Knoppix is one of the oldest Linux distributions still around, and it was one of the first Linux Live CD distributions.
If my memory is correct, the first generally available release of Knoppix (on a Live CD) was made sometime in late 2000. I don't think it is exaggerating to say that Knoppix set the standard for Live Linux distributions when it was released, or that the Linux world as a whole learned a lot about how Live distributions should be done, and how powerful, versatile and useful they could be.
Over the years, Knoppix has evolved and expanded. In about 2005 a Live DVD version was added, with loads of additional applications, utilities and packages included. Rather than drop the Live CD version, however, both formats have been maintained since then, with the CD version as a "small/fast/easy" alternative, and the DVD version as an "everything including the kitchen sink" alternative.
My first use of Knoppix came at SANS training classes, where they were using the Live CD version as a convenient way for course participants to gain access to Linux tools.
Those classes require attendees to bring their own laptops, and until a few years ago the majority of them would be running Windows. I have noticed in the last few years that more and more people are bringing dual-boot systems with both Windows and Linux, but that still doesn't eliminate the advantages of Live CD/DVD distributions of Knoppix (and Kali), because it is way more convenient to have a complete, bootable distribution with all the specific tools needed for the class ready to go, rather than to have to download and install them on whatever Linux system you brought along.
So, to get to the point rather than digressing about the history of it all: the latest release of Knoppix is 7.2.0, and it can be obtained from the Get Knoppix website.
It can be downloaded via BitTorrent or FTP/HTTP, or it can be ordered on CD, DVD or USB Flash Key. There is also one clear example of the "experience shows" that I mentioned above; for computers which cannot boot from USB drives (such as the Lifebook S2110 I am currently typing this on), there is also a "bootonly" CD version.
This is an extremely small download (about 12MB) which you can burn to a CD to be used together with the USB Flash drive version. When you boot the CD the first thing it does is switch over to the USB drive and continue running from there — how clever is that to get around old BIOS limitations?
I have downloaded both the CD and DVD images, so that I could compare them. I found the file list on the download site to be a bit confusing, so let me see if I can paraphrase it simply:
Whew. Hopefully one or two examples will make it all clear.
As far as I know these ISO images can only be burned to CD/DVD media, they are not the type of hybrid images which are becoming common, that can easily be converted to a bootable USB stick. I have tried with dd (no joy), but I haven't tried using unetbootin yet.
When you boot the Live image, the real fun starts. I have to admit that I just about jumped out of my chair when the woman's voice suddenly and completely unexpectedly announced "Initiating startup sequence"!
When it has finished booting, you get an LXDE desktop:
This release of Knoppix is running Linux kernel 3.9.6, with LXDE 5.x (I'm not experienced enough with LXDE to determine exactly what version, it seems like it's probably 5.4 or 5.5) and X.org X Server 1.12.4.
Oh, and it includes Compiz Fusion, with lots of desktop effects enabled! I found this to be a particularly amusing experience, using what is generally thought of as a "lightweight desktop", but with wobbly windows, animations when windows open or close, a desktop selection cube and heaven knows what else.
This system was installed from the DVD distribution, and as I said above, that is really the "all in" version. It is absolutely chock full of applications, utilities, packages and even alternative desktops. I will only give a few examples from each menu:
Honestly, I just picked those at random. If you download and boot the DVD, and then just look at the LXDE menus, I promise you it will amaze you.
If you boot from the CD version, rather than the DVD, what you get is still a nicely configured LXDE system, but without the massive amount of additional software.
Just glancing at the above list, the CD version has "only" Iceweasel, GIMP and Image Magick, LibreOffice, MPlayer, Install to Flash/HD, Midnight Commander and Leafpad. Besides not having the KDE and Gnome desktops and their associated programs and utilities, it does not have the Programming menu at all, and it does not have WINE.
When running either the Live CD or DVD version, you can choose 'Install to HD' from the Knoppix menu to make a permanent hard drive installation. There are a few useful things to know about this.
First, the Knoppix installer (called 0wn, for Zero Work Needed), is not at all like any other installer you might have used for another Linux distribution. 0wn does the minimum work necessary to copy the Live image to a hard drive partition and make it bootable.
It doesn't worry about niceties such as setting up timezones, keyboard maps and user accounts, and it doesn't have any flexibility at all when it comes to disk partitions and filesystems. It will install to an empty 'reiserfs' partion, and nothing else — no ext2/3/4/btrfs or whatever need apply.
If you already have the necessary partition, 0wn will find it and offer to use it for the installation. If you don't have a suitable partition 0wn will let you run gparted so that you can create one, or it will offer to automatically partition the disk for you - it would take a brave person, or a totally empty hard drive, to accept that last offer, in my opinion.
Once it has copied the Live image to the hard drive, it will offer to set up GRUB for you. It only knows how to set up grub-pc (Legacy GRUB), not even grub2, much less UEFI boot. If you already have some kind of MBR bootloader installed, you can tell it not to install GRUB.
In this case it still has the GRUB package installed, and the necessary config files are complete (such as /boot/grub/menu.lst), it just doesn't try to set the MBR to point to the Knoppix partition.
The Live CD image is a 700MB ISO, but it expands to 2GB when unpacked to the hard drive. The DVD image is a 3.8GB ISO which expands to 10GB when installed to the hard drive. Keep these sizes in mind when you are setting up the partitions for Knoppix.
In the DVD version, on the Knoppix menu there is an item called 'Choose/Restart KNOPPIX Desktop'.
It is exactly what the name implies, it puts up the window shown here, listing the available desktops, you can select the one you want and then OK, and it will configure that and then restart the X server, all without rebooting or even logging out. You need to be a bit careful about this, because restarting the X server will terminate all running programs which have graphical output. Keep that in mind, or you will get a rather unpleasant surprise when you try it.
If you select the KDE desktop and then click OK, after the X server restarts you will get this:
That is a very typical looking KDE desktop. As you might guess from what is shown in this screen shot, the KDE menus have the same structure and content as the LXDE menus had.
If you select the Gnome Desktop, you will get this:
Again, that is a pretty typical Gnome 3 desktop, with the application menus structure and content the same as for the LXDE and KDE desktops seen above.
So, in summary: Knoppix is a well-established, well-known and very stable Linux distribution.
It is best known as a Live CD/DVD version, which many experienced Linux users keep handy for system recovery, hardware compatibility testing, and ad-hoc Linux shows (oh, and for students at SANS security classes).
Knoppix is not only interesting as a Live distribution, though: it can be installed to hard disk quite easily, and makes a very nice Linux system.
The Knoppix installer (0wn) is a bit, uh, different. Many people consider the Fedora installer 'anaconda' to be the height of complexity; I don't necessarily agree with that, but if I were to look at it that way I would consider the Knoppix installer to be the opposite extreme, the height of minimalism.
The Knoppix CD distribution is a good, well-equipped LXDE desktop, but if you want more than that the DVD distribution has LXDE, KDE and Gnome and an easy utility to select and switch between them.
If you are seriously interested in Linux, and you have never tried Knoppix, you owe it to yourself to download one of the Live images and at least give that a try.