LINUX NEWS
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October 17, 2002 -- Issue #103TABLE OF CONTENTS
1) Sean’s Notes
2) Linux News
Linux.com To Match Microsoft Donations
Red Hat Linux 8.0 Tops Desktop Class
India Moving to Linux
A Look At Gentoo3) Linux Resources
How Many Disks Are Too Many for a Linux System?
Active Directory Tool... For Linux
Log Files for Analysis
Conserve Energy... With Linux
Basic Makefiles4) App o’ the Week
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1) Sean’s Notes
The past couple of weeks I’ve been going over mail. First it was the flow of mail over the Internet, from your mail client (MUA), to your Mail Transfer Agent (MTA), to the recipient’s mailbox, and then into his MUA. Last week looked at the configuration of the PostFix MTA, which leaves one thing, namely getting the mail from your spool onto your desktop.
Two protocols are helpful for doing this, the Post Office Protocol Version 3 (POP3), and the Interactive Mail Access Protocol Version 4 (IMAP4).
POP is the simpler of the two; though it can do a lot more, it’s often used to grab your whole mail spool and delete it from the server. ISPs love it–they store your mail until you pick it up and get it off their hands.
My favourite POP implementation comes courtesy of Qualcomm, and is called “qpopper”. You can grab the sources from:
ftp://ftp.qualcomm.com/eudora/servers/unix/popper/qpopper4.0.4.tar.gz
To install it, uncompress the tarball:
tar -xzf qpopper4.0.4.tar.gz
Change into the directory:
cd qpopper4.0.4
If you run “./configure –help”, you’ll see all the options that you can set in this versatile daemon. I’ve always used:
./configure –enable-specialauth –enable-servermode
--with-openssl \ --enable-spool-dir=/var/spool/mail
--enable-uw-kludge --enable-poppassdYikes, eh? Since the POP daemon was one that I always kept up with upgrades, I made an RPM out of it so it would always build the same. Assuming you’re using Red Hat, you can do the same, too. Jump on over to:
http://boards.cramsession.com/boards/vbm.asp?me1927
- Save the content to /usr/src/redhat/SPECS/qpopper.spec
- Move qpopper4.0.4.tar.gz to /usr/src/redhat/SOURCES
- Run “rpm -ba /usr/src/redhat/SPECS/qpopper.spec” as root
- Install the rpm from /usr/src/redhat/RPMS/i386
Probably the source of another article or two, but building software as an RPM lets you ensure that you have it under package management, and that you always build the software the same (try remembering which options you used a year later!). If 4.0.5 comes out, copy the tarball to SOURCES, bump the version number within qpopper.spec, rerun rpm -ba qpopper.spec, and rpm -U the resulting RPM. Wondering what version of popper you’re running? rpm -q qpopper
If you didn’t go the rpm route, you can run:
make
make install
after you’ve run ./configure to do much the same thing, but without the package management.
Though there are dozens of options you can pass to the daemon, you can get by without them. To activate qpopper, we have to tell inetd about it. If you haven’t caught any of my articles on inetd, its job is to listen for connections to the POP port (TCP 110), and then spawn off a qpopper process to handle it. Saves a lot of memory if there are few connections!
Users of the older inetd will want to add the following line to inetd.conf:
pop3 stream tcp nowait root /usr/sbin/tcpd popper
If you’re using the newer xinetd, create /etc/xinetd.d/popper with the following:
service pop3 { flags = REUSE socket_type = stream wait = no user = root server = /usr/sbin/popper log_on_failure += USERID disable = no }
Either way, it tells inetd to listen on the pop3 port, and to run /usr/sbin/popper when it sees it, that is, once you restart inetd! They’ll both respect wrappers, which we’ll use to prevent everyone on the Internet from connecting to the POP daemon:
/etc/hosts.deny: popper: ALL
/etc/hosts.allow: popper: localhost, 192.168.1.
(I’m making the assumption here that your internal network is 192.168.1.0/24, change the line as appropriate if I was wrong.)
If you want to learn more about controlling access with hosts.allow and hosts.deny, “man 5 hosts_access” is for you. xinetd users get additional control with the man page for “xinetd.conf”.
So, we’ve built and installed a POP daemon. Inetd is set up to listen for POP requests, and has been restarted. Access control? Check. I guess we’re ready to try it out!
telnet localhost pop3
Trying 127.0.0.1… Connected to localhost. Escape character is ‘^]’. +OK Qpopper (version 4.0.4) at poochie starting. QUIT +OK Pop server at poochie signing off. Connection closed by foreign host.
(that was me typing QUIT, by the way).
Those interested in protocols might note that SMTP uses numeric codes for status, while POP uses either “+OK” or “-ERR”. So much for standards, eh?
If you got a “connection refused”, then it’s likely that something went wrong with the inetd setup. If it connects and kicks you out before giving a banner, then your ACLs are to blame.
At this point you’re ready to point your mail client to your brand new POP server. Have fun!
Though I’ll cover the second protocol, IMAP, in an upcoming newsletter, it is pretty much the same as what we did today. Some distributions even include the University of Washington version, which is the one I use myself. Install, enable in inetd, connect (port 143 this time).
Even if you’re not running your own domain at home, a POP server is handy if you want to read root’s email on another machine. Thus, you can get your logs on your desktop, without having to use a text-based email client.
Long live the Penguin,
Sean mailto:swalberg@cramsession.com
2) Linux News
Linux.com To Match Microsoft Donations
Microsoft has offered schools some free licences to their product, content that in a few years they’ll have paying customers. Linux.com has exactly the same offer, but with no strings! Take all the Linux you want! A very funny, but accurate, article.
http://newsforge.com/article.pl?sid/10/10/1511200
Red Hat Linux 8.0 Tops Desktop Class
eWeek took the new Red Hat 8 for a spin, and from the perspective of the desktop, was impressed. No screenshots, but still a good article.
http://www.eweek.com/article2/0,3959,633876,00.asp
India Moving to Linux
“INDIA’S GOVERNMENT Department of Information Technology has announced a sweeping initiative to move the entire country to Linux as its “platform of choice” in place of higher cost ‘proprietary’ software, reports the India Times subsidiary Economic Times.”
http://www.theinquirer.net/?articleW67
A Look At Gentoo
Gentoo Linux’s angle is that everything is compiled from source. I never realized some of the implications of this until I read this article. It definitely puts Gentoo on my “gotta try” list!
http://linux.oreillynet.com/pub/a/linux/2002/10/10/intro_gentoo.htm l
3) Linux Resources
How Many Disks Are Too Many for a Linux System?
Linux makes a great file server, but in many cases, the underlying computer imposes some restrictions on how much space you can cram into a single machine. Here’s an interesting look at disk capacities.
http://www.linuxjournal.com/article.php?sidb38
Active Directory Tool… For Linux
“adtool is a unix command line utility for Active Directory administration. Features include user and group creation, deletion, modification, password setting, and directory query and search capabilities.”
http://dexy.mine.nu/adtool/
Log Files for Analysis
Logs aren’t only for debugging, they’re a valuable forensic tool. This article from SecurityFocus goes over some ways to monitor your logs, and keep one step ahead of the Blackhats.
http://online.securityfocus.com/infocus/1633
Conserve Energy… With Linux
“AcquiSuite is a computerized device (manufactured by Obvius – Portland, OR) which is used for building automation and energy management. The device can lower the cost of operating a building by collecting and reporting information in a reliable, timely, and inexpensive manner.” And, it runs Linux!
http://www.linuxdevices.com/articles/AT9272306746.html
Basic Makefiles
Programmers use Makefiles to save recompiling code that’s already compiled, and to automate the process. It’s also a handy system administration tool. This article goes over what basic elements go in a Makefile.
http://www.linuxgazette.com/issue83/heriyanto.html
4) App o’ the Week
I’m always on the lookout for dynamic DNS providers, especially if they’re free. Here’s one I just found that fits the bill. Also great if you’ve been following along with the email discussions; with one of these dynamic names you can have a nicer domain name, and not have to fork out the cash for a .com.
http://www.staticcling.org/
(C) 2002 BrainBuzz.com, Inc. All Rights Reserved.
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