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More consolidation, hence the removal of several files. 

Binh.
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LDP/guide/docbook/Linux-Networking/DHCP.xml
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<sect1 id="DHCP">
<title>DHCP</title>
<para>
Endeavouring to maintain static IP addressing to maintain static IP addressing
information, such as IP addresses, subnet masks, DNS names and other
information on client machines can be difficult. Documentation becomes lost or
out-of-date, and network reconfigurations require details to be modified
manually on every machine.
</para>
<para>
DHCP (Dynamic Host Configuration Protocol) solves this problem by providing
arbitrary information (including IP addressing) to clients upon request.
Almost all client OSes support it and it is standard in most large networks.
</para>
<para>
The impact that it has is most prevalent it eases network administration,
especially in large networks or networks which have lots of mobile users.
</para>
2. DHCP protocol
DHCP (Dynamic Host Configuration Protocol), is used to control
vital networking parameters of hosts (running clients) with the help
of a server. DHCP is backward compatible with BOOTP. For more
information see RFC 2131 (old RFC 1541) and other. (See Internet
Resources section at the end of the document). You can also read
[32]http://web.syr.edu/~jmwobus/comfaqs/dhcp.faq.html.
4.5. Other interesting documents
Linux Magazine has a pretty good article in their April issue called
[62]Network Nirvana: How to make Network Configuration as easy as DHCP
that discusses the set up for DHCP.
References
1. DHCP.html#AEN17
2. DHCP.html#AEN19
3. DHCP.html#AEN24
4. DHCP.html#AEN41
5. DHCP.html#AEN45
6. DHCP.html#AEN64
7. DHCP.html#AEN69
8. DHCP.html#AEN74
9. DHCP.html#AEN77
10. DHCP.html#SLACKWARE
11. DHCP.html#REDHAT6
12. DHCP.html#AEN166
13. DHCP.html#AEN183
14. DHCP.html#DEBIAN
15. DHCP.html#AEN230
16. DHCP.html#NAMESERVER
17. DHCP.html#AEN293
18. DHCP.html#TROUBLESHOOTING
19. DHCP.html#AEN355
20. DHCP.html#AEN369
21. DHCP.html#DHCPSERVER
22. DHCP.html#AEN382
23. DHCP.html#AEN403
24. DHCP.html#AEN422
25. DHCP.html#AEN440
26. http://www.oswg.org/oswg-nightly/DHCP.html
27. http://www.linux.org.tw/CLDP/mini/DHCP.html
28. http://www.linux.or.jp/JF/JFdocs/DHCP.html
29. ftp://cuates.pue.upaep.mx/pub/linux/LuCAS/DHCP-mini-Como/
30. mailto:vuksan-feedback@veus.hr
31. http://www.opencontent.org/opl.shtml
32. http://web.syr.edu/~jmwobus/comfaqs/dhcp.faq.html
33. mailto:sergei@phystech.com
34. ftp://ftp.phystech.com/pub/
35. http://www.cps.msu.edu/~dunham/out/
36. ftp://metalab.unc.edu/pub/Linux/system/network/daemons
37. ftp://ftp.phystech.com/pub/
38. DHCP.html#NAMESERVER
39. DHCP.html#LINUXPPC-RH6
40. mailto:alexander.stevenson@home.com
41. DHCP.html#NAMESERVER
42. ftp://ftp.redhat.com/pub/redhat/redhat-4.2/i386/RedHat/RPMS/dhcpcd-0.6-2.i386.rpm
43. DHCP.html#SLACKWARE
44. mailto:nothing@cc.gatech.edu
45. DHCP.html#NAMESERVER
46. http://ftp.debian.org/debian/dists/slink/main/binary-i386/net/
47. DHCP.html#SLACKWARE
48. mailto:heiko@os.inf.tu-dresden.de
49. DHCP.html#NAMESERVER
50. DHCP.html#REDHAT6
51. ftp://ftp.linuxppc.org/
52. ftp://ftp.phystech.com/pub/dhcpcd-1.3.17-pl9.tar.gz
53. DHCP.html#TROUBLESHOOTING
54. mailto:nothing@cc.gatech.edu
55. DHCP.html#ERROR3
56. ftp://vanbuer.ddns.org/pub/
57. DHCP.html#DHCPSERVER
58. mailto:mellon@isc.org
59. ftp://ftp.isc.org/isc/dhcp/
60. http://www.kde.org/
61. ftp://ftp.us.kde.org/pub/kde/unstable/apps/network/
62. http://www.linux-mag.com/2000-04/networknirvana_01.html
</sect1>

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<sect1 id="Database">
<title>Database</title>
<para>
Most databases are supported under Linux, including Oracle, DB2, Sybase, Informix, MySQL, PostgreSQL,
InterBase and Paradox. Databases, and the Structures Query Language they work with, are complex, and this
chapter has neither the space or depth to deal with them. Read the next section on PHP to learn how to set
a dynamically generated Web portal in about five minutes.
We'll be using MySQL because it's extremely fast, capable of handling large databases (200G databases aren't
unheard of), and has recently been made open source. It also works well with PHP. While currently
lacking transaction support (due to speed concerns), a future version of MySQL will have this opt
</para>
* Connecting to MS SQL 6.x+ via Openlink/PHP/ODBC mini-HOWTO
* Sybase Adaptive Server Anywhere for Linux HOWTO
</sect1>

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<sect1 id="Email">
<title>Email</title>
<para>
Alongside the Web, mail is the top reason for the popularity of the Internet. Email is an inexpensive and fast method of time-shifted messaging which, much like the Web, is actually based around sending and receiving plain text files. The protocol used is called the Simple Mail Transfer Protocol (SMTP). The server programs that implement SMTP to move mail from one server to another are called Mail Transfer Agents (MTAs).
</para>
<para>
In times gone by, users would Telnet into the SMTP server itself and use a command line program like elm or pine to check ther mail. These days, users run email clients like Netscape, Evolution, Kmail or Outlook on their desktop to check their email off a local SMTP server. Additional protocols like POP3 and IMAP4 are used between the SMTP server and desktop mail client to allow clients to manipulate files on, and download from, their local mail server. The programs that implement POP3 and IMAP4 are called Mail Delivery Agents (MDAs). They are generally separate from MTAs.
</para>
* Linux Mail-Queue mini-HOWTO
* The Linux Mail User HOWTO
</sect1>

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<sect1 id="FTP">
<title>FTP</title>
<para>
File Transport Protocol (FTP) is an efficient way to transfer files between
machines across networks and clients and servers exist for almost all platforms
making FTP the most convenient (and therefore popular) method of transferring
files. FTP was first developed by the University of California, Berkeley for
inclusion in 4.2BSD (Berkeley Unix). The RFC (Request for Comments)
documents for the protocol is now known as RFC 959 and is available at
ftp://nic.merit.edu/documents/rfc/rfc0959.txt.
</para>
<para>
There are two typical modes of running an FTP server - either anonymously or
account-based. Anonymous FTP servers are by far the most popular; they allow
any machine to access the FTP server and the files stored on it with the same
permissions. No usernames or passwords are transmitted down the wire.
Account-based FTP allows users to login with real usernames and passwords.
While it provides greater access control than anonymous FTP, transmitting real
usernames and password unencrypted over the Internet is generally avoided for
security reasons.
</para>
<para>
An FTP client is the userland application that provides access to FTP
servers. There are many FTP clients available. Some are graphical, and
some are text-based.
</para>
* FTP HOWTO
</sect1>

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<sect1 id="NTP">
<title>NTP</title>
<para>
Time synchorinisation is generally considered important in the computing
environment. There are a number of reasons why this is important: it makes
sure your scheduled cron tasks on your various servers run well together,
it allows better use of log files between various machines to help
troubleshoot problems, and synchronised, correct logs are also useful if
your servers are ever attacked by crackers (either to report the attempt
to organisations such as AusCERT or in court to use against the bad guys).
Users who have overclocked their machine might also use time synchronisation
techniques to bring the time on their machines back to an accurate figure
at regular intervals, say every 20 minutes of so. This section contains an
overview of time keeping under Linux and some information about NTP, a
protocol which can be used to accurately reset the time across a computer
network.
</para>
2. How Linux Keeps Track of Time
2.1. Basic Strategies
<para>
A Linux system actually has two clocks: One is the battery powered
"Real Time Clock" (also known as the "RTC", "CMOS clock", or "Hardware
clock") which keeps track of time when the system is turned off but is
not used when the system is running. The other is the "system clock"
(sometimes called the "kernel clock" or "software clock") which is a
software counter based on the timer interrupt. It does not exist when
the system is not running, so it has to be initialized from the RTC
(or some other time source) at boot time. References to "the clock" in
the ntpd documentation refer to the system clock, not the RTC.
</para>
<para>
The two clocks will drift at different rates, so they will gradually
drift apart from each other, and also away from the "real" time. The
simplest way to keep them on time is to measure their drift rates and
apply correction factors in software. Since the RTC is only used when
the system is not running, the correction factor is applied when the
clock is read at boot time, using clock(8) or hwclock(8). The system
clock is corrected by adjusting the rate at which the system time is
advanced with each timer interrupt, using adjtimex(8).
</para>
<para>
A crude alternative to adjtimex(8) is to have chron run clock(8) or
hwclock(8) periodically to sync the system time to the (corrected)
RTC. This was recommended in the clock(8) man page, and it works if
you do it often enough that you don't cause large "jumps" in the
system time, but adjtimex(8) is a more elegant solution. Some
applications may complain if the time jumps backwards.
</para>
<para>
The next step up in accuracy is to use a program like ntpd to read the
time periodically from a network time server or radio clock, and
continuously adjust the rate of the system clock so that the times
always match, without causing sudden "jumps" in the system time. If
you always have a network connection at boot time, you can ignore the
RTC completely and use ntpdate (which comes with the ntpd package) to
initialize the system clock from a time server-- either a local server
on a LAN, or a remote server on the internet. But if you sometimes
don't have a network connection, or if you need the time to be
accurate during the boot sequence before the network is active, then
you need to maintain the time in the RTC as well.
</para>
2.2. Potential Conflicts
<para>
It might seem obvious that if you're using a program like ntpd, you
would want to sync the RTC to the (corrected) system clock. But this
turns out to be a bad idea if the system is going to stay shut down
longer than a few minutes, because it interferes with the programs
that apply the correction factor to the RTC at boot time.
</para>
<para>
If the system runs 24/7 and is always rebooted immediately whenever
it's shut down, then you can just set the RTC from the system clock
right before you reboot. The RTC won't drift enough to make a
difference in the time it takes to reboot, so you don't need to know
its drift rate.
</para>
<para>
Of course the system may go down unexpectedly, so some versions of the
kernel sync the RTC to the system clock every 11 minutes if the system
clock has been adjusted by another program. The RTC won't drift enough
in 11 minutes to make any difference, but if the system is down long
enough for the RTC to drift significantly, then you have a problem:
the programs that apply the drift correction to the RTC need to know
*exactly* when it was last reset, and the kernel doesn't record that
information anywhere.
</para>
<para>
Some unix "traditionalists" might wonder why anyone would run a linux
system less than 24/7, but some of us run dual-boot systems with
another OS running some of the time, or run Linux on laptops that have
to be shut down to conserve battery power when they're not being used.
Other people just don't like to leave machines running unattended for
long periods of time (even though we've heard all the arguments in
favor of it). So the "every 11 minutes" feature becomes a bug.
</para>
<para>
This "feature/bug" appears to behave differently in different versions
of the kernel (and possibly in different versions of xntpd and ntpd as
well), so if you're running both ntpd and hwclock you may need to test
your system to see what it actually does. If you can't keep the kernel
from resetting the RTC, you might have to run without a correction
factor on the RTC.
</para>
<para>
The part of the kernel that controls this can be found in
/usr/src/linux-2.0.34/arch/i386/kernel/time.c (where the version
number in the path will be the version of the kernel you're running).
If the variable time_status is set to TIME_OK then the kernel will
write the system time to the RTC every 11 minutes, otherwise it leaves
the RTC alone. Calls to adjtimex(2) (as used by ntpd and timed, for
example) may turn this on. Calls to settimeofday(2) will set
time_status to TIME_UNSYNC, which tells the kernel not to adjust the
RTC. I have not found any real documentation on this.
</para>
<para>
I've heard reports that some versions of the kernel may have problems
with "sleep modes" that shut down the CPU to save energy. The best
solution is to keep your kernel up to date, and refer any problems to
the people who maintain the kernel.
</para>
<para>
If you get bizarre results from the RTC you may have a hardware
problem. Some RTC chips include a lithium battery that can run down,
and some motherboards have an option for an external battery (be sure
the jumper is set correctly). The same battery maintains the CMOS RAM,
but the clock takes more power and is likely to fail first. Bizarre
results from the system clock may mean there is a problem with
interrupts.
</para>
2.3. Should the RTC use Local Time or UTC, and What About DST?
<para>
The Linux "system clock" actually just counts the number of seconds
past Jan 1, 1970, and is always in UTC (or GMT, which is technically
different but close enough that casual users tend to use both terms
interchangeably). UTC does not change as DST comes and goes-- what
changes is the conversion between UTC and local time. The translation
to local time is done by library functions that are linked into the
application programs.
</para>
<para>
This has two consequences: First, any application that needs to know
the local time also needs to know what time zone you're in, and
whether DST is in effect or not (see the next section for more on time
zones). Second, there is no provision in the kernel to change either
the system clock or the RTC as DST comes and goes, because UTC doesn't
change. Therefore, machines that only run Linux should have the RTC
set to UTC, not local time.
</para>
<para>
However, many people run dual-boot systems with other OS's that expect
the RTC to contain the local time, so hwclock needs to know whether
your RTC is in local time or UTC, which it then converts to seconds
past Jan 1, 1970 (UTC). This still does not provide for seasonal
changes to the RTC, so the change must be made by the other OS (this
is the one exception to the rule against letting more than one program
change the time in the RTC).
</para>
<para>
Unfortunately, there are no flags in the RTC or the CMOS RAM to
indicate standard time vs DST, so each OS stores this information
someplace where the other OS's can't find it. This means that hwclock
must assume that the RTC always contains the correct local time, even
if the other OS has not been run since the most recent seasonal time
change.
</para>
<para>
If Linux is running when the seasonal time change occurs, the system
clock is unaffected and applications will make the correct conversion.
But if linux has to be rebooted for any reason, the system clock will
be set to the time in the RTC, which will be off by one hour until the
other OS (usually Windows) has a chance to run.
</para>
<para>
There is no way around this, but Linux doesn't crash very often, so
the most likely reason to reboot on a dual-boot system is to run the
other OS anyway. But beware if you're one of those people who shuts
down Linux whenever you won't be using it for a while-- if you haven't
had a chance to run the other OS since the last time change, the RTC
will be off by an hour until you do.
</para>
<para>
Some other documents have stated that setting the RTC to UTC allows
Linux to take care of DST properly. This is not really wrong, but it
doesn't tell the whole story-- as long as you don't reboot, it does
not matter which time is in the RTC (or even if the RTC's battery
dies). Linux will maintain the correct time either way, until the next
reboot. In theory, if you only reboot once a year (which is not
unreasonable for Linux), DST could come and go and you'd never notice
that the RTC had been wrong for several months, because the system
clock would have stayed correct all along. But since you can't predict
when you'll want to reboot, it's better to have the RTC set to UTC if
you're not running another OS that requires local time.
</para>
<para>
The Dallas Semiconductor RTC chip (which is a drop-in replacement for
the Motorola chip used in the IBM AT and clones) actually has the
ability to do the DST conversion by itself, but this feature is not
used because the changeover dates are hard-wired into the chip and
can't be changed. Current versions change on the first Sunday in April
and the last Sunday in October, but earlier versions used different
dates (and obviously this doesn't work in countries that use other
dates). Also, the RTC is often integrated into the motherboard's
"chipset" (rather than being a separate chip) and I don't know if they
all have this ability.
</para>
2.4. How Linux keeps Track of Time Zones
<para>
You probably set your time zone correctly when you installed Linux.
But if you have to change it for some reason, or if the local laws
regarding DST have changed (as they do frequently in some countries),
then you'll need to know how to change it. If your system time is off
by some exact number of hours, you may have a time zone problem (or a
DST problem).
</para>
<para>
Time zone and DST information is stored in /usr/share/zoneinfo (or
/usr/lib/zoneinfo on older systems). The local time zone is
determined by a symbolic link from /etc/localtime to one of these
files. The way to change your timezone is to change the link. If
your local DST dates have changed, you'll have to edit the file.
</para>
<para>
You can also use the TZ environment variable to change the current
time zone, which is handy of you're logged in remotely to a machine in
another time zone. Also see the man pages for tzset and tzfile.
This is nicely summarized at
<http://www.linuxsa.org.au/tips/time.html>
</para>
2.5. The Bottom Line
<para>
If you don't need sub-second accuracy, hwclock(8) and adjtimex(8) may
be all you need. It's easy to get enthused about time servers and
radio clocks and so on, but I ran the old clock(8) program for years
with excellent results. On the other hand, if you have several
machines on a LAN it can be handy (and sometimes essential) to have
them automatically sync their clocks to each other. And the other
stuff can be fun to play with even if you don't really need it.
</para>
<para>
On machines that only run Linux, set the RTC to UTC (or GMT). On
dual-boot systems that require local time in the RTC, be aware that if
you have to reboot Linux after the seasonal time change, the clock may
be temporarily off by one hour, until you have a chance to run the
other OS. If you run more than two OS's, be sure only one of them is
trying to adjust for DST.
</para>
<para>
NTP is a standard method of synchronising time on a client from a remote
server across the network. NTP clients are typically installed on servers.
NTP is a standard method of synchronising time across a network of
computers. NTP clients are typically installed on servers.
Most business class ISPs provide NTP servers. Otherwise, there are a
number of free NTP servers in Australia:
</para>
<para>
The Univeristy of Melbourne ntp.cs.mu.oz.au
University of Adelaide ntp.saard.net
CSIRO Marine Labs, Tasmania ntp.ml.csiro.au
CSIRO National Measurements Laboratory, Sydney ntp.syd.dms.csiro.au
</para>
<para>
Xntpd (NTPv3) has been replaced by ntpd (NTPv4); the earlier version
is no longer being maintained.
</para>
</para>
Ntpd is the standard program for synchronizing clocks across a
network, and it comes with a list of public time servers you can
connect to. It can be a little more complicated to set up, but if
you're interested in this kind of thing I highly recommend that you
take a look at it.
</para>
<para>
The "home base" for information on ntpd is the NTP website at
<http://www.eecis.udel.edu/~ntp/> which also includes links to all
kinds of interesting time-related stuff (including software for other
OS's). Some linux distributions include ntpd on the CD. There is a
list of public time servers at
<http://www.eecis.udel.edu/~mills/ntp/clock2.html>.
</para>
<para>
A relatively new feature in ntpd is a "burst mode" which is designed
for machines that have only intermittent dial-up access to the
internet.
</para>
<para>
Ntpd includes drivers for quite a few radio clocks (although some
appear to be better supported than others). Most radio clocks are
designed for commercial use and cost thousands of dollars, but there
are some cheaper alternatives (discussed in later sections). In the
past most were WWV or WWVB receivers, but now most of them seem to be
GPS receivers. NIST has a PDF file that lists manufacturers of radio
clocks on their website at
<http://www.boulder.nist.gov/timefreq/links.htm> (near the bottom of
the page). The NTP website also includes many links to manufacturers
of radio clocks at <http://www.eecis.udel.edu/~ntp/hardware.htm> and
<http://www.eecis.udel.edu/~mills/ntp/refclock.htm>. Either list may
or may not be up to date at any given time :-). The list of drivers
for ntpd is at
<http://www.eecis.udel.edu/~ntp/ntp_spool/html/refclock.htm>.
</para>
<para>
Ntpd also includes drivers for several dial-up time services. These
are all long-distance (toll) calls, so be sure to calculate the effect
on your phone bill before using them.
</para>
3.4. Chrony
<para>
Xntpd was originally written for machines that have a full-time
connection to a network time server or radio clock. In theory it can
also be used with machines that are only connected intermittently, but
Richard Curnow couldn't get it to work the way he wanted it to, so he
wrote "chrony" as an alternative for those of us who only have network
access when we're dialed in to an ISP (this is the same problem that
ntpd's new "burst mode" was designed to solve). The current version
of chrony includes drift correction for the RTC, for machines that are
turned off for long periods of time.
</para>
<para>
You can get more information from Richard Curnow's website at
<http://www.rrbcurnow.freeuk.com/chrony> or <http://go.to/chrony>.
There are also two chrony mailing lists, one for announcements and one
for discussion by users. For information send email to chrony-users-
subscribe@egroups.com or chrony-announce-subscribe@egroups.com
</para>
<para>
Chrony is normally distributed as source code only, but Debian has
been including a binary in their "unstable" collection. The source
file is also available at the usual Linux archive sites.
</para>
3.5. Clockspeed
<para>
Another option is the clockspeed program by DJ Bernstein. It gets the
time from a network time server and simply resets the system clock
every three seconds. It can also be used to synchronize several
machines on a LAN.
</para>
<para>
I've sometimes had trouble reaching his website at
<http://Cr.yp.to/clockspeed.html>, so if you get a DNS error try again
on another day. I'll try to update this section if I get some better
information.
</para>
<para>
Note
You must be logged in as "root" to run any program that affects
the RTC or the system time, which includes most of the programs
described here. If you normally use a graphical interface for
everything, you may also need to learn some basic unix shell
commands.
</para>
<para>
Note
If you run more than one OS on your machine, you should only let
one of them set the RTC, so they don't confuse each other. The
exception is the twice-a-year adjustment for Daylight Saving(s)
Time.
</para>
<para>
If you run a dual-boot system that spends a lot of time running
Windows, you may want to check out some of the clock software
available for that OS instead. Follow the links on the NTP website at
<http://www.eecis.udel.edu/~ntp/software.html>.
</para>
</sect1>

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@ -3310,3 +3310,85 @@ and up-to-date IPv6 implementation.
-----------------------------------------------------------------------------
</sect1 id="IPv6">
<sect1 id="STRIP">
<title>STRIP</title>
<para>
STRIP (Starnode Radio IP) is a protocol designed specifically for
a range of Metricom radio modems for a research project being
conducted by Stanford University called the MosquitoNet Project.
There is a lot of interesting reading here, even if you aren't
directly interested in the project.
</para>
<para>
The Metricom radios connect to a serial port, employ spread spectrum
technology and are typically capable of about 100kbps. Information on
the Metricom radios is available from the: Metricom Web Server.
</para>
<para>
At present the standard network tools and utilities do not support the
STRIP driver, so you will have to download some customized tools from
the MosquitoNet web server. Details on what software you need is
available at the: MosquitoNet STRIP Page.
</para>
<para>
A summary of configuration is that you use a modified slattach program
to set the line discipline of a serial tty device to STRIP and then
configure the resulting `st[0-9]' device as you would for ethernet
with one important exception, for technical reasons STRIP does not
support the ARP protocol, so you must manually configure the ARP
entries for each of the hosts on your subnet. This shouldn't prove too
onerous. STRIP device names are `st0', `st1', etc.... The relevant
kernel compilation options are given below.
</para>
<para>
<screen>
Kernel Compile Options:
Network device support --->
[*] Network device support
....
[*] Radio network interfaces
< > STRIP (Metricom starmode radio IP)
</screen>
</para>
</sect1 id="STRIP">
<sect1 id="WaveLAN">
<title>WaveLAN</title>
<para>
The WaveLAN card is a spread spectrum wireless lan card. The card
looks very like an ethernet card in practice and is configured in much
the same way.
</para>
<para>
You can get information on the Wavelan card from wavelan.com.
</para>
<para>
Wavelan device names are `eth0', `eth1', etc.
<para>
<screen>
Kernel Compile Options:
Network device support --->
[*] Network device support
....
[*] Radio network interfaces
....
<*> WaveLAN support
</screen>
</para>
</sect1 id="WaveLAN">

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<sect1 id="SSH">
<title>SSH</title>
<para>
The Secure Shell, or SSH, provides a way of running command line and
graphical applications, and transferring files, over an encrypted
connection. SSH uses up to 2,048-bit encryption with a variety of
cryptographic schemes to make sure that if a cracker intercepts your
connection, all they can see is useless gibberish. It is both a
protocol and a suite of small command line applications which can be
used for various functions.
</para>
<para>
SSH replaces the old Telnet application, and can be used for secure
remote administration of machines across the Internet. However, it
has more features.
</para>
<para>
SSH increases the ease of running applications remotely by setting up
permissions automatically. If you can log into a machine, it allows you
to run a graphical application on it, unlike Telnet, which requires users
to type lots of geeky xhost and xauth commands. SSH also has inbuild
compression, which allows your graphic applications to run much faster
over the network.
</para>
<para>
SCP (Secure Copy) and SFTP (Secure FTP) allow transfer of files over the
remote link, either via SSH's own command line utilities or graphical tools
like Gnome's GFTP. Like Telnet, SSH is cross-platform. You can find SSH
servers and clients for Linux, Unix, all flavours of Windows, BeOS, PalmOS,
Java and Embedded OSes used in routers.
</para>
<para>
Encrypted remote shell sessions are available through SSH
(http://www.ssh.fi/sshprotocols2/index.html
<http://www.ssh.fi/sshprotocols2/index.html>) thus effectively
allowing secure remote administration.
</para>
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<sect1 id="STRIP">
<title>STRIP</title>
<para>
STRIP (Starnode Radio IP) is a protocol designed specifically for
a range of Metricom radio modems for a research project being
conducted by Stanford University called the MosquitoNet Project.
There is a lot of interesting reading here, even if you aren't
directly interested in the project.
</para>
<para>
The Metricom radios connect to a serial port, employ spread spectrum
technology and are typically capable of about 100kbps. Information on
the Metricom radios is available from the: Metricom Web Server.
</para>
<para>
At present the standard network tools and utilities do not support the
STRIP driver, so you will have to download some customized tools from
the MosquitoNet web server. Details on what software you need is
available at the: MosquitoNet STRIP Page.
</para>
<para>
A summary of configuration is that you use a modified slattach program
to set the line discipline of a serial tty device to STRIP and then
configure the resulting `st[0-9]' device as you would for ethernet
with one important exception, for technical reasons STRIP does not
support the ARP protocol, so you must manually configure the ARP
entries for each of the hosts on your subnet. This shouldn't prove too
onerous. STRIP device names are `st0', `st1', etc.... The relevant
kernel compilation options are given below.
</para>
<para>
<screen>
Kernel Compile Options:
Network device support --->
[*] Network device support
....
[*] Radio network interfaces
< > STRIP (Metricom starmode radio IP)
</screen>
</para>
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<sect1 id="Samba">
8.11. SAMBA - `NetBEUI', `NetBios', `CIFS' support.
SAMBA is an implementation of the Session Management Block protocol.
Samba allows Microsoft and other systems to mount and use your disks
and printers.
SAMBA and its configuration are covered in detail in the SMB-HOWTO.
5.2. Windows Environment
Samba is a suite of applications that allow most Unices (and in
particular Linux) to integrate into a Microsoft network both as a
client and a server. Acting as a server it allows Windows 95, Windows
for Workgroups, DOS and Windows NT clients to access Linux files and
printing services. It can completely replace Windows NT for file and
printing services, including the automatic downloading of printer
drivers to clients. Acting as a client allows the Linux workstation to
mount locally exported windows file shares.
According to the SAMBA Meta-FAQ:
"Many users report that compared to other SMB implementations Samba is more stable,
faster, and compatible with more clients. Administrators of some large installations say
that Samba is the only SMB server available which will scale to many tens of thousands
of users without crashing"
· Samba project home page <http://samba.anu.edu.au/samba/>
· SMB HOWTO <http://metalab.unc.edu/mdw/HOWTO/SMB-HOWTO.html>
· Printing HOWTO <http://metalab.unc.edu/mdw/HOWTO/Printing-
HOWTO.html>
<glossentry>
<glossterm>
samba
</glossterm>
<glossdef>
<para>
A LanManager like file and printer server for Unix. The Samba software suite is a collection of programs that implements the SMB protocol for unix systems, allowing you to serve files and printers to Windows, NT, OS/2 and DOS clients. This protocol is sometimes also referred to as the LanManager or NetBIOS protocol. This package contains all the components necessary to turn your Debian GNU/Linux box into a powerful file and printer server. Currently, the Samba Debian packages consist of the following: samba - A LanManager like file and printer server for Unix. samba-common - Samba common files used by both the server and the client. smbclient - A LanManager like simple client for Unix. swat - Samba Web Administration Tool samba-doc - Samba documentation. smbfs - Mount and umount commands for the smbfs (kernels 2.0.x and above). libpam-smbpass - pluggable authentication module for SMB password database libsmbclient - Shared library that allows applications to talk to SMB servers libsmbclient-dev - libsmbclient shared libraries winbind: Service to resolve user and group information from Windows NT servers It is possible to install a subset of these packages depending on your particular needs. For example, to access other SMB servers you should only need the smbclient and samba-common packages. From Debian 3.0r0 APT
<ulink url="http://www.tldp.org/LDP/Linux-Dictionary/html/index.html">http://www.tldp.org/LDP/Linux-Dictionary/html/index.html</ulink>
</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>
Samba
</glossterm>
<glossdef>
<para>
A lot of emphasis has been placed on peaceful coexistence between UNIX and Windows. Unfortunately, the two systems come from very different cultures and they have difficulty getting along without mediation. ...and that, of course, is Samba&apos;s job. Samba &lt;http://samba.org/&gt; runs on UNIX platforms, but speaks to Windows clients like a native. It allows a UNIX system to move into a Windows ``Network Neighborhood&apos;&apos; without causing a stir. Windows users can happily access file and print services without knowing or caring that those services are being offered by a UNIX host. All of this is managed through a protocol suite which is currently known as the ``Common Internet File System,&apos;&apos; or CIFS &lt;http://www.cifs.com&gt;. This name was introduced by Microsoft, and provides some insight into their hopes for the future. At the heart of CIFS is the latest incarnation of the Server Message Block (SMB) protocol, which has a long and tedious history. Samba is an open source CIFS implementation, and is available for free from the http://samba.org/ mirror sites. Samba and Windows are not the only ones to provide CIFS networking. OS/2 supports SMB file and print sharing, and there are commercial CIFS products for Macintosh and other platforms (including several others for UNIX). Samba has been ported to a variety of non-UNIX operating systems, including VMS, AmigaOS, and NetWare. CIFS is also supported on dedicated file server platforms from a variety of vendors. In other words, this stuff is all over the place. From Rute-Users-Guide
<ulink url="http://www.tldp.org/LDP/Linux-Dictionary/html/index.html">http://www.tldp.org/LDP/Linux-Dictionary/html/index.html</ulink>
</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>
Samba
</glossterm>
<glossdef>
<para>
Samba adds Windows-networking support to UNIX. Whereas NFS is the most popular protocol for sharing files among UNIX machines, SMB is the most popular protocol for sharing files among Windows machines. The Samba package adds the ability for UNIX systems to interact with Windows systems. Key point: The Samba package comprises the following: smbd The Samba service allowing other machines (often Windows) to read files from a UNIX machine. nmbd Provides support for NetBIOS. Logically, the SMB protocol is layered on top of NetBIOS, which is in turn layered on top of TCP/IP. smbmount An extension to the mount program that allows a UNIX machine to connect to another machine implicitly. Files can be accessed as if they were located on the local machines. smbclient Allows files to be access through SMB in an explicity manner. This is a command-line tool much like the FTP tool that allows files to be copied. Unlike smbmount, files cannot be accessed as if they were local. smb.conf The configuration file for Samba. From Hacking-Lexicon
<ulink url="http://www.tldp.org/LDP/Linux-Dictionary/html/index.html">http://www.tldp.org/LDP/Linux-Dictionary/html/index.html</ulink>
</para>
</glossdef>
</glossentry>
Samba Authenticated Gateway HOWTO
Ricardo Alexandre Mattar
v1.2, 2004-05-21
</sect1>

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<sect1 id="TFTP">
<title>TFTP</title>
<para>
Trivial File Transfer Protocol TFTP is a bare-bones protocol used by
devices that boot from the network. It is runs on top of UDP, so it
doesn&apos;t require a real TCP/IP stack. Misunderstanding: Many people
describe TFTP as simply a trivial version of FTP without authentication.
This misses the point. The purpose of TFTP is not to reduce the complexity
of file transfer, but to reduce the complexity of the underlying TCP/IP
stack so that it can fit inside boot ROMs. Key point: TFTP is almost
always used with BOOTP. BOOTP first configures the device, then TFTP
transfers the boot image named by BOOTP which is then used to boot the
device. Key point: Many systems come with unnecessary TFTP servers. Many
TFTP servers have bugs, like the backtracking problem or buffer overflows.
As a consequence, many systems can be exploited with TFTP even though
virtually nobody really uses it. Key point: A TFTP file transfer client
is built into many operating systems (UNIX, Windows, etc....). These clients
are often used to download rootkits when being broken into. Therefore,
removing the TFTP client should be part of your hardening procedure.
For further details on the TFTP protocol please see RFC's 1350, 1782,
1783, 1784, and 1785.
</para>
<para>
Most likely, you'll interface with the TFTP protocol using the TFTP command
line client, 'tftp', which allows users to transfer files to and from a
remote machine. The remote host may be specified on the command line, in
which case tftp uses host as the default host for future transfers.
</para>
<para>
Setting up TFTP is almost as easy as DHCP.
First install from the rpm package:
<screen>
# rpm -ihv tftp-server-*.rpm
</screen>
</para>
<para>
Create a directory for the files:
<screen>
# mkdir /tftpboot
# chown nobody:nobody /tftpboot
</screen>
</para>
<para>
The directory /tftpboot is owned by user nobody, because this is the default
user id set up by tftpd to access the files. Edit the file /etc/xinetd.d/tftp
to look like the following:
</para>
<para>
<screen>
service tftp
{
socket_type = dgram
protocol = udp
wait = yes
user = root
server = /usr/sbin/in.tftpd
server_args = -c -s /tftpboot
disable = no
per_source = 11
cps = 100 2
}
</screen>
</para>
<para>
The changes from the default file are the parameter disable = no (to enable
the service) and the server argument -c. This argument allows for the
creation of files, which is necessary if you want to save boot or disk
images. You may want to make TFTP read only in normal operation.
</para>
<para>
Then reload xinetd:
<screen>
/etc/rc.d/init.d/xinetd reload
</screen>
</para>
<para>
You can use the tftp command, available from the tftp (client) rpm package,
to test the server. At the tftp prompt, you can issue the commands put and
get.
</para>
</sect1>

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<sect1 id="Telnet">
<title>Telnet</title>
<para>
Created in the early 1970s, Telnet provides a method of running command
line applications on a remote computer as if that person were actually at
the remote site. Telnet is one of the most powerful tools for Unix, allowing
for true remote administration. It is also an interesting program from the
point of view of users, because it allows remote access to all their files
and programs from anywhere in the Internet. Combined with an X server (as
well as some rather arcane manipluation of authentication 'cookies' and
'DISPLAY' environment variables), there is no difference (apart from the
delay) between being at the console or on the other side of the planet.
However, since the 'telnet' protocol sends data 'en-clair' and there are
now more efficient protocols with features such as built-in
compression and 'tunneling' which allows for greater ease of usage of graphical
applications across the network as well as more secure connections it is an
effectively a dead protocol. Like the 'r' (such as rlogin and rsh) related
protocols it is still used though, within internal networks for the reasons
of ease of installation and use as well as backwards compatibility and also
as a means by which to configure networking devices such as routers
and firewalls.
</para>
<para>
Please consult RFC 854 for further details behind its implementation.
</para>
<para>
· Telnet related software
<http://metalab.unc.edu/pub/Linux/system/network/telnet/>
</para>
</sect1>

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<sect1 id="VNC">
<title>VNC</title>
8.13. Tunnelling, mobile IP and virtual private networks
The Linux kernel allows the tunnelling (encapsulation) of protocols.
It can do IPX tunnelling through IP, allowing the connection of two
IPX networks through an IP only link. It can also do IP-IP tunnelling,
which it is essential for mobile IP support, multicast support and
amateur radio. (see
http://metalab.unc.edu/mdw/HOWTO/NET3-4-HOWTO-6.html#ss6.8)
Mobile IP specifies enhancements that allow transparent routing of IP
datagrams to mobile nodes in the Internet. Each mobile node is always
identified by its home address, regardless of its current point of
attachment to the Internet. While situated away from its home, a
mobile node is also associated with a care-of address, which provides
information about its current point of attachment to the Internet.
The protocol provides for registering the care-of address with a home
agent. The home agent sends datagrams destined for the mobile node
through a tunnel to the care-of address. After arriving at the end of
the tunnel, each datagram is then delivered to the mobile node.
Point-to-Point Tunneling Protocol (PPTP) is a networking technology
that allows the use of the Internet as a secure virtual private
network (VPN). PPTP is integrated with the Remote Access Services
(RAS) server which is built into Windows NT Server. With PPTP, users
can dial into a local ISP, or connect directly to the Internet, and
access their network as if they were at their desks. PPTP is a closed
protocol and its security has recently being compromised. It is highly
recomendable to use other Linux based alternatives, since they rely on
open standards which have been carefully examined and tested.
· A client implementation of the PPTP for Linux is available here
<http://www.pdos.lcs.mit.edu/~cananian/Projects/PPTP/>
· More on Linux PPTP can be found here
<http://bmrc.berkeley.edu/people/chaffee/linux_pptp.html>
Mobile IP:
· http://www.hpl.hp.com/personal/Jean_Tourrilhes/MobileIP/mip.html
· http://metalab.unc.edu/mdw/HOWTO/NET3-4-HOWTO-6.html#ss6.12
Virtual Private Networks related documents:
· http://metalab.unc.edu/mdw/HOWTO/mini/VPN.html
· http://sites.inka.de/sites/bigred/devel/cipe.html
7.4. VNC
VNC stands for Virtual Network Computing. It is, in essence, a remote
display system which allows one to view a computing 'desktop'
environment not only on the machine where it is running, but from
anywhere on the Internet and from a wide variety of machine
architectures. Both clients and servers exist for Linux as well as for
many other platforms. It is possible to execute MS-Word in a Windows
NT or 95 machine and have the output displayed in a Linux machine. The
opposite is also true; it is possible to execute an application in a
Linux machine and have the output displayed in any other Linux or
Windows machine. One of the available clients is a Java applet,
allowing the remote display to be run inside a web browser. Another
client is a port for Linux using the SVGAlib graphics library,
allowing 386s with as little as 4 MB of RAM to become fully functional
X-Terminals.
· VNC web site <http://www.orl.co.uk/vnc/>
<para>
Virtual Network Computing (VNC) allows a user to operate a session running on another machine.
Although Linux and all other Unix-like OSes already have this functionality built in, VNC
provides further advantages because it's cross-platform, running on Linux, BSD, Unix, Win32,
MacOS, and PalmOS. This makes it far more versatile.
For example, let's assume the machine that you are attempting to connect to is running Linux.
You can use VNC to access applications running on that other Linux desktop. You can also use
VNC to provide technical support to users on Window's based machines by taking control of
their desktops from the comfort of your server room. VNC is usually installed as seperate
packages for the client and server, typically named 'vnc' and 'vnc-server'.
VNC uses screen numbers to connect clients to servers. This is because Unix machines allow
multiple graphical sessions to be stated simultaneously (check this out by logging in to a
virtual terminal and typing startx -- :1).
For platforms (Windows, MacOS, Palm, etc) which don't have this capability, you'll connect
to 'screen 0' and take over the session of the existing user. For Unix systems, you'll need
to specify a higher number and receive a new desktop.
If you prefer the Windows-style approach where the VNC client takes over the currently
running display, you can use x0rfbserver - see the sidebox below.
VNC Servers and Clients
On Linux, the VNC server (which allows the machine to be used remotely) is actually
run as a replacement X server. To be able to start a VNC session to a machine, log
into it and run vncserver. You'll be prompted for a password - in future you can
change this password with the vncpasswd command. After you enter the password, you'll
be told the display number of the newly created machine.
It is possible to control a remote macine by using the vncviewer command. If it is
typed on its own it will prompt for a remote machine, or you can use:
vncviewer [host]:[screen-number]
> The VPN HOWTO, deprecated!!!!
> VPN HOWTO
> Linux VPN Masquerade HOWTO
</para>
10. References
10.1. Web Sites
Cipe Home Page <http://sites.inka.de/~bigred/devel/cipe.html>
Masq Home Page <http://ipmasq.cjb.net>
Samba Home Page <http://samba.anu.edu.au>
Linux HQ <http://www.linuxhq.com> ---great site for lots of linux
info
10.2. Documentation
cipe.info: info file included with cipe distribution
Firewall HOWTO, by Mark Grennan, markg@netplus.net
IP Masquerade mini-HOWTO,by Ambrose Au, ambrose@writeme.com
IPChains-Howto, by Paul Russell, Paul.Russell@rustcorp.com.au
</sect1>

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<sect1 id="WaveLAN">
<title>WaveLAN</title>
<para>
The WaveLAN card is a spread spectrum wireless lan card. The card
looks very like an ethernet card in practice and is configured in much
the same way.
</para>
<para>
You can get information on the Wavelan card from wavelan.com.
</para>
<para>
Wavelan device names are `eth0', `eth1', etc.
<para>
<screen>
Kernel Compile Options:
Network device support --->
[*] Network device support
....
[*] Radio network interfaces
....
<*> WaveLAN support
</screen>
</para>
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<sect1 id="Web-Serving">
<title>Web-Serving</title>
<para>
The World Wide Web provides a simple method of publishing and linking
information across the Internet, and is responsible for popularising
the Internet to its current level. In the simplest case, a Web client
(or browser), such as Netscape or Internet Explorer, connects with a
Web server using a simple request/response protocol called HTTP
(Hypertext Transfer Protocol), and requests HTML (Hypertext Markup
Language) pages, images, Flash and other objects.
</para>
<para>
In mode modern situations, the Web server can also geneate pages
dynamically based on information returned from the user. Either way
setting up your own Web server is extremely simple. There are many
choices for Web serving under Linux. Some servers are very mature,
such as Apache, and are perfect for small and large sites alike.
Other servers programmed to be light and fast, and to have only a
limited feature set to reduce complexity. A search on freshmeat.net
will reveal a multitude of servers.
</para>
<para>
Most Linux distributions include Apache <http://www.apache.org>.
Apache is the number one server on the internet according to
http://www.netcraft.co.uk/survey/ . More than a half of all internet
sites are running Apache or one of it derivatives. Apache's advantages
include its modular design, stability and speed. Given the appropriate
hardware and configuration it can support the highest loads: Yahoo,
Altavista, GeoCities, and Hotmail are based on customized versions of
this server.
</para>
<para>
Optional support for SSL (which enables secure transactions) is also
available at:
</para>
· http://www.apache-ssl.org/
· http://raven.covalent.net/
· http://www.c2.net/
Dynamic Web content generation
<para>
Web scripting languages are even more common on Linux than databases
- basically, every language is available. This includes CGI,
PHP 3 and 4, Perl, JSP, ASP (via closed source applications from
Chill!soft and Halycon Software) and ColdFusion.
</para>
<para>
PHP is an open source scripting language designed to churn out
dynamically produced Web content ranging from databases to browsers.
This inludes not only HTML, but also graphics, Macromedia Flash and
XML-based information. The latest versions of PHP provide impressive
speed improvements, install easily from packages and can be set up
quickly. PHP is the most popular Apache module and is used by over
two million sites, including Amazon.com, US telco giant Sprint,
Xoom Networks and Lycos. And unlike most other server side scripting
languages, developers (or those that employ them) can add their own
functions into the source to improve it. Supported databases include
those in the Database serving section and most ODBC compliant
databases. The language itself borrows its structure from Perl and C.
</para>
· http://metalab.unc.edu/mdw/HOWTO/WWW-HOWTO.html
· http://metalab.unc.edu/mdw/HOWTO/Virtual-Services-HOWTO.html
· http://metalab.unc.edu/mdw/HOWTO/Intranet-Server-HOWTO.html
· Web servers for Linux
<http://www.linuxlinks.com/Software/Internet/WebServers/>
</sect1>

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<sect1 id="X11">
<title>X11</title>
<para>
The X Window System was developed at MIT in the late 1980s, rapidly
becoming the industry standard windowing system for Unix graphics
workstations. The software is freely available, very versatile, and is
suitable for a wide range of hardware platforms. Any X environment
consists of two distinct parts, the X server and one or more X
clients. It is important to realise the distinction between the server
and the client. The server controls the display directly and is
responsible for all input/output via the keyboard, mouse or display.
The clients, on the other hand, do not access the screen directly -
they communicate with the server, which handles all input and output.
It is the clients which do the "real" computing work - running
applications or whatever. The clients communicate with the server,
causing the server to open one or more windows to handle input and
output for that client.
</para>
<para>
In short, the X Window System allows a user to log in into a remote
machine, execute a process (for example, open a web browser) and have
the output displayed on his own machine. Because the process is
actually being executed on the remote system, very little CPU power is
needed in the local one. Indeed, computers exist whose primary purpose
is to act as pure X servers. Such systems are called X terminals.
</para>
<para>
A free port of the X Window System exists for Linux and can be found
at: Xfree <http://www.xfree86.org/>. It is included in most Linux
distributions.
<para>
<para>
For further information regarding X please see:
</para>
X11, LBX, DXPC, NXServer, SSH, MAS
Related HOWTOs:
· Remote X Apps HOWTO
· Linux XDMCP HOWTO
· XDM and X Terminal mini-HOWTO
· The Linux XFree86 HOWTO
· ATI R200 + XFree86 4.x mini-HOWTO
· Second Mouse in X mini-HOWTO
· Linux Touch Screen HOWTO
· XFree86 Video Timings HOWTO
· Linux XFree-to-Xinside mini-HOWTO
· XFree Local Multi-User HOWTO
· Using Xinerama to MultiHead XFree86 V. 4.0+
· Connecting X Terminals to Linux Mini-HOWTO
· How to change the title of an xterm
· X Window System Architecture Overview HOWTO
· The X Window User HOWTO
</sect1>