.services.ceph-benaco;

  inherit (pkgs.callPackage ../helpers.nix {}) ensureUnitExists;
in

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How to determine if the nix sandbox is in effect on a system

Do the same as the nix-info script, which nix-builds this file and inspects the exit code.

Short version:

nix-build --no-out-link -E 'import <nixpkgs/pkgs/tools/nix/info/multiuser.nix>' 2> /dev/null

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# Build with:
#     NIX_PATH=nixpkgs=$HOME/src/nixpkgs nix-build --no-link '<nixpkgs/nixos>' -A config.system.build.tarball -I nixos-config=thisfile.nix
# You can also use
#     -A config.system.build.toplevel
# to build something you can browse locally (that uses symlinks into your nix store).

{config, pkgs, ...}:
{
  # We need no bootloader, because the Chromebook can't use that anyway.
  boot.loader.grub.enable = false;

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-- Creates the table recording the current migration.

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

BEGIN;

-- Note: `create or replace function` cannot be run concurrently; postgres
--       will error with "tuple concurrently updated" when that happens.
--       That's why we wrap it in a transaction-level exclusive advisory lock.
--       See http://stackoverflow.com/questions/40525684/tuple-concurrently-updated-when-creating-functions-in-postgresql-pl-pgsql/44101303

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I believe the following is the best way to work with Nagle's algorithm / TCP_NODELAY / TCP_CORK.

It is described in this RedHat manual and the verdict is:

• Set TCP_NODELAY = 1, always.
• If you can batch data for sending by creating a buffer manually, or using writev(), prefer that.
• If you cannot (e.g. "when using different libraries that provides abstractions for layers" from the above manual):
  • Set TCP_CORK = 1, then write the data, then set TCP_CORK = 0.
• This builds a packet in kernel space and then flushes it out.

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{-# LANGUAGE ScopedTypeVariables, BangPatterns #-}

-- Example of how forM_ [1..N] is slow

module Main (main) where

import Prelude hiding (read)
import Control.Monad
import Data.Vector ((!), Vector)
import qualified Data.Vector as V

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GlusterFS SSL setup tutorial

Following:

• http://gluster.readthedocs.io/en/latest/Administrator%20Guide/SSL/
• https://access.redhat.com/documentation/en-US/Red_Hat_Storage/3.1/html/Administration_Guide/chap-Network_Encryption.html

I use GlusterFS 3.9 here.

Prerequisites

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import numpy as np
import numpy.linalg

# Relevant links:
#   - http://stackoverflow.com/a/32244818/263061 (solution with scale)
#   - "Least-Squares Rigid Motion Using SVD" (no scale but easy proofs and explains how weights could be added)


# Rigidly (+scale) aligns two point clouds with know point-to-point correspondences
# with least-squares error.

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# This `firefox-vm.nix` builds a simple NixOS VM with XFCE and Firefox inside.
#
# Build and run it with:
#
#     nix-build '<nixpkgs/nixos>' -A vm -I nixos-config=./firefox-vm.nix
#     result/bin/run-nixos-vm
#
# Log in as "root" with empty password.
#
# To delete the VM state (storage):