This description has been made to answer a few questions about how dial-up ISP (Internet Service Provider) subscribers may configure and use Linux.
To aid those who will connect their Linux based machines to an ISP for the first time, an attempt has been made to cover most issues encountered. This quite unavoidably will create a certain degree of overlap with other Linux Howto-documents and LDP books. Reference should be made to these documents to provide better understanding and detail.
Much of the existing documentation is targeted towards users with a certain degree of experience, and first time users will often have trouble sorting out the relevant information.
To simplify, the examples given will assume the following:
dirk will be calling his machine
All references in the table above should naturally be replaced by whatever is valid for the ISP one is using. Often, just a minimum of changes will otherwise be required for users with different ISPs. I would like to be informed about what problems you encounter on this account.
Copyright (c) 1996,1997,1998 by Egil Kvaleberg. This document may be distributed under the terms set forth in the LDP license at
No liability for the contents of this documents can be accepted. Use the concepts, examples and other content at your own risk.
One of many possible setups will be described. In the Linux world, there is usually a number of ways in which to accomplish things. Paragraphs containing hints to alternatives are marked by ALT: Please also note that FTP-references often will change slightly as new versions of programs arrive.
As far as I know, only programs that under certain terms may be used or evaluated for personal purposes will be described. Most of the programs will be available complete with source under GNU-like terms.
This document has been translated to the following languages:
German, by Cristoph Seibert:
Korean, by Kidong Lee:
French, by Eric Jacoboni:
Polish, by Piotr Pogorzelski: URL TBA
New versions of this document will be periodically posted to comp.os.linux.answers. They will also be added to the various anonymous FTP sites who archive such information, including:
In addition, you should generally be able to find this document on the Linux Documentation Project page via:
The very latest version of this document should also be available in various formats from:
All comments, error reports, additional information and criticism of all sorts should be directed to:
It will be assumed that we have installed the essential networking software modules from your Linux distribution, and that you have set up which serial port that is to be used for the /dev/modem.
The default configuration will usually only allow direct access
to /dev/modem as user
To connect to ISP shell accounts directly, and to experiment with connection sequences, you may use the minicom program. It is pretty straight forward to use.
Configuration of the machine for use on the net should be done as
root. Before proceeding any further, ensure that
/etc/hosts.deny contains the following line:
You would normally want to allow yourself, so add the following line to /etc/hosts.allow:
Or if you insist:
For the following, note that it is meant for those connected via PPP and with a dynamic IP address. If you have the benefit of a fixed connection, there will be some differences.
It is nice to have a name connected to the machine, a name that the dynamic IP user really can select as he or she pleases. Put the name in /etc/HOSTNAME:
The next step is to set up the name server in /etc/resolv.conf:
The name server must be specified by a numeric IP address, and will be different from ISP to ISP. If required, you can have up to three different servers, each on a separate line. They will be requested in the sequence in which they are listed.
search . nameserver 220.127.116.11 <nidx>nameserver
If you want to be able to use names like
an abbreviation for
somemachine.acme.xz, you must
replace the first line with:
A certain minimum of configuration will also be required in /etc/hosts. Most users will be able to manage with:
Those with a fixed IP-address will obviously replace 0.0.0.0 with that.
127.0.0.1 localhost 0.0.0.0 roderick
Likewise, a minimum /etc/networks is:
loopback 127.0.0.0 localnet 0.0.0.0
You should also set your external mail domain in /etc/mailname:
The username and password at the ISP must be specified in /etc/ppp/pap-secrets
dirk * PrettySecret
For those ISPs using CHAP instead of PAP the filename is /etc/ppp/chap-secrets.
Finally, the nitty gritty regarding the connection procedure itself must be specified before PPP can be initiated. This is done in /etc/ppp/chatscript:
Details here may have to be tuned somewhat. The phone number in the third line must of course be set as required. Some users may need to replace the
TIMEOUT 5 "" ATZ OK ATDT12345678 ABORT "NO CARRIER" ABORT BUSY ABORT "NO DIALTONE" ABORT WAITING TIMEOUT 45 CONNECT "" TIMEOUT 5 "name:" ppp
ATZmodem initialization string with something more tailored for the modem being used. The last line specifies that one is expecting a prompt that ends with
name:, and that the response should be
pppwhen it arrives. Other systems may have other login procedures.
To actually initiate a call, the PPP protocol may be initiated by issuing the following command:
We should now be on-air, and stay up until the program is killed by typing a ctrl-C. Any messages concerning the connection will be appended to the system logs. To read them, try:
exec pppd connect \ 'chat -v -f /etc/ppp/chatscript' \ -detach crtscts modem defaultroute \ user dirk \ /dev/modem 38400
As long as PPP is up, you will have direct access to the Internet and may use programs like ftp, ncftp, rlogin, telnet, finger etc. All these programs should be part of the network package.
Further information concerning PPP is also available from:
Finally, an additional word about security The file /etc/inetd.conf lists all services that your machine will offer externally. With the /etc/hosts.deny file we have made, no external access will be allowed. For those who need it, access must be allowed explicitly in /etc/hosts.allow. Local traffic may be allowed by:
man 5 hosts_access.
A final minor issue: A certain confusion exists regarding the names of the POP protocols. A definition in /etc/services compatible with just about everything is:
pop2 109/tcp pop-2 # PostOffice V.2 pop3 110/tcp pop-3 pop # PostOffice V.3
ALT: Instead of chatscript, one might use the much more flexible dip. But not in connection with diald.
ALT: Those fortunate enough to have a permanent TCP/IP connection via e.g. an Ethernet may safely ignore anything about PPP and rather start concentrating about setting up their network card.
ALT: Others may not have the possibility of using PPP, but may be able to use SLIP instead, for which there is support in much the same manner as for PPP. Another possibility is UUCP Others again may have to rely on exchange of news and email be means of SOUP A description for the latter case may be found in:
The TERM program is also an option. Refer to the Term-HOWTO.
If you think that text is the most important, you might want to use the Lynx web browser. It is available from:
If you have installed the X window system, you can also use one of the many graphical browsers. Chimera may be found at:
Netscape (aka. Mozilla
These browsers are constantly available in new and in various ways exciting versions.
Use and evaluation of these programs is subject to certain terms. Please observe them.
First of all, ensure that sendmail is installed. Sendmail sorts internal and out-bound mail, and will buffer out-bound mail until such time it is possible to forward it.
Sendmail is based on a configuration found in /etc/sendmail.cf. An example suitable for ISP users can be found in:
This is based on
procmail as a
delivery agent but may easily be changed to use
It is if course required to have an official domain address for out-bound mail, something which is specified in sendmail.cf:
This assumes that you have the same user name locally as you have at your ISP. If it is different, just specify the full name instead:
# who I masquerade as (null for no masquerading) DMacme.xz
Sendmail is now configured for sending directly to the recipient. To avoid long and repeated connections in those cases where the connection to the receiving end is slow and irregular, is is usually nice to use ones ISP as a buffer store. This can be specified by the DS specification:
Beware that sendmail is somewhat sensitive to handling of tab stop characters in sendmail.cf. You might want to use the vi editor to ensure that these tab characters are retained unchanged.
# "Smart" relay host (may be null) DSmail.acme.xz
Email reception can often be performed via the POP3 protocol, which can be initiated every time the connection is brought up. A script for testing this is:
This script may be started after PPP connection has been established. Beware that this script is just for testing, so ensure that the local mailbox is left untouched while it runs. The
sendmail -q popclient -3 -v mail.acme.xz -u dirk -p "PrettySecret" \ -k -o /usr/spool/mail/dirk
-koption means that the mail is kept in the ISP mailbox, and you are simply given a copy of the mail. You would of course want to remove this option once you are confident that your setup is working.
Beware that the password will show on the command line. Also note that popclient is getting old fashioned, and that you should consider using fetchmail instead.
A more secure and better version of this script may be found at:
This version of the script requires that procmail is installed, but that is something you'll never regret anyway. Most distributions include it, otherwise you may try:
Procmail is a simple and flexible tool that can sort incoming email based on a large range of criteria. In addition to being able to handle automated tasks like vacation messages and such.
Note that when we use procmail directly as in this case, the situation is somewhat different from what is described in the procmail documentation. A .forward is not required, and we also don't need a .procmailrc. The latter is only required if we want to sort the mail.
The user interface for reading and sending of email can be found in programs like pine or elm.
ALT: Fetchmail has recently become an improved alternative to popclient. The latest version is available from:
ALT: For an ordinary dial-up ISP user it is not really necessary to have the sendmail daemon active. To reduce resource usage, and possibly other problems, one may thus comment out any startup of sendmail, as is usually found in /etc/rc.d/rc.M (this varies from distribution to distribution).
ALT: In place of sendmail one might use the simpler smail. You'll find a good description of it (as well as most other things mentioned here) in the Linux Network Administrator's Guide.
ALT: There is also an m4 macro package for making a fresh /etc/sendmail.cf. For a simple installation it might be just as well to modify an existing configuration.
ALT: There are also simpler although less flexible alternatives for handling email. Pine may run stand-alone as long as it is configured properly, for instance. It might even be possible to use newer versions of some web-browsers.
ALT: Many are very enthusiastic regarding the Emacs companion Gnus as an email and news handler. Further information can be found at:
ALT: An alternative to popclient is pop-perl5. It is available from:
As long as PPP is active, it will be possible to read news online. There are lots of available programs, two simple alternatives being rtin and trn.
To start reading news, the only thing required in terms of configuration in most cases is to set NNTPSERVER (usually once and for all in the file .profile):
To get the From-address correct in postings, some programs may require:
To be able to read news while offline and thus reduce phone bills and give greater flexibility, one must set up a local news-spool of one sort or the other. This requires some configuration, and there will also be a certain amount of disk space involved. After initial setup, things should run more or less by themselves, with only some attention needed from time to time.
Two different solutions will be described here.
The solution described here is based on the news-server C News and the NNTP protocol. C News was originally targeted towards another sort of configuration, but is flexible enough to handle our situation too. One might also use the more recent INN news server but it might require a bit more in terms of resources. Either way, be careful not to install both; they don't live together easily.
It is crucial that all maintenance of news is done while logged
in as user
news, and that all configuration
files is placed in
/usr/lib/news. One way of handling this is, while
logged in as
root to write
The most important files in the configuration are:
addgroup comp.os.linux.networking y.
Dirk Gently's Holistic Detective Agency
sitein the Path: thread. In a setup as described here, using newsx, this name will never leave the machine, so you can set this to whatever you like as long as you are pretty sure it is unique. In this case
acme.xzto the Path, and that this is the only news source we have. The example given really tells that we will accept everything that arrives, and that we will only post news to
acme.xzthat it hasn't seen before, and is originally posted at our own site. In this simplified setup we assume that the all groups will come from a single source.
/allspecifies the distribution, and must be included. The letter
Fsays that (pointers to) outgoing news articles will be collected in a file.
C News needs a certain degree of daily maintenance, but this can
be specified once and for all via the command
issued as user
news. A suggested
setup follows; it can be tuned as required:
newsrun moves articles in and out (twice every hour), doexpire will delete articles as they get old (every night at 00:30), and the three last commands does various supervisory and error correcting tasks.
# maintain incoming and outgoing batches 10,40 * * * * /usr/lib/newsbin/input/newsrun # expire C News, once a day 30 0 * * * /usr/lib/newsbin/expire/doexpire # monitor and report if needed 00 2 * * sat /usr/lib/newsbin/maint/addmissing 40 3 * * * /usr/lib/newsbin/maint/newswatch 50 3 * * * /usr/lib/newsbin/maint/newsdaily
One should also ensure that things are cleaned up when starting the machine. As user root, add the following line to /etc/rc.d/rc.local:
News may be collected via the program NewsX, picking news from an NNTP-server The program can be found at:
su news -c /usr/lib/newsbin/maint/newsboot
NewsX is quite simple.
Installation is a classic case of:
make su make install exit
With the setup outlined here, all you have to do is to create the groups you want to read using the addgroup command.
To fetch articles, user
news issues the
following commands (assuming communication via PPP or similar is
newsrun newsx acme news.acme.xz newsrun
-d gives continuous printout to the screen.
Refer to the NewsX documentation for further information.
NewsX will also take care of posting of outgoing news.
To control disposal of articles as they get old, a file
explist is required. The comments in this
example should explain what we want to do:
# hold onto history lines 14 days, nobody gets >120 days /expired/ x 14 - /bounds/ x 0-1-120 - # retain these for 2 months comp.sources,comp.os.linux.all x 60 - # noise gets thrown away fast junk,control x 2 - # default: 14 days, no archive all x 14 -
ALT: In a small news-spool, one will usually not need
control. The traffic is huge
compared to the possible usefulness. The main point is that
articles will be canceled, and that groups may be created
automatically. To ensure that control messages containing
newgroup not shall mess up things for us, a file called
what we will allow:
In this example, all proper groups under comp.os.linux will be created (y), and the user
comp.os.linux firstname.lastname@example.org yv all any nq
newswill be notified (v). Everything else will be silently (q) ignored (n). The last line is sufficient if you want to create all groups manually.
ALT: An alternative to NewsX is suck.
A different solution altogether is to install the integrated package leafnode. This will handle all tasks required for a personal news spool, and is easy to configure. It is available via:
As for C News, all news maintenance really should be performed as
The home directory for leafnode is in /usr/lib/leafnode. To install, write:
cd /usr/lib/leafnode tar -xzvf leafnode-0.8.tgz cd leafnode-0.8 make su make install
Note in the following that the prefix /usr/local/sbin should be replaced with /usr/sbin if you installed leafnode from a package.
While still being logged in as
root, change the line
that controls NNTP in
Activate it by:
nntp stream tcp nowait news /usr/sbin/tcpd /usr/local/sbin/leafnode
killall -HUP inetd
Return to user
news by writing exit. In
/usr/lib/leafnode/config change the line that
defines the NNTP server. In our case:
server = news.acme.xz
Leafnode will look after itself by adding the following command
crontab -e as user
# expire Leafnode, once a day 0 4 * * * /usr/local/sbin/texpire
News exchange is also done as user
news by the following
command (assuming PPP is up and running):
Users who wants to read news should then use the recipe in How do I set up an online news-reader?, except that they configure for the local machine, i.e:
That should be all there is to it. The first
fetch will transfer a list of available
newsgroups. Leafnode will then monitor what groups the users are
requesting, and adapt to this the next time it is
Note that leafnode does not seems to work in cases where NNTP authorization is required. +.LP
ALT: An alternative to leafnode is nntpcache, available from:
ALT: Another alternative is to use the newsreader
slrn together with the
slrn-pull package. The newsreader must
be compiled with the
spool feature set.
Automated handling of news and email is quite easy to implement in Linux.
First and foremost one should make a /usr/lib/ppp/ppp-on that initiates the ISP connection. Often, this file will simply contain the following:
Further specification will be performed in /etc/ppp/options:
connect "/usr/lib/ppp/chat -v -f /etc/ppp/chatscript" crtscts modem defaultroute asyncmap 00000000 user dirk /dev/modem 38400
To end a connection, use the supplied version of /usr/lib/ppp/ppp-off.
Having tested the functionality of these two scripts, one must then write scripts that perform the various tasks. The script to collect email has been described before, and we will here assume it is located at /home/dirk/pop.
A script for exchange of email can then be produced in /root/mail:
#! /bin/sh # # exchange mail # 10 minutes timeout: TIMEOUT=600 DT=10 # kick sendmail: sendmail -q & # retrieve mail: su dirk -c /home/dirk/pop # wait for sendmail to terminate: t=0 while ! mailq | grep -q "Mail queue is empty"; do t=$[$t+$DT] if [ $t -gt $TIMEOUT ] ; then echo "sendmail -q timeout ($TIMEOUT).." exit 1 fi sleep $DT done exit 0
The script to exchange news may be placed in /usr/lib/news/news:
A script to connect the various bits and pieces remains, and can be placed in /root/news+mail:
#!/bin/sh # # exchange news # must be run as news: cd /usr/lib/news #update the outgoing batch (C News): /usr/lib/newsbin/input/newsrun < /dev/null #exchange news: /usr/lib/newsbin/newsx acme news.acme.xz #and flush the incoming batch: /usr/lib/newsbin/input/newsrun < /dev/null
#!/bin/sh # # exchange news and email # must be run as root # if ! /usr/lib/ppp/ppp-on; then exit 1 fi trap "/usr/lib/ppp/ppp-off" 1 2 3 15 #exchange news+mail: /root/mail & su news -c ~news/news wait #disconnect.. /usr/lib/ppp/ppp-off #update the incoming batch (C News): su news -c /usr/lib/newsbin/input/newsrun < /dev/null & exit 0
It is quite easy to make an extension to the above that only will establish a connection if outgoing email and news is present. Lets call it /root/news+mail.cond, and keep in mind that the name of the outgoing news-spool must be updated to suit:
#!/bin/sh # # exchange news and email, only if outgoing news or mail # (C News spool) if [ -s /var/spool/news/out.going/acme/togo ] || ! ( mailq | grep -q "Mail queue is empty"); then /root/news+mail fi
The only thing remaining is to specify when all this is going to
happen. This is done using the command
as root. Let us assume that we always want
to exchange news and mail at 07:00 in the morning, and after that
every 4th hour assuming there are outgoing email and news:
Ensure that every component is tested well before you connect them together. One may later add several other tasks, such as adjustment of the time of day (using ntpdate), and automatic update (mirroring) of locally maintained WWW and FTP files up to the ISP (using make and ftp).
00 7 * * * /root/news+mail 00 11,15,19,23 * * * /root/news+mail.cond
ALT: Depending on ones preferences, it is also possible
to turn the process upside down. Every time a PPP link is
initiated, the script
/etc/ppp/ip-up will be started. One may here add
whatever magic is required to start exchange of email and news.
man pppd for further detail.
ALT: It is also possible to automatically connect PPP whenever network traffic is detected. This is in many ways the more elegant solution, but it is quite dependent on a good configuration to avoid frequent (and costly) connections being made. More information can be found at:
diald utility is available from:
At the same location one will also find other variations on the theme PPP connections.
newaliasesevery time you change this. An example that should cover most eventualities is:
PostMaster: root ftp: root news: root usenet: root FaxMaster: root fax: root WebMaster: root MAILER.DAEMON: root
More specific information for certain ISPs is available from a variety of sources:
PowerTech, Telenor Online, Telia
AOL is not possible since AOL uses a proprietary protocol.
If you can supply ISP specific information not listed here, please get in touch.
The Linux Documentation Project book called Linux Network Administrator's Guide by Olaf Kirch is pretty mandatory for anyone that will set up and maintain anything involving TCP/IP and Internet
The documentation that follows each software package will normally give you all the detailed information you need, if not always the overview. The man-pages will be the first place to look. Try for instance:
You will also find some documentation about certain programs in the /usr/doc tree, although this is not always well structured.
The following HOWTOs will be highly relevant:
Red Hat has a mailing list for PPP issues; to join send an email to
with the subject line
Information here is collected from many sources. Thanks to the following that either indirectly or directly have contributed:
Adam Holt <email@example.com> Arne Coucheron <firstname.lastname@example.org> Arne Riiber <email@example.com> Arnt Gulbrandsen <firstname.lastname@example.org> Bjorn Steensrud <email@example.com> Gisle Hannemyr <firstname.lastname@example.org> Hans Amund Rosbach <email@example.com> Hans Peter Verne <firstname.lastname@example.org> Harald T Alvestrand <Harald.T.Alvestrand@uninett.no> Harald Terkelsen <Harald.Terkelsen@adm.hioslo.no> Haavard Engum <email@example.com> James Youngman <JYoungman@vggas.com> Johan S. Seland <firstname.lastname@example.org> John Phillips <email@example.com> Jorn Lokoy <firstname.lastname@example.org> Kenneth Tjostheim <email@example.com> Kjell M. Myksvoll <firstname.lastname@example.org> Kjetil T. Homme <email@example.com> Michael Meissner <firstname.lastname@example.org> N J Bailey <N.J.Bailey@leeds.ac.uk> Nicolai Langfeldt <email@example.com> Ove Ruben R Olsen <Ove.R.Olsen@ub.uib.no> R. Bardarson <firstname.lastname@example.org> Steinar Fremme <email@example.com> Sverre H. Huseby <firstname.lastname@example.org> Trond Eivind Glomsrod <email@example.com> Tommy Larsen <firstname.lastname@example.org> Yves Bellefeuille <email@example.com>