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发信人: tian.bbs@bbs.tju.edu.cn.no.spam ( 专 ), 信区: Linux
标 题: [转载] Why is Linux Successful? - An Opinion.(转寄)
发信站: 天大求实BBS站 (Mon Jul 5 19:37:24 2004)
转信站: SZU!news.szu.edu.cn!news.xjtu.edu.cn!news.happynet.org!news2.happynet.o
【 以下文字转载自 tian 的信箱 】
【 原文由 tyxin@smth.edu.cn 所发表 】
发信人: pure (青衣～ Shadow in silence), 信区: FreeBSD
标 题: Why is Linux Successful? - An Opinion.
发信站: BBS 水木清华站 (Tue May 11 18:10:44 1999)
Why is Linux Successful? - An Opinion.
This article was first published for UniForum NZ 99 held at
Rotorua 13-17 April 1999. It is published with the permission
of the author who retains all rights.
Why is Linux Successful?
An Opinion.
Liam Greenwood
Wellington, New Zealand
20 March 1999
Is Linux successful?
Yes.
Why can I say that?
In 1999 Linux 'wins', all indicators go ballistic. Corel ports
WordPerfect to Linux. Informix and Oracle port their database
products to Linux. DB2 is shipped for Linux. IBM announces 7
x 24 support for Linux systems. Corel announces it will port all
its desktop applications to Linux. HP and SGI announce that
Linux is one of their 'core' operating systems. HP is porting
Linux to PA-Risc and announces that it will port Linux to
Merced. Datapro surveys have Linux on the top of the
reliability and functionality list in mid-range operating systems
comparison. Datapro also show Linux growth at 212%, the
only server OS other than NT to have positive growth
numbers. Gartner say Linux won't be a serious contender until
2000 and only if an industry heavyweight, such as IBM,
provides commercial support. Gartner has to reissue it's view
when IBM offers commercial support in March 1999. Also in
March, Dell state they will offer Linux as an operating system
option for workstations.
In the weekly IT press Linux column inches are up there with
the Microsoft column inches, only the Linux ones aren't about
being dragged through court. There are now a large number
of on-line linux news-papers, more than I can keep up with.
The Linux world has more happening in it than a single person
can keep up with. I try to keep up with
<http://www.slashdot.org>, <http://www.freshmeat.net>,
<http://www.linuxworld.com>, and <http://www.lwn.net>. The
events above are listed on those web pages. The really
amazing thing is that all four pages are updated daily, and
have probably no more than 25% overlap.
I can write a paper on Linux without an obligatory introduction
explaining what Linux is. All this on top of the fact that Linux
has been a reliable Unix work-alike for me since 1993. So,
yes, I can say that Linux is successful.
What is the 'competition'?
The Hurd
The HURD is the kernel for the GNU (Gnu Not Unix) operating
system. The HURD has had a version released in 1998, but
it's not yet of production quality. Richard Stallman has been
heard to say that they underestimated the amount of effort it
would take by about 10 years. However, in that time, of
course, the GNU project has built a substantial portion of an
operating system and Linux is a kernel that allows for the free
operating system to be shipped. The HURD has never really
been a competitor, as it wasn't available in the early 1990s
when Linux was coming to life.
386BSD/NetBSD/OpenBSD
386BSD is the first full OS made out of the BSD software
release that was called Net/2. NetBSD was created when the
386BSD initiator lost interest. OpenBSD is a recent version of
the NetBSD tree with a slightly different focus. 386BSD and
NetBSD were the two most likely to succeed when Linux was
starting.
FreeBSD
FreeBSD comes from the same lineage as the other *BSDs. It
differs in that it is a split motivated in part by the Linux
successes. It focused on be an excellent 386 based OS,
whereas the other BSDs all have multiple ports. It also made
ease of installation a focus. This was the most direct
competitor to Linux, up to Linux being ported to multiple
platforms.
Coherent/SCO/Solaris/BSDI/NT/HP-UX/AIX/IRIX
The commercial variants. Coherent has gone out of business,
possibly because the principals in the firm couldn't see the
importance of networking. No source, but the best Unix
manual ever written. Interestingly, of the other variants, SCO
and Solaris now provide free binary licenses for home and
educational use. Solaris started talking in March 1999 of
making the source code of Solaris available. When Linux was
being created the cost of a commercial Unix license was
prohibitively expensive for an individual.
Microsoft NT
.
They sell a lot.
Why?
I believe the primary reasons that Linux has gained a greater
mindshare than the other options boil down to:
support of cheap hardware
visibility on Usenet (marketing)
the USL lawsuit against BSD
There are a few other reasons which I go through below,
however I believe it is those three that have made the critical
difference at the right time. I'll now discuss those and some
other factors.
Time and place - 386 hardware hits affordable, Internet
hits available.
Timing is everything, and Linux has been the lucky one. Linux
had a university student with drive and programming talent at
the time when 80386 machines had become just affordable by
university students. Usenet was carried by non-USA
universities giving the developers a forum to discuss there
issues, and ftp gave Linus a distribution method. A year earlier
and 386s would have been out of reach for most university
students. A year earlier and access to the Internet may not
have hit the right critical mass.
Cheap hardware - MFM/IDE vs SCSI
Linux has always had a pragmatic view of hardware, whist the
BSDs carried a purist view. When I got my first 386 I had MFM
style disk drives. At that the BSDs only supported SCSI. Now
SCSI is undoubtedly the correct choice, however it did not
match the common hardware profile out in the market. Linux
had the advantage for the first three years that I ran it of
supporting a more diverse range of hardware than the BSDs.
The BSDs assumed you had purchased a machine to run a
Unix-style OS on, while Linux assumed you had a machine
and wanted to try Unix. Linux was much friendlier to someone
just wanting to dip their toes in the water. In this respect Linux
did something that the BSDs were unable to do to any great
degree - grow the Unix user base.
GNU/X Code leverage
Linux is just the kernel of an Operating System. Linus built a
kernel that made it easy to port existing POSIX/BSD/Unix code
to it. He also utilized the GNU compiler GCC on Minix to
bootstrap up his first kernels. From a start in December 1991
(when the first Linux code was released to the public) it took
less than two years to get to a usable system which was
entering a code-freeze at level 0.99 patch level 15 in
preparation for release 1.0 . It had editors, compilers, shells,
an X-base GUI, networking and even some games. It managed
to get that far that fast by leveraging off the work done by the
Free Software Foundation in its' GNU (GNU's Not Unix)
project. The GNU project provided the compilers, versions of
most of the standard Unix toolset such as gawk, grep etc,
BASH - the Bourne Again shell and emacs. If the GNU and X
projects had not existed it is unlikely that Linux would have
been a full featured functional operating system at that speed,
and the BSDs were waiting in the wings for Linux to falter.
Public development - Newsgroups vs Mailing lists
Remember that early 1990s was before the Web took off.
Usenet newsgroups and mailing lists were the pre-eminent
forms of many-to-many communication. In the BSD world all
communications took place on mailing lists. High
signal-to-noise ratio. The free BSDs didn't have their own
newsgroups, they shared with the commercial BSD. In terms
of volume that didn't matter as there was little activity there,
and all the developers were hidden away on mailing lists.
Linux on the other hand had a few very high volume
newsgroups. Surprisingly reasonable signal-to-noise ratio,
which improved a bit more when the newsgroup
re-organisation included an advocacy group for flamefests and
useless my-whatever-is-better-than-your arguments. It also
created an announce group and an answers group both
moderated, as well as the usual suite of other subgroups.
Rather than splitting the activity into multiple lower volume
groups what happened was that the volume in each
increased, so there were now many high volume groups.
Knowledgeable users and developers still frequented the
groups so the chances of getting your question answered or
your problem solved were still very good. For the experimenter
looking to try one of the free Unixs, it appeared that there was
nothing happening in the BSD camp, while the Linux joint was
jumpin'. The experimenter could find out about Linux, see what
was happening, ask questions and it supported his low-end
hardware. The FreeBSD team realised that being seen was
important and started frequenting the BSD newsgroups more,
however by then Linux had won the mindshare space in
Usenet. Again, this had the effect of growing the Unix user
population. For many high-school and university students over
the last 5 years Linux is not only the only Unix they have ever
been in
contact with - it's quite likely to be the only non-MS-Windows
operating system they have been exposed to.
Net/2 vs USL issue - *BSDs hit a snag, a new network
stack and a breathing space.
The AT&T spin-off responsible for the Unix product, Unix
Systems Labs (USL), claimed the Net/2 code base that
386BSD, NetBSD, FreeBSD plus the commercial startup BSDI
were based on included AT&T copyright code. It began legal
proceedings against both BSDI and the Regeants of the
University of California. At this time Berkeley was putting
together the final release of BSD Unix, BSD4.4, which was
held up by the litigation. In response to the proceedings
brought against them by USL the Regeants brought suit
against USL for use of Berkeley code without proper
attribution. The purchase of USL and the Unix trademark by
Novell saw the resolution of the problems with the agreement
to stop shipping Net/2 based systems, BSD released 4.4 and
the unencumbered code release called 4.4lite. As part of the
resolution the 4.4lite code base was given a clean bill of
health by Novell. Both NetBSD and FreeBSD moved to being
based entirely on the 4.4lite code base, NetBSD with version
1.0 and version 2.0 for FreeBSD (by then 386BSD was a dead
system, OpenBSD split well after this).
This litigation caused Linux to go its' own way with their
networking. At the time the networking was being developed
the USL/BSDI/UCB lawsuit unpleasantness was at full noise.
The networking developers didn't wish to be embroiled in all
the litigation so rather than leverage off the 'standard' and
robust BSD networking code they choose to roll their own.
A far more important effect insofar as this paper is concerned
is the uncertainty the lawsuit cast over the BSDs at a critical
time in the Linux development. The BSDs came from a rich
existing source code base. Particularly in the networking area
they were far more robust and mature than Linux. Users who
may have been attracted away from Linux were wary of
committing to one of the BSDs when it looked as though they
might lose the ability to develop free versions should the
lawsuit go USLs way. This gave Linux sufficient time to get up
to speed in respect of it's networking code and help halt
movement of people from Linux to *BSD.
Development model - Controlled Anarchy vs Core Team
The BSDs Development
The BSDs tend to have 'core' teams looking after the source
trees for the respective systems. Changes to the kernel which
a developer who is not on the core team wishes to have folded
into the base source tree are submitted to the team who will
vet the patches and merge it into the current source. The BSD
systems distribute a full system source tree, in that they
maintain a large proportion of a full system so when you do a
build you make a large proportion of your unix system.
This model seems do have directly arisen from Bill Jolitz, the
original 386BSD developer, losing interest. Patches to
386BSD were made available both to Bill Jolitz and to other
users of the system. Jolitz had declared his intention of a new
version of 386BSD however it didn't seem forthcoming, and
Bill became withdrawn from the 386BSD user community.
Given his apparent reluctance to work with others to improve
386BSD, a group of developers banded together to provide a
cohesive point of reference and co-ordination for the ongoing
development of the 386BSD system. This group itself soon
splintered into two groups, NetBSD and FreeBSD, and
subsequently also OpenBSD, due to personality clashes and
differing opinions on the direction of the development.
Benevolent Dictator - Linus for President
The Linux Development Model
The BSDs whole system model is in stark contrast to the linux
world. The kernel source tree and releases are managed by
Linus, developers submit code they wish to have folded into
the standard kernel source to Linus. Linus also decides when
to code-freeze the kernel prior to the release of a production
version.
Linux differs from the BSDs in that the person responsible for
the kernel takes no responsibility for the overall system. In this
respect there are various distributions based on the linux
kernel plus the rest of the programs needed for Unix style
system packaged up with the kernel. RedHat, Debian, S.U.S.e
and Caldera are examples of distributions.
This model allows Linux to maintain a facade of unity and
oneness while actually having far more diversity that in the
*BSD world. However when compared to the commercial Unix
world, Linux manages to be far less diverse in having a
common kernel, common libraries and much of the userworld
being common - mostly GNU. This seems to give Linux the
best of both worlds - a less fragmented market place for those
who wish to market things such as Oracle, or WordPerfect, yet
with a lot of flexibility for people to create their value-added
version of the system.
It has also given the illusion of a kernel and OS more open to
the individual developer. The BSD variants have all come
about from splits out of one or the other 'core' teams. Linus
take patch submissions from anyone - within his vision of
where the kernel should go. To date no-one has had sufficient
problem with this that they have started a kernel development
fork of their own. The kernel is only a part of the system, of
course, and the Linux model seems to encourage individuals
to develop new distributions. So what is seen as a negative in
the BSD world is seen as business as usual in the Linux
world. Overall Linux seems to have a more relaxed and
accepting development model for someone wanting to start
out.
Additionally having a figurehead makes it far easier for the
press to deal with the Linux phenomena, and probably helps
build that mindshare.
So in my opinion, the reasons that it's Linux making all the
waves rather than the BSDs or the commercial Unixs comes
down to low-cost of entry due to the pragmatically
promiscuous hardware support and high visibility from
conducting a large amount of business publicly in Usenet
newsgroups (and now on the web as well) and apparent easy
accessibility into the development.
--
看着她笑，他忽然觉得她好寂寞好寂寞。
她静静的看了他半天，才柔柔慢慢的:「 你好像已经找到了。」
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