TheHackersManual2015RevisedEdition

Hard disks have increased in size beyond what the MS-DOS partitioning scheme can handle. It can’t address disks larger than 2TiB because the partition tables store sector addresses as 32-bit numbers, and this means that there can’t be more than 2^32 sectors. Because

each sector contains 512 bytes, this gives a

therefore limited to 512 bytes – 446 bytes for the bootloader, and a partition table containing up to four 16-byte records. The last two bytes contain a signature that the BIOS uses to recognise a valid MBR. The partition tables use 32-bit sector address fields, which means they can’t address disks larger than 2TiB. This type of partition table is often referred to as an MS-DOS partition table in an attempt to differentiate it from the new GPT.

The problems with this configuration include being limited to one bootloader, the limitation of four partitions and the maximum 2TiB disk size. The UEFI supports multiple bootloaders, and the GPT supports up to 128 partitions and works with disks bigger than 2TiB. The other thing that UEFI brings to the table is the ability to secure the boot process.

Because the BIOS expects the bootloader to be located in the first sector of the disk, there

can only be one per disk. Most BIOSes allow selection of the boot disk and, therefore, can support as many bootloaders as there are physical disks. In contrast, UEFI ignores any bootloader in sector 0, but instead allows multiple bootloaders to exist on a single disk by using a special partition instead of an absolute sector. The special partition is known as the EFI System Partition, or ESP, and is formatted with a FAT filesystem (usually FAT32) and typically sized between 100MiB and 250MiB. The UEFI specification requires it to be the first partition and it must have its boot flag set. On a Linux system it’s customary to mount the ESP under /boot/efi. By convention, bootloaders are stored on the ESP in vendor-specific subdirectories, and the UEFI forum has a list of these sub-directories at www.uefi.org/specs/ esp_registry.

At the core of UEFI is its firmware, and it is responsible for loading and executing UEFI applications. These are standalone programs that depend only on the firmware’s services – they do not need an operating system. They can be pre-boot maintenance/diagnostic tools, but most are operating system bootloaders. The UEFI firmware contains a boot manager

maximum size of 2TiB. The new GPT partitioning scheme overcomes this limitation by using 64-bit fields, and these allow storage of 2^64 512-byte sectors, or 8ZiB (9.4ZB).

That is more than all the storage currently existing in the world. (http://tinyurl.com/dxvramm).

that enables the user to launch UEFI applications. A boot manager is similar to a bootloader, like Grub, except that it can only load EFI applications. It is possible to configure the Linux kernel (since 3.3) as an EFI application, and doing so can remove the need for a bootloader such as Grub because UEFI is then able to boot it directly.

The UEFI firmware can read partition tables and FAT filesystems, unlike the BIOS which relies on a bootloader. It is configurable via EFI variables that are stored in NVRAM. The main variable driving the EFI boot manager is called BootOrder and defines the menu items it displays. If it isn’t set, the firmware follows a standard procedure to locate a bootloader at a specific path on the ESP. The path, which is architecture-dependent, is of the form:

\EFI\BOOT\BOOT[architecture name].EFI

The G in GPT stands for GUID, which is a Globally Unique Identifier, an implementation of the Universally Unique Identifier standard defined by RFC4122. The GPT uses GUIDs to identify disks and partitions. It begins at sector 1 with a

header that defines the number and size of the partition records in the table that follows. The header contains a disk GUID that uniquely identifies the disk, and each partition defined in the GPT contains two GUIDs: the first represents the partition’s type and the second uniquely identifies it. The header also contains a CRC32 checksum that can be used by the firmware or operating system to verify data integrity. Don’t go manually editing your partition table!

The GPT can hold 128 partitions, and this removes the need for logical and extended partitions. The extended partition was a way to overcome the four-partition limit of the MBR. It allowed one of those partitions to be used as an extended partition that could be sub-divided into many logical partitions.

Each partition record is 128 bytes long and contains the GUIDs mentioned, the partition’s beginning and end sector addresses, some attributes and a human-readable name.

A second copy of the GPT is stored at the end of the disk as a backup. To accommodate 128 such partition records requires 16,384 bytes. This is 32 sectors, which means that the first usable sector on a GPT disk is sector 34.

A GPT disk contains two copies of its partition table, plus a protective MS-DOS partition table.

The GPT scheme also includes a master boot record, and its purpose is to help prevent corruption of a GPT disk by tools that are not GPT-aware. This Protective MBR, or PMBR, contains an MS-DOS partition table with one partition covering the whole disk (or 2TiB if the disk is bigger). This partition is marked with a type of 0xEE. Systems unaware of GPT will see an unknown partition occupying the whole disk and leaving no available space.

Another use of the protective MBR is to allow a BIOS to boot a GPT disk. If it contains a bootloader, the BIOS will blindly load and execute it. If that bootloader understands GPT, it can boot it. One such bootloader is Grub2, and is used by many Linux distributions. This allows BIOS-based systems to use disks greater than 2TiB.

MS-DOS partitioned disks usually leave a gap (known as the DOS Compatibility region), starting at sector 1 and running up to the beginning of the first partition. Bootloaders traditionally used this unallocated space to locate code (Grub 1 wrote its stage 1.5 loader here). With GPT, the partition table begins at sector 1, immediately after the PMBR – so there is no unallocated space to use in this way. Instead, the GPT specification provides for a special BIOS boot partition for use by boot loaders that would otherwise have used the DOS Compatibility region. Grub 2 writes

its bootloader directly on to that partition (it does not contain a filesystem). Given that the presence of the DOS Compatibility region was by convention rather than definition, having a specifically allocated partition is more robust.

So far,we’ve presented a lot of theory.We’ll now put that into practice to set up a new system based on UEFI and GPT.Our new system will dual boot: it will work with both UEFI and BIOS firmware.

The UEFI shell

One special UEFI application is the UEFI shell. It’s a basic command-line environment that you can use to launch EFI applications or do basic configuration and troubleshooting.

The firmware will drop you into the shell if there is no suitably-configured start-up sequence in place. The other way to get there is via the firmware’s menu interface in response to a special key. In VirtualBox it’s the [Del] key, but you will need to have quick reflexes! You can also hit c at the Grub menu to access the Grub prompt and then type exit. Two handy shell commands are help and bcfg:

> bcfg boot dump -v

will list the EFI applications listed in the boot manager. You can add/remove options or change their ordering. To add a boot option:

>bcfg boot add 3 fs0:\EFI\arch_grub\grubx64.efi “ArchLinux Grub”

and to move it up the list:

>bcfg boot mv 3 2

One last shell command worth remembering is reset, which resets the machine to start the

Buying a modern motherboard means that you don’t have to worry about buying certain other components. In the past, we might have recommended purchasing a sound card, but pretty much any motherboard you buy these days comes with a perfectly good built-in audio solution. The exact same can be said for Ethernet network adaptors – you no longer need to buy a discrete network card for day-to-day computing, because your motherboard will come with one already. This means that you’re not going to need to cough up the cash to buy those extra components.

What processor?

So what do you need to buy? The first consideration is what processor to go for, as this will determine which motherboards you’ll be able to use due to the socket type it’ll use. As an aside all desktop processors are 64-bit these days (Intel Atom and older Intel Celeron processors are an exception) and you’ll need it as we’re going to suggest at least 4GB of memory. None of this is a problem as all distros also offer 64-bit builds.

So bearing in mind that you want a medium-powered PC for day-to-day tasks, we’d recommend going for an Intel Core i5-4570. This is a very capable processor that comes in at a pretty low cost (it’s available for around £140), thanks to the lack of more advanced features that Intel’s more expensive processors come equipped with. For example, the CPU multiplier of the Intel Core i5-4570 is locked, but because you’re not looking to overclock this processor to eke out every ounce of power, this won’t be a problem. Unlike the higher end Intel chips, it has four threads, rather than eight, and it does not support Hyper-threading. It is therefore not the best chip for professional video editing and 3D rendering – but you’re unlikely to need a standard desktop PC for such tasks. It is more than powerful enough for most undertakings, and the onboard graphics (Intel HD Graphics 4600) is absolutely fine for media, photo editing and even the odd game.

If you’re looking for a bit more grunt, and you have the budget for it, then the Intel Core i7-4770K is another excellent processor, though quite a bit more expensive at around £242. On the other hand, if you are trying to save some money, then the Intel Core i3-4130 is a good choice at £83. Interestingly, it actually has a higher clockspeed than the Intel Core i5-4570 (3.4Ghz compared to 3.2GHz), but it is only dual-core, whereas the i5 is quad-core. All of these processors use the LGA 1150 socket – more on that in a bit – which will make choosing a motherboard much easier.

You may have noticed that this section of the article has been a bit Intel-heavy; if you’d rather have an AMD-flavoured processor, then the A10-7850K is a great alternative. It has onboard AMD Radeon R7 graphics and costs around £135, which is a little less than the i5-4570. If you want this processor, you will need to find a motherboard that supports the FM2+ socket. All of the processors listed here should come complete with a heat sink and fan. While they won’t be much good if you’re a hardcore gamer or a keen overclocker, they will be absolutely fine for a regular desktop computer

user and you won’t have to worry about buying an additional fan or heat sink, either.

The mother

Now you’ve settled on a processor, you can start thinking about the motherboard. The motherboard will determine quite a few important aspects of the PC you’re building, such as the size of the case and the amount of RAM that it can hold. If you’ve gone for one of the Intel processors we suggested, then you need to make sure the motherboard supports an Intel chipset and the LGA 1150 socket. For a standard desktop build we’d recommend the ASUS H81M-C motherboard. This might be a budget board but it offers everything you’ll need. With this board you get two DIMM slots for DDR3 RAM (up to a reasonable 16GB), built-in audio, four USB 3.0 ports, two USB 2.0 ports, a built-in network card, and HDMI, VGA and DVI ports for connecting monitors. Basically, pretty much everything you need. It comes with six SATA 3 ports, so you can add in plenty of hard drives. They are backwards compatible with older SATA drives, so if you have some old hard drives lying around you can still use them

– though if they have IDE connectors you’ll have to use an adaptor. If you need a new hard drive, then we’d recommend

the Western Digital 1TB drive. The capacity is adequate and has the standard disk speed of 7,200rpm. While solid state drives offer a bigger speed boost, their relatively limited capacity mean they aren’t really a worthwhile purchase for day-to-day computing.

You’ll also need a PSU (power supply unit) to power the components and the computer itself. We’ve selected components with relatively low power consumption, and as we’re not using a discrete graphics card, you’re not going to need a monster 1,000W power supply. However, if you want to expand your PC later on, it’s a good idea to buy a PSU with additional watts to what you’ll need. It’s also well worth going for a PSU that is dependable – you don’t want it breaking down or damaging your components – and with good power efficiency, as this PC will be getting lots of use. Don’t just buy the cheapest model available, and make sure you read customer reviews, which are a good indicator of the reliability of a PSU. For power efficiency, get a PSU that has an 80 Plus certificate. This means the PSU will only waste 20% or less of its energy as heat, reducing bills and noise levels.

You’ll want to make sure the PSU has the right type of connectors for your motherboard. All new PSUs have been ATX12V v2.31 compliant since around 2008 and if you opt for a system with modular cabling it’ll ensure it can adapt to your needs, though this tends to only be available on higher-end models. We’re recommending the Corsair CX500, which combines reliability, power and efficiency for around £46. For the case, you don’t need anything flashy. Any standard ATX case is going to do the job and can cost as little as £15, just don’t get one that includes a PSU.

Only a few short years ago the idea of building a gaming PC filled to the brim with the latest components and then installing Linux on it would

have you burnt at the stake as a witch, or at the very least garnered you some disapproving head shakes from your gaming pals. These days an increasing number of high profile blockbuster games and indie titles are coming to Linux, encouraged by Valve – the games developer and company behind Steam, the digital distribution service – which has created its own Linux distro, SteamOS.

With companies like Crytek (Crysis and Far Cry series) and Epic (Gears of War and Unreal series) that both produce the high-end game engines that power many of the bigger releases – as well as developing graphically impressive games themselves – fully embracing Linux, gaming has never been in ruder health.

There are a number of reasons why you’d want to build a Linux gaming powerhouse. For a start, Linux is free, so you can put the money you would have spent on a Windows licence towards a more powerful graphics card – always a

The mighty Nvidia Titan is an exercise in pure 3D graphics performance.

popular option with gamers. Because Linux distros take up a lot less resources when running in the background compared to Windows, it also means that you’ll see much better results running a game in Linux.

So what do you need to take into account when building a Linux gaming machine? The mindset behind creating a gaming PC that can tackle all of the latest games at the best possible quality is quite different to when you’re building a standard desktop machine. You want the most power you can get for your money, and if you want to try your hand at overclocking, you’re going to want components that let you squeeze out every last drop of power. This means that you’re going to be looking at spending quite a bit more, and sometimes overlooking cheaper components for more expensive ones.

Planning your machine

Having said that, the base of our gaming machine is some what different to that of the desktop PC. The ASRock H97M Pro4 motherboard is an excellent choice, thanks to its excellent price and support for some of the latest technology. In our benchmarks it also performed incredibly well for memory bandwidth and overclocking performance. The Intel Core i5-4570 processor we suggested on the previous pages is also a perfectly fine choice, though it does not support overclocking. This will be fine for most people, but if you want some additional leeway in getting the most performance for your money, then the Intel Core i5-4670K offers not just a faster base clockspeed (3.4GHz compared to 3.2GHz), but it’s also able to be overclocked to around 4.5GHz – offering a pretty decent boost in performance for free. Although the Intel Core i5-4670K comes with a fan for keeping it cool, unlike the desktop PC, this won’t be enough. The processor is going to be getting a lot hotter during use, because of the intensive nature of games and especially if it is getting overclocked, which means we’ll need a different cooler to

Performance parts

If you want the best performance out of your gaming PC, then you’re going to want to splash out on the fastest kit you can afford. When it comes to RAM, it’s less about the amount (8GB is still more than enough for gaming), but more about the frequency and latency of the RAM. If you decide to use the suggested ASRock H97M Pro4 motherboard, it supports dual channel DDR3 RAM with four slots, so we’ll want a set of RAM that comes in either two or four sticks (eg. two sticks of 4GB).

The frequency of RAM can be between 800MHz to 3,000MHz, with our motherboard supporting an overclocked frequency of 2,933. For gaming purposes, we don’t need much over 1,600MHz. The faster the RAM, the more latency occurs, so this is a good trade off. Faster RAM

also produces more heat, which in turn requires RAM sticks to include large heatsinks. These can end up causing problems if you have a large CPU cooler, as you may find it doesn’t fit. The HyperX Fury memory ticks all these boxes, and comes at a decent price at around £54.

The most important part of a gaming machine is the graphics card, and the most expensive – however it may be worth paying more to keep your PC relevant for the near future. The most powerful single card graphics card on the market today is the Zotac GeForce GTX 970, which has a huge 4GB of GDDR5 memory with a 384-bit interface and bandwidth of 3,36GB/sec. This is a card that’s going to be futureproof for a long time, and is the one to get if you want the ultimate graphics card. It comes at a price,

however, at just under £500. This will be beyond most people’s budgets, and certain aspects of the card, such as the 4GB of GDDR5, will not be fully exploited by even the most demanding games, especially if you’re only going to be running one monitor. When 4K displays become the norm, however, that GDDR5 will be vital.

For a more realistic budget we’d recommend going for the AMD Radeon R9 290. Though the price tag is still nothing to be sniffed at (around £220), it compares favourably with Nvidia cards that are almost twice the price. All these highpowered parts are going to need plenty of air flow to keep them cool, so a nice big chassis with plenty of built-in fans will do the trick, and we suggest the Corsair Carbide 200R as it fits the bill nicely, for around £50.

We’ve once again gone for Intel processors for the gaming build. This isn’t due to any bias on our side (or money bags stashed under our desks) but because Intel processors have generally been ahead of AMD’s offerings, though AMD is gaining ground again.

Intel’s current crop, the fourth generation of Intel Core processors, boasts excellent speeds that benefit gamers. By the time you read this a brand new range of fourth generation processors

(codenamed Devil’s Canyon) should be available to buy, offering speed increases on the previous Haswell processors, for the same price. While the top of the range fourth gen processors have the i7 moniker, we’re recommending the i5 variant. This is because the main difference between the i7 and i5 processors is that i7s support Hyperthreading, and come with more threads in total (eight as opposed to six). This makes i7s great for intensive multitasking, such as video

encoding, but for gaming there is very little benefit – certainly not enough to justify the additional cost. It can be argued that the larger cache of an i7 processor (8MB compared to 6MB of an i5) is more important, but again with gaming you’re not going to see massive differences, which is why we recommend choosing an i5 processor and save your money – or even put it towards a better graphics card, which will definitely have more of an impact.

keep healthy. There are two main options here; air cooling and water cooling. Air cooling usually consists of big heatsinks and fans that sit over the processor. The pros of an air cooling system is that they are usually cheap and easy to install, with the cons being that they can be bulky and noisy.

Water cooling systems, on the other hand, use water to transfer the heat from the processor to a radiator situated elsewhere in the computer’s chassis. The benefits of water cooling is that they are more efficient and quieter than air coolers, and can also be less bulky and more flexible. The cons are that they can be more fiddly to install, and a bit more expensive. However, you can buy self-contained water cooler systems that come ready-prepared with coolant, so installation is pretty straightforward. While you might not be too keen on the idea of pumping liquid past your expensive electrical components, self-contained water coolers are perfectly safe and reliable. The choice of what to go for depends on how big your PC case is, how quiet you want your PC to be, how far you’re wanting to push your components and your budget. If you’re not going to be overclocking and you don’t mind a noisy PC, then air cooling will be a good choice, but if you want a quieter machine that’s better at keeping cool, then water cooling is the way to go.

You’re also going to want to get a dedicated graphics card

– and the one you go for depends on how well you want your gaming PC to run the latest and most graphically intense games. You can pay as little as £60 for a graphics card all the way to just shy of £1,000, so think carefully about what it is that you want from your machine.

Drivers and software

Historically, one of the biggest stumbling blocks for seeing significant growth in Linux gaming has been getting 3D graphics drivers to work. These drivers would at best be

proprietary, and at worst non-existent. Happily, there’s always been a dedicated community beavering away at open-source alternatives, which usually contain many of the same features as

the official drivers. Many distros also make it easy to choose between a proprietary and open source driver option, depending on your preference. In Ubuntu, for example, and its derivatives, you can find this by opening up System Settings, then clicking on Software & Updates. In the Ubuntu Software tab, click Proprietary Drivers for Devices to enable those drivers. Click the Additional Drivers tab to see what drivers are installed, and if any of them are proprietary.

If you’re using an Nvidia card, then the default drivers should be the open-source Nouveau drivers, which have been created by reverse engineering Nvidia’s proprietary graphics drivers for Linux. Though Nvidia has been far from a darling of the open source world, it has won plaudits by contributing to the open source driver recently. This should mean that there’s a better chance of feature parity between the open-source and proprietary drivers, which means there’s less cause to use the latter. You can find out more about Nouveau at http://nouveau.freedesktop.org. If you’re using an AMD graphics card, then the open source drivers should be installed by default as well. The proprietary drivers (known as Catalyst/fglrx) can be installed from the package manager. Note: make sure you uninstall and purge the old drivers first.

As far as the best distros go, although much has been made of Valve’s new game-centric distro SteamOS, it is still in its early days, so we’d hesitate to recommend it if you also want to use your PC for other day-to-day tasks. It’s worth keeping an eye on for the future, though. For the most compatible, and hassle free, experience, we’d recommend a Debian derivative, with Ubuntu or Mint being the best bet.

Proprietary drivers continue to plague GNU/Linux distros and will do for some time to come.

Shopping list

If you fancy building a PC that can sit unobtrusively in your living room and serve you all the media your eyes and ears can handle, then you’ll be pleased to know

that it’s extremely easy nowadays, and with a few choice distros you can create an excellent media machine that can be used comfortably with a TV.

While building a gaming PC is mainly about being big and brash, creating a decent media PC is a bit more nuanced affair. You don’t want powerful components – in fact in some cases you’ll want the opposite, as you’re going to be making a small machine that’s on for very long periods and that operates as quietly as possible, which means you don’t want to be generating much heat. Unless you don’t mind a big beige box sitting in the corner of your living room, then you’ll

Kodi (XBMC) is up to version 14, which is lucky for everyone.

want an attractive and compact case. Luckily, we’re spoilt for choice with small-form factor Micro-ATX chassis as they’ve become increasingly popular as integrated components have become more powerful and power efficient. We’ve gone for the Antec ISK310-150 Micro-ATX case as it’s compact and looks great.

Because of the format’s small size, it can be a bit fiddly, so if you want a bit more space and flexibility, we’d also recommend the Antec ISK 600. The Antec ISK310-150 MicroATX case comes with a built-in 150 watt power supply, which means that’s one less thing to worry about. The fan speed on the PSU can also be changed to make it as quiet as possible, though you’ll want to keep an eye on temperatures.

Perfectly formed parts

Because of the size of the chassis you’ll also need to choose an mini-ITX form factor motherboard. For this build we’d recommend the ASRock FM2A88X-ITX+, because not only does it have a compact design, but it also includes some pretty handy features for a media PC. It comes with not just a HDMI out port for connecting to a high definition TV, but also a HDMI in port for connecting other devices to it, particularly useful if your TV only has limited HDMI ports.

The motherboard also comes with built-in wireless 802.11n antennas, which gives you a bit more flexibility when placing the PC. This motherboard supports the FM2+ socket, as we recommend getting the AMD A8-7600 processor, thanks to its excellent onboard graphics, which keeps both the cost and the power consumption down. While a liquid cooler to keep the processor’s temperatures down is an ideal solution for a media PC, thanks to its relatively quiet performance, if you’re going for a small case then there probably won’t be enough room. If that’s the case, then the

organise and stream your media to other connected devices. Though originally a fork of XBMC, Plex now has taken on a life of its own and can be found on many Smart TVs and set top boxes, and uses a number of closed source and proprietary technologies. Though Plex Home Theater doesn’t have an official Linux version at the moment, there are builds available for certain distros, which you can find out more about at http://bit.ly/lxfplex.

An up and coming media centre distribution that we’re rather fond of at Linux Format is OpenELEC (which stands for Open Embedded Linux Entertainment Center). This is a lightweight Linux distribution that’s been built from scratch with media playing in mind. It’s also based on XBMC and is extremely easy to set up and can be installed on a whole host of hardware configurations, including, of course, the ridiculously popular Raspberry Pi.