Linus Torvalds rarely makes appearances at conferences, and it's even
less common for him to get up in front of the crowd and speak. He made an
exception for LinuxCon Brazil, though, where he and Andrew Morton appeared
in a question and answer session led by Linux Foundation director Jim
Zemlin. The resulting conversation covered many aspects of kernel
development, its processes, and its history.
Jim started things off by asking: did either Linus or Andrew ever expect
Linux to get so big? Linus did not; he originally wrote the kernel as a
stopgap project which he expected to throw away when something better came
along. Between the GNU Project and various efforts in the BSD camp, he
thought that somebody would surely make a more capable and professional
kernel. Meanwhile, Linux was a small thing for his own use. But, in the
end, nothing better ever did come along.
Andrew added that, as a kernel newbie (he has "only" been hacking on it for
ten years), he has less of a long-term perspective on things. But, to him,
the growth of Linux has truly been surprising.
How, Jim asked, do they handle the growth of the kernel? Andrew responded
that, as the kernel has grown, the number of developers has expanded as
well. Responsibility has been distributed over time, so that he and Linus
are handling a smaller proportion of the total work. Distributors have
helped a lot with the quality assurance side of things. At this point,
Andrew says, responsibilities have shifted to where the kernel community
provides the technology, but others take it from there and turn it into an
Linus noted that he has often been surprised at how others have used Linux
for things which do not interest him personally at all. For example, he
always found the server market to be a boring place, but others went for it
and made Linux successful in that area. That, he says, is one of the key
strengths of Linux: no one company is interested in all of the possible
uses of the system. That means that nobody bears the sole responsibility
of maintaining the kernel for all uses. And Linus, in particular, really
only needs to concern himself with making sure that all of the pieces come
together well. The application of a single kernel to a wide range of use
cases is something which has never worked well in more controlled
From there, Jim asked about the threat of fragmentation and whether it
continues to make sense to have a single kernel which is applicable to such
a wide range of tasks. Might there come a point where different versions
of the kernel need to go their separate ways?
According to Linus, we are doing very well with a single kernel; he would
hate to see it fragment. There are just too many problems which are
applicable in all domains. So, for example, people putting Linux into
phones care a lot about power management, but it turns out that server
users care a lot too. In general, people in different areas of use tend to
care about the same things, they just don't always care at the same time.
Symmetric multiprocessing was once only of interest to high-end server
applications; now it is difficult to buy a desktop which does not need SMP
support, and multicore processors are moving into phones as well. Therein
lies the beauty of the single kernel approach: when phone users need SMP
support, Linux is there waiting for them.
Andrew claimed that its wide range of use is the most extraordinary technical
attribute of the kernel. And it has been really easy to make it all work. It is
true, though, that this process has been helped by the way that "small"
devices have gotten bigger over time. Unfortunately, people who care about
small systems are still not well represented in the kernel community. But
the community as a whole cares about such systems, so we have managed to
serve the embedded community well anyway.
Next question: where do kernel developers come from, and how can Brazilian
developers in particular get more involved? Linus responded that it's
still true that most kernel developers come from North America, Europe, and
Australia. Cultural and language issues have a lot to do with that
imbalance. When you run a global project, you need to settle on a common
language, and, much to Linus's chagrin, that language wasn't Finnish. It
can be hard to find people in many parts of the world who are
simultaneously good developers and comfortable interacting in English.
What often works is to set up local communities with a small number of
people who are willing to act as gateways between the group and the wider
Andrew pointed out that participation from Japan has grown significantly in
recent years; he credited the work done by the Linux Foundation with
helping to make that happen. He also noted that working via email can be
helpful for non-native speakers; they can take as much time as needed at
each step in a conversation. As for where to start, his advice was to Just
Start: pick an interesting challenge and work on it.
Open source software, Linus said, is a great way to learn real-world
programming. Unlike classroom projects, working with an active project
with people and addressing big problems. Companies frequently look at who
is active in open source projects when they want to find good technical
people, so working on such projects is a great way to get introduced to the
world. In the end, good programmers are hard to find; they will get paid
well, often for working on open source software. Andrew agreed that having
committed changes makes a developer widely visible. At Google, he is often
passed resumes by internal recruiters; his first action is always to run
git log to see what the person has done.
Linus advised that the kernel might not be the best place for an aspiring
developer to start, though. The kernel has lots of developers, and it can
be kind of scary to approach sometimes. Smaller projects, instead, tend to
be desperate for new developers and may well be a more welcoming
environment for people who are just getting started.
At this point, a member of the audience asked about microkernel
architectures. Linus responded that this question has long since been
answered by reality: microkernels don't work. That architecture was seen
as an easy way to compartmentalize problems; Linus, too, originally thought
that it was a better way to go. But a monolithic kernel was easier to
implement back at the beginning, so that's what he did. Since then, the
flaw in microkernel architectures has become clear: the various pieces have
to communicate, and getting the communication right is a very hard
problem. A better way, he says, is to put everything you really need into
a single kernel, but to push everything possible into user space.
What about tivoization - the process of locking down Linux-based systems so
that the owner cannot run custom kernels? Linus admitted to having strong
opinions on this subject. He likes the fundamental bargain behind
version 2 of the GPL, which he characterizes as requiring an exchange
of source code but otherwise allowing people to do whatever they want with
the software. He does not like locked-down hardware at all, but, he says,
it's not his hardware. He did not develop it, and, he says, he does not
feel that he has any moral right to require that it be able to run any
kernel. The GPLv2 model, he feels, is the right one - at least, for him.
Licensing is a personal decision, and he has no problem with other projects
making different choices.
Another member of the audience questioned the single-kernel idea, noting
that Android systems are shipping kernels which differ significantly from
the mainline. Jim responded that people who created forked versions of the
kernel always come back - it's just too expensive to maintain a separate
kernel. Andrew said that the Android developers are "motivated and
anxious" to get their work upstream, both because it's the right thing to
do and because the kernel changes too quickly. Nobody, he says, has the
resources to maintain a fork indefinitely.
Linus cautioned that, while forks are generally seen as a bad thing, the
ability to fork is one of the most important parts of the open source
development model. They can be a way to demonstrate the validity of an
idea when the mainline project is not ready to try it out. At times, forks
have demonstrated that an approach is right, to the point that the kernel
developers have put in significant work to merge the forked code back into
the mainline. In the end, he says, the best code wins, and a fork can be a
good way to show that specific code is the best. Rather than being scary,
forks are a good way to let time show who is right.
Another audience member asked Linus if he would continue to
work on the kernel forever. Are there any other projects calling to him?
Linus said that "forever is a long time." That said, he'd originally
thought that the kernel was a two-month project; he is still doing it
because it stays interesting. There are always new problems to solve and new
hardware to support; it has been an exciting project for 19 years and he is
planning to continue doing it for a long time. He may have an occasional
dalliance elsewhere, like he did when writing Git, but he always comes back
to the kernel because that's where the interesting problems are.
Jim described Linus and Andrew as a couple of the most influential people
in technology. They are, he said, at the same level as people like Bill
Gates, Steve Jobs, and Larry Ellison. Those people are some of the richest
in the world. His questions to Linus and Andrew were: "are you crazy?" and
"what motivates you?"
Andrew replied that his work is helping people getting what they want
done. It is cool that this work affects millions of people; that is enough
In typical fashion, Linus answered that he is just the opposite: "I don't
care about all you people." He is, he says, in this for selfish reasons.
He was worried about finding a way to have fun in front of a computer; the
choice of the GPL for Linux made life more fun by getting people involved.
He has been gratified that people appreciate the result - that, he says, gives
meaning to life in a way that money does not. It is, he says, "taking by
The session ended with a short speech from Jim on the good things that
Linus and Andrew have done, followed by a standing ovation from the
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