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Linux tutorials
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Monitoring and Managing Linux Software RAID |
| Post date: April 15, 2005, 18:04 Category: System Views: 992 Comments: 0 |
Tutorial quote: Systems administrators managing a data center face numerous challenges to achieve required availability and uptime. Two of the main challenges are shrinking budgets (for hardware, software, and staffing) and short deadlines in which to deliver solutions. The Linux community has developed kernel support for software RAID (Redundant Array of Inexpensive Disks) to help meet those challenges. Software RAID, properly implemented, can eliminate system downtime caused by disk drive errors. The source code to the Linux kernel, the RAID modules, and the raidtools package are available at minimal cost under the GNU Public License. The interface is well documented and comprehensible to a moderately experienced Linux systems administrator.
In this article, I'll provide an overview of the software RAID implementation in the Linux 2.4.X kernel. I will describe the creation and activation of software RAID devices as well as the management of active RAID devices. Finally, I will discuss some procedures for recovering from a failed disk unit. |
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Linux 2.6: Compiling and Installing |
| Post date: April 15, 2005, 17:04 Category: System Views: 912 Comments: 0 |
Tutorial quote: We'll look at the process of compiling and installing a new kernel safely, without overwriting the existing kernel.
You can install as many kernels as you like on a Linux system, and select the one you want to run at boot time. This makes it easy to test different kernels, and different kernel configurations, with particular sets of hardware or applications. The wise network admin always tests new kernels before running them on production machines. |
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Building an LDAP Server on Linux, Part 2 |
| Post date: April 15, 2005, 12:04 Category: Network Views: 1111 Comments: 0 |
Tutorial quote: Welcome back! In Part 1 we learned basic concepts of LDAP and the uses for an LDAP server. Today we'll install and configure an OpenLDAP directory.
A quick note before we get started: this is LDAP 101. We are not installing any kind of encryption or strong authentication; we'll get to that in part 3. In my experience, learning LDAP in small chunks works best. (Then again, perhaps I'm just a bit dim.) So sit back, strap in, and keep your fingers away from the training wheels.
"The wise sysadmin will consult the documentation for their distro; it's quite possible that OpenLDAP will be packaged and ready to go in a pleasing manner (or ready to go in an odd manner--you never know). I'm all for easy--if your particular distribution provides an easy way, use it. RPMs can also be obtained from rpmfind.net, which thoughtfully lists all the required additional packages.
"Debian of course goes its own merry way. apt-get does the job just fine; the tricky bit is finding out the package names. Debian users want ldap-utils; slapd, which is OpenLDAP; and libdb4.1, to get the Sleepycat DB. These three components are enough to get you up and running. apt-get will walk you through a minimal configuration and will automatically start up slapd, the LDAP server daemon. |
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Building an LDAP Server on Linux, Part 1 |
| Post date: April 15, 2005, 12:04 Category: Network Views: 883 Comments: 0 |
Tutorial quote: Your network is growing in size and complexity. It's taking on a life of its own, spreading and growing and absorbing everything in its path. You're tearing your hair out trying to keep track, and your users have somehow discovered your secret phone number and are pestering you with endless questions and demands--where do I find this; I don't want to keep track of a dozen different passwords; nothing works like it should.
Of several possible solutions, consider two: 1) find a new hiding place, or 2) implement an LDAP server. While finding a new hiding place might sound ideal, it's an option we're going to have to save for a future article. This series will instead explain what LDAP is good for, detail how to build an LDAP server, and cover what you can do with it. |
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The Serial Console |
| Post date: April 14, 2005, 08:04 Category: Hardware Views: 1126 Comments: 0 |
Tutorial quote: In these modern times, a hardworking admin might be tempted to turn her back on the Old Ways, and indulge in increasingly exotic methods of interfacing with servers: SSH over ethernet, USB, Firewire, wireless, infrared, KVM switches, VNC, VPN... next stop: direct neural implants.
There's one old timer that still has useful place in the admin's tool kit: the serial console. Sure, it's slow and funky. But there are times it can be a real lifesaver. When nothing else works, it's a direct pipeline into your system. It's simple and cheap. You don't need to install drivers or expansion cards, it's just there.
Administration via serial console is common in data centers. Just imagine the nightmare of trying to connect all those rack units to keyboards and displays. The cabling can be extended to a nice comfortable ops center (well, an ops center, anyway). (This Lantronix Console Manager is an example of the type of device used to administer these.)
There are a number of ways to make the physical connection. You can connect an external modem--the kind us old timers fondly refer to as "real" modems--and do remote administration via dialup. It couldn't be any simpler, just dial direct. Or grab a null modem cable, connect to a laptop or a nearby workstation, and you have an instant terminal. |
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Tuneups and Tweaks for the Better Spam-Trap |
| Post date: April 14, 2005, 08:04 Category: Network Views: 770 Comments: 0 |
| Tutorial quote: In parts 1 and 2 of our thrilling "Building an Anti-Virus/Anti-Spam Gateway" series, we covered the basic steps for setting up SpamAssassin and Clam Anti-virus with Postfix. This installment is devoted to testing and tweaking, and creating whitelists in Amavisd-new. Whitelists are essential when you set up any kind of spam filtering: It's the best way to make sure your wanted mail gets through. |
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Feed Your Virus Worries to a Clam |
| Post date: April 14, 2005, 08:04 Category: Network Views: 885 Comments: 0 |
| Tutorial quote: Last week, we looked at how to set up SpamAssassin with Postfix, as part of a lean, mean, spam-killing gateway machine. This week we'll add an anti-virus scanner to our bubbling brew. |
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SpamAssassin and Amavisd |
| Post date: April 14, 2005, 08:04 Category: Network Views: 828 Comments: 0 |
| Tutorial quote: The bad news is, it's SpamAssassin, not SpammerAssassin. The good news is it kills spam quite effectively, and fits nicely into an anti-spam, anti-virus gateway. This article, which shows how to use SpamAssassin with Postfix, is the first in a series on building an anti-spam and anti-virus gateway. This gateway works equally well for a single PC, or for a large network. |
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Sawing Linux Logs with Simple Tools |
| Post date: April 14, 2005, 07:04 Category: Security Views: 937 Comments: 0 |
Tutorial quote: So there you are with all of your Linux servers humming along happily. You have tested, tweaked, and configured until they are performing at their peak of perfection. Users are hardly whining at all. Life is good. You may relax and indulge in some nice, relaxing rounds of TuxKart. After all, you earned it.
Except for one little remaining chore: monitoring your log files. [insert horrible alarming music of your choice here.] You're conscientious, so you know you can't just ignore the logs until there's a problem, especially for public services like Web and mail. Somewhere up in the pointy-haired suites, they may even be plotting to require you to track and analyze all sorts of server statistics.
Not to worry, for there are many ways to implement data reduction, which is what log parsing is all about. You want to slice and dice your logs to present only the data you're interested in viewing. Unless you wish to devote your entire life to manually analyzing log files. Even if you only pay attention to logfiles when you're debugging a problem, having some tools to weed out the noise is helpful. |
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Prep for Tomorrow with an IPv6 Testbed |
| Post date: April 14, 2005, 07:04 Category: Network Views: 714 Comments: 0 |
| Tutorial quote: Yes, friends, I am afraid you do have to start paying attention to IPv6 (Internet Protocol version 6). It's on its way, it's inevitable, and us ace network admins must learn to use it. |
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