Linux is not only about the
kernel, code, optimization, performance,Open Source, Copyleft, and the like.
There’s more–we’re actually beginning to see a culture emerging. I
said "Linux Culture"–what gets talked around when a bunch
of Linux users or programmers or both get together. As a Linux newbie, you
have to survive all this and much more. And as a newbie, you must remember
that you’re always playing catching up, given the current Linux arena. To
help a newbie get a perspective of what the world out there is, here’s a
set of answers to specific FAQs.
This FAQ is devoted to
ensuring that you can survive hanging out in the company of cool Linux
geeks. In addition, it’ll teach you all the terminology and buzzwords,
that if used well, will safely take you from plain old window washing to
sitting in that plush office, watching others wash windows.
This FAQ is structured for maximum user
comfort and has two levels–beginner and advanced. If you’re smart,
aware, and put-your-neck-on-the-line types, choose the intelligent answers
when asked such questions. If you just want to play safe and live, choose
the safe answers. If you ever thought that the Linux world was one safe,
happy, and peaceful place, here’s your guide to the most tricky holes that
can be encountered.
What’s this Linux?
Intelligent
Answer: Did I hear that right?
Safe Answer:
An operating system, whose heart is copyright…err…copyleft, as well as
Linus Torvalds.
The official definition off
the FAQs goes something like this.
Linux is the kernel of
operating systems that looks like and performs as well or better than the
famous operating system from AT&T Bell Labs.
Linus Torvalds and a loosely
knit team of volunteer hackers from across the Internet wrote (and are still
writing) Linux from scratch. It has all the features of a modern,
full-fledged operating system–true multitasking, virtual memory,
libraries, demand loading, shared, copy-on-write executables, proper memory
management, and TCP/IP networking.
Unless you know all those
terms like the back of your hand and have a CS degree or two, it may not be
wise to use that definition. The heart of Linux–the kernel–is all that
was (not so much anymore) the work of Linus Torvalds. Most of the remaining
parts have been put together mostly from work of the GNU Foundation (below).
Linus is no longer a poor old student who couldn’t access Unix, but a rich
researcher working in a hush-hush company called Transmeta. He still,
however, retains his refreshing sense of humor.
Why the penguin?
Intelligent
Answer: Never bird watched, you
monster?
Safe Answer: Linus.
Tux is the name of the
official penguin, mascot of Linux. He is quite happy, contented, and chubby.
Just like what you and me should be. The only difference is that he gets to
be, while you and me want to be. The original drawing by Larry Ewing has now
seen countless versions with Tux holding this, that and the other.
While the legend goes that a
penguin assaulted Linus in Antarctica, the actual happy accident took place
in Australia.The famous quote from Linus that details the choice is, "If
you think penguins are fat and waddle, you have never been attacked by one
running at you in excess of 100 MPH." To this day, the wisdom of
Linus is still evident. Pretty adolescent girls, young children, and very
interesting women swoon at the sight of the oh-so-cute penguin. No harm done
for the OS if the mascot is as adorable as hell–"sitting there with a
beatific smile" and planning world domination on the side.
You might ask
yourself why adding Win NT or 2000 machines should be any different from
adding Win 9x machines. However, there are significant differences in the
SMB implementations between versions of Microsoft’s own operating systems.
Even the password algorithms used by the two operating systems are
different. Win 9x machines don’t actually participate in a Win NT domain
the way NT does. The domain controller in this case is used purely for
authentication.
If you want to use Win 2000
machines in a Samba domain, you’ll need to upgrade to Samba 2.0.7 (Zoot
ships with 2.0.6, so you’ll have to download the updated RPMs). There are
a few subtle changes in 2000, most of which have been addressed in this
release. There are a few outstanding bugs though, but no show-stoppers. Note
that Win 2000 is currently only supported in the backwards compatibility
(with NT PDC) mode, and not in its native domain controller mode.
Adding a Samba server to a
Win NT domain
To get a
Samba server to join a Win NT domain, you must first create a machine
account for the server in the PDC’s SAM (Security Accounting Manager)
database. You can do this using the "Server Manager for Domains"
utility on the PDC. The machine account is created using the netbios name of
the Samba server, which is usually, but not necessarily, its host name.
Once you’ve created the
machine account, you need to configure the smb.conf file. Apart from the
standard configuration, you need to make the following changes:
workgroup = NTDOM (Assume
that the domain name is NTDOM)
security = domain
password server = NTDOMPDC
NTDOMBDC1 NTDOMBDC2
where NTDOMPDC is the name of
the domain controller, NTDOMBDC<1,2> are the names of the backup domain
controllers, and SAMBA is the netbios name of the samba server.
Now, before restarting the
smbd daemons, give the command
# smbpasswd -j NTDOM -r
NTDOMPDC
This command will create a
file called SAMBA.NTDOM.mac in your /etc/ directory, containing the machine
account password for the Samba server.
Assuming all goes well, you
should get a message saying
smbpasswd :
Joined domain NTDOM
To add
a Win NT machine to a Samba domain, you need to create a user entry
for it in the password file. This is the Samba equivalent of creating a
machine account in the SAM database. The username should be the name of the
machine, appended with a "$". Set no password, and set the home
directory to /dev/null, and shell to /bin/false. (You might have to escape
the "$" on the command line with a "\", if required)
# useradd ntserver$ -s /bin/false -d /dev/null
The next step
is to go to the NT machine, and set the domain name to SAMBADOM (where
SAMBADOM is the domain name). Take care not to check the "create a
machine account" check box. This feature is not yet supported. You
should get a message saying "Welcome
to the SAMBADOM domain".
Understanding server
configuration options
If you look
at the man page for the smb.conf file (man 5 smb.conf), you’ll find a
number of configuration options that you can use to tweak the performance
and customize your Samba configuration further. Due to the lack of space
here, I’ll take a look at only a few configuration options.
One of the more misunderstood
configuration parameters is the "security=" option. We’ll take a
brief look at what the various options mean.
security=share
This is the conventional, and
most brain-dead option available. Shares exported will be available to any
machine in the workgroup without further authentication. This is commonly
used for machines sharing public shares, CD-ROMs, etc. Use this only when
you have no security concerns whatsoever.
security=server
Server level security is used
when you want the Samba server to authenticate users against another Samba
or Windows NT machine acting as a domain controller. This is a good idea
when you have a number of machines on your network, with users needing to
logon to the domain to be able to access the shares. In this case, you’ll
have to configure the "password server" parameter to specify the
names of the authentication servers (normally the PDC and BDC).
security=user
In this scheme, the Samba
server actually acts as a workgroup controller, authenticating Windows NT
and Win 9x clients. A separate user list has to be maintained, and users are
added using the "smbpasswd" command. In this case, the Samba
server maintains its equivalent of an NT SAM database.
security=domain
Domain level security is used
in the case described above, when adding a Samba server to a Win NT domain.
Here too, you’ll need to specify the "password server"
parameter. So how’s this different to the "security=server"
configuration? For one, when using server level security, the Samba server
will open and maintain a network connection to the domain controller during
the entire session. This can be a significant drain on network resources. In
domain level security, a connection is established for exchanging
authentication information only.
There are some new parameters
in Samba 2.0.7 as well. Most of these deal with the new utmp and wtmp
support (experimental, I might add) included in this version. This will
enable users logged in via Samba to be seen using the "who"
command, and all login information to be recorded in the system logs, not
just the samba logs. You’ll need to specifically compile support for this
using the
"–with-utmp" flag to "configure".
Samba
development is progressing at an extremely hectic pace. There are currently
four trees under active development (For those new to the open source style
of development, a "tree" consists of all the latest source code of
the software, to which developers have access. Developers "check
in" portions of code they are working on, and then "check
out" the new code for others to test and debug when they have
finished).
There is the SAMBA_STABLE
branch, which has the regularly released "stable code", for you
and me to use. New features are not introduced into this tree until they’ve
been thoroughly tested in unstable versions. The stable Samba tree at this
time doesn’t have the ability to be a domain controller for Win NT
machines.
The second branch is the
SAMBA_TNG branch, which is where the main thrust of development is going on
at the moment. TNG stands for "The Next Generation", and includes
all the "cool code", such as domain controller for NT and Win 2000
machines, support for NT- specific administrative tools such as "User
Manager for Domains", and trust relationships, etc.
The Third branch is the
SAMBA_HEAD branch, which is the successor to the current 2.0.x series. It
contains improved file and print sharing services and NT file permissions
support. However, it contains no NT PDC support.
The last and final branch is
the HEAD_WITH_TNG branch, which is exactly what you might imagine from its
name.
The most interesting of these
branches is the SAMBA_TNG branch, which focuses on Win NT PDC controller
code. It currently suffers from poor file serving ability, but code mergers
with the SAMBA_HEAD branch will take care of this problem in the near
future.
So if you’re a hacker, or
kid with a network and time to spare, download the TNG or HEAD branch and
play with the code. Finding bugs or contributing documentation is the
easiest way to help the development effort, if you’re not a developer
yourself.
Babu Kalakrishnan, a Director at Sankya System & Objects, Bangalore www://www.sankya.com