hed0rah jrelo

Linux simple performance tweaks

Change the I/O Scheduler

Open $ vim /etc/default/grub then add elevator=noop next to GRUB_CMDLINE_LINUX_DEFAULT. Run $ update-grub and $ cat /sys/block/sda/queue/scheduler to be sure that noop is being used:

$ vim /etc/default/grub
$ update-grub
$ cat /sys/block/sda/queue/scheduler

[noop] deadline cfq

http://brainwreckedtech.wordpress.com/2012/01/08/howto-convert-vdis-between-fixed-sized-and-dynamic-in-virtualbox/ http://www.webdesignblog.asia/software/linux-software/resize-virtualbox-disk-image-manipulate-vdi/#comment-474

While there is no way to actually switch a VDI between fixed-size and dynamic, you can clone the existing VDI into a new one with different settings with VBoxManage.

VBoxManage clonehd [old-VDI] [new-VDI] --variant Standard
VBoxManage clonehd [old-VDI] [new-VDI] --variant Fixed

If you want to expand the capacity of a VDI, you can do so with

Links

Finding

$ grep -rnw 'directory' -e "pattern"

-r is recursive, -n is line number and -w stands match the whole word. Along with these, --exclude or --include parameter could be used for efficient searching. Something like below:

$ grep --include={*.c,*.h} -rnw 'directory' -e "pattern"

This will only search through the files which have .c or .h extensions. Similarly a sample use of --exclude:

	#!/usr/bin/env perl
	use strict;
	use warnings;
	use PerlIO::gzip;

	my $pattern = $ARGV[0];
	my $file = $ARGV[1];
	open my $z, '<:gzip', $file or die "gunzip failed: $!\n";
	while ( <$z> ) {
	print if /$pattern/i;

	// XORCipher - Super simple encryption using XOR and Base64
	//
	// Depends on [Underscore](http://underscorejs.org/).
	//
	// As a warning, this is not a secure encryption algorythm. It uses a very
	// simplistic keystore and will be easy to crack.
	//
	// The Base64 algorythm is a modification of the one used in phpjs.org
	// * http://phpjs.org/functions/base64_encode/
	// * http://phpjs.org/functions/base64_decode/

	#!/bin/sh
	#
	# Use posixregex CLI tool from: https://github.com/syzdek/dmstools/blob/master/src/posixregex.c

	RE_IPV4="((25[0-5]\|(2[0-4]\|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]\|(2[0-4]\|1{0,1}[0-9]){0,1}[0-9])"

	posixregex -r "^(${RE_IPV4})$" \
	127.0.0.1 \
	10.0.0.1 \
	192.168.1.1 \

	/* Doubly Linked List implementation */
	#include<stdio.h>
	#include<stdlib.h>

	struct Node {
	int data;
	struct Node* next;
	struct Node* prev;
	};

	TARGET = test

	CC = gcc

	CFLAGS = -c -v

	VPATH = src
	SRC = test.c
	OBJ = $(SRC:.c=.o)

	#Install necessary things
	apt-get update
	apt-get install kernel-package libncurses5-dev fakeroot wget bzip2 build-essential -y

	#Get the kernel
	cd /usr/src
	wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.13.tar.xz
	wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.13.tar.sign
	gpg --verify linux-3.13.tar.sign
	tar xpvf linux-3.13.tar.xz