There is no universal definition of the word "small" when it is used to define a Linux distribution. For some users, a small distribution is one that has a minimal footprint on a computer's resources. For others, a small distribution is the one that is distributed in a nifty little package and can be lugged around in a portable USB key. Both types of distributions have their uses. Small-footprint distros help save old and resource-strapped computers from ending up in a landfill, while USB-style distros give their users a safe, secure, and private environment on a public computer, like in a library or hotel lobby. The candidates we've selected in this article do a bit of both (see also the "Not Considered" box).

A lot of hardware is good enough to run the mainstream Linux distributions without any issues. However, the modern Linux desktop is a fairly resource hungry beast as well. Coupled with the fact that mainstream Linux distros are designed to appeal to a large number of users, they also have become too bloated. This has fueled the demand for lightweight options both for individual apps (see box titled "Lightweight Apps") and for complete distributions.

Just as it is difficult to define a distro as "small," defining hardware as "older" is also tricky. In addition to users who have hardware that's been outdated fairly recently, there's another kind who are holding on to their workhorses from the last decade. They usually just use their computer to browse the web, do some text editing, and watch some videos. It's a shame to force these users to dump their trusted machines and get the latest multicore computers loaded with several gigabytes of RAM or even a dedicated graphics card. However, chances are their workhorse isn't supported by the latest kernel, which keeps dropping support for older hardware that is no longer in vogue.

Carbon Dating Hardware

Forget about decades-old hardware; many popular distributions don't think it's viable to even support 32-bit architecture any more. Everything from new user projects such as Solus and elementary OS to the privacy-centric Tails Linux has dropped support for the 32-bit platform. Even mainstream projects like Arch and Ubuntu no longer offer installation ISOs for 32-bit machines. Despite the fact that 32-bit machines disappeared from the shelves quite a while back, they still adorn a lot of desks all over the world. Thankfully, you can still put these old machines to good use, and it really isn't a surprise that a large number of open source developers are working hard to make obsolete hardware usable again.

New software is always leveraging on the pace of hardware developments and rendering even relatively newer hardware obsolete. Examples of these relatively recent attic-ready hardware would be single-core or dual-core AMD Athlons and Intel Pentiums with about 2GB of RAM that they share with onboard graphics. A couple of years ago, mainstream distros would perform adequately on these machines, but not anymore. Then there are the hordes of netbooks that were pitched as light and portable replacements for laptops, but their under-powered hardware couldn't keep pace with the growing demands of the software. Using the distributions in this article, you'll be able to put your trusty old workhorse back into active service and even ensure you have a miniscule portable environment that you can safely use on a public computer. Whatever your needs, you'll be able to walk away with a distribution that meets your requirements.

Porteus

Porteus [1] is a portable distribution designed and optimized to run from removable media such as a USB flash drive, SD card, or even optical media like a CD. If the medium is writable, Porteus will save all changes inside a folder and load them on subsequent boots. The distribution is based on Slackware Linux using a modified version of the Linux Live scripts that help cut down bootup and shutdown times. The latest release supports newer UEFI machines and also includes the latest Intel firmware fix for the Spectre vulnerability.

Instead of a single ISO, Porteus is available as seven separate ISO images, each with a different desktop – from the heavyweight KDE and Cinnamon to the lightweight LXQt, LXDE, Openbox, and others. All seven flavors of Porteus support both 32- and 64-bit architectures, and the ISOs of most editions weigh in around 300MB each. This is because the distribution exists in a compressed state on the storage media, and the familiar Linux directory structure is created on-the-fly during boot.

Another unique aspect of Porteus is its use of modules, which are precompiled packages that you activate and deactivate as per your requirements. If you move these app modules to a designated directory inside the removable storage, the app is available in subsequent boots as well. The modules infrastructure works well in conjunction with the traditional binary packages. Porteus uses the Unified Slackware Package Manager (USM), which lets you fetch apps from across five different Slackware repositories. When you fetch packages via USM, you also get the option to convert them into modules (Figure 1). You can then activate the modules to use the app and make them survive reboots as well.

Figure 1: Depending on the desktop you choose, it can easily require up to 1GB of RAM to run Porteus.

Porteus has a unique mechanism for getting onto a writable medium. Instead of dd'ing its ISO file on to a USB stick, you need to loop mount it and copy its contents onto an ext4-formatted disk. Then run a script from inside the USB to make it bootable, and you're good to go. The process is explained in the official installation guide [2]. You can also install Porteus to an internal hard drive, though the developers don't recommend this option. Out of the box, Porteus doesn't ship with very many apps besides the ones that come with the desktop environment by default. But you can use USM and its repository to easily flesh out your environment and have them available on subsequent boots, which makes it very convenient (Figure 2).

Figure 2: Porteus v5.0, which is currently available as RC1, includes a browser installation script.

The Porteus boot menu offers some interesting options. For example, you can use the boot menu to copy the entire Live environment to RAM, which requires more than 768MB of system memory. You can also opt to boot Porteus in text mode, initialize a PXE server, or access the Plop boot manager. By default, the Live session is persistent, which automatically saves all changes made to the Live environment. However, you do get the option to start a fresh session from the boot menu.

Puppy Linux

One of my all-time favorites, Puppy Linux [3], was one of the first of the miniscule distributions. Puppy had its first release way back in 2003. The distribution is built from the ground up and has grown beyond its original mandate of resurrecting older hardware that had been rendered useless due to lack of support in the mainstream distributions.

The project currently has four official versions. Three are based on Ubuntu's Bionic, Xenial, and Tahr releases, and one is based on Slackware 14.1. Despite their different base and package repositories, all variants use JWM, which is one of the lightest window managers.

You can transfer Puppy Linux to a rewritable medium like a USB disk or anchor it to your hard disk. The distribution's custom installer will help you with both these installation targets. The distribution supports two installation mechanisms. The default frugal mechanism copies Puppy files inside a partition that holds another distribution, while the full option takes over the entire partition and is recommended only for older machines. Puppy's installation process is rather unconventional and might even intimidate first-time users, but every step is well documented and easy to follow.

Once you're done with the installation, you'll be amazed by the distribution's cache of apps. There's no beating Puppy for out-of-the-box functionality. You'll find an app for virtually every task that you can perform with a desktop computer. Puppy's menu includes popular lightweight options such as Claws Mail, the Pale Moon web browser, the AbiWord editor, the mpv multimedia player, and more (Figure 3). Interspersed with them are Puppy's own custom apps – primarily to ease administration tasks. For a miniscule distribution, Puppy has some apps that you wouldn't find even in full-fledged distributions, including apps to block online ads, a softphone for Internet telephony, a secure downloader, a DVD burning app, and lots more.

Figure 3: Not all Puppy variants ship with the same set of apps by default.

Puppy Linux packages are called pets and have a .pet extension. You can install packages using the distribution's custom Puppy Package Manager tool. By default, the package manager will fetch apps from the repositories of the Puppy variant you are using, but you can configure it to download packages from other Puppy repositories as well. You can also download SquashFS (SFS) files for some popular apps like Kodi, KdenLive, LibreOffice, WPS Office, and more (Figure 4). SFS files are compressed environments that package an app and all its dependencies. Think of them as modules in Porteus that can be activated and deactivated as well.

Figure 4: Some Puppy variants like Bionic Puppy include the custom Quickpet app to easily install popular applications.

When you shut down Puppy for the first time, the distribution offers to save all changes inside a file that can optionally be encrypted for added security. Speaking of security, it should be noted that the distribution runs everything as the root user. The Puppy developers consider this to be a safe option but also give you the option to run the distribution as a non-privileged user, although the non-privileged option is currently considered experimental. Interestingly, Puppy Linux can also save changes from a Live session onto rewritable optical media as well. Puppy also scores highly for its ample documentation. The distribution bundles help documentation on several topics, such as working with Microsoft Office files, how to add codecs, installing software, and more. Help pages contain links to the documentation pages for most applications.