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Linux Speak: FAQ 

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PCQ Bureau
New Update

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.

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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?

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Intelligent

Answer: Did I hear that right?

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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.

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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?

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Intelligent

Answer: Never bird watched, you

monster?

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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.

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Interacting with NT

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

Adding an NT server to a

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

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

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