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Our experts answer your technical questions.

Tweaking inodes and Block Sizes

I want to ask a couple of questions. 1) I was wondering if there was a serious performance impact to formatting a Linux partition with the following commands:

mkfs.ext2 -i 1024 -b 1024 /dev/hda1
mkfs.ext3 -i -1024 -b 1024 /dev/hda2

I know that using the second command would enable the Journal filesystem, but would having so many inodes slow down the system? I'm trying to use this on a firewall system with Squid, INN and qmail services.

2) I have a matching pair of 486DX 66MHz systems and a 486SLC2 50MHz system, each with 32MB of RAM. Is there any way I could use Linux Rat Hat 9 on them? Or should I install Red Hat 6.2 and use up2date on them?


Lee Spivey


tuskyhe@yahoo.com

1) The effect of the size and number of inodes on disk access speed depends on the types of files they are used to reference. The commands given above indeed would yield greater utilization of the hard drive's capacity, and this seems like a good thing. This is especially true on larger hard drives, which multiply the effect of this value.

In practice, however, Web pages and messages have grown beyond 1KB files. Limiting a filesystem's block size to this value forces Linux to traverse a much larger tree of inodes to find the relevant entries and then remember which they are. The more inodes there are in one file, the longer this takes. Given the cost per megabyte of hard drives today, and the likelihood that the savings would amount to less than 100MB of space, 4–8KB might be a more reasonable value.


Chad Robinson


chad@lucubration.com

1) As Chad pointed out, the block size you choose will affect the performance. If the files you access the most often are over 1KB in size, you will have to access multiple inodes to retrieve these files and, thus, incur a performance hit. It's not so much a question of having a lot of inodes, but rather one of how many inodes will need to be accessed in order to retrieve the most commonly used files. That is, the issue is the average inode-to-file-size ratio—the inverse of the -i parameter in your mkfs command. Take this into consideration when laying out your filesystem and decide whether you want to optimize for speed or for total storage capacity. And, take into account what you predict to be the average size of what will be the most commonly accessed files. Also, make sure you don't limit yourself to too few inodes. It's likely that you will end up with significantly more files in the long run than you originally thought—depending on what you plan to do with the machine, of course—so make sure to not be too stingy. As for the performance issues between ext2 and ext3, an additional amount of overhead is associated with a journaling filesystem, but the performance hit generally is thought to be minimal, especially when weighed against the benefit of having a journal.


Timothy Hamlin


thamlin@nmt.edu

2) Neither Red Hat 9 nor Red Hat 6.2 is still supported, which means no more security updates. The successor, Fedora, requires a Pentium or better. You'll need to install a distribution such as Gentoo or Debian that has both pre-Pentium CPU support and current security fixes.

No matter what you install, this class of machine will be too slow for a modern desktop. You can use them for Web servers, print servers, firewalls or machines to learn on, though.


Don Marti


dmarti@ssc.com

Old Red Hat

I am having a problem with a Red Hat 7.2 installation on a 133MHz PC that I'm using as a Smoothwall proxy. I successfully installed the software, but when the computer rebooted and I tried to log in, I got a message similar to error in service mode. It's hard to tell because it flashes on the screen very quickly and then brings me back to a login screen. I checked the filesystem and made sure that bash was installed and that the environment path was set correctly. There still is something wrong though, because it's not logging me in. Can you suggest what the problem might be or, even better, point me toward a solution to this issue? I really would appreciate it.


Jeff


jloyd1@comcast.net

When the system is booted up and is showing the login screen, press and hold the Ctrl-Alt keys and press the F1 function key. This gives you the command line. You should be able to log in there as the root user with the root password. You can navigate to console 1 through 6 by using the Alt-F1 to Alt-F6 key combinations; F7 is graphical display. As you navigate from console 1 to 6, you may see more details about the error message and/or the events leading to it. Once you log in, look at /var/log/messages and other log files in the /var/log directory. This should get you started.


Usman S. Ansari


usmannsari@yahoo.com

Are you running with a graphical login? If so, try disabling it by editing /etc/inittab and changing to runlevel 3 instead of 5. Change the line:

x:5:respawn:/etc/X11/prefdm -nodaemon

to:

x:3:respawn:/etc/X11/prefdm -nodaemon

or do it temporarily through your bootloader. If you aren't running xdm, try examining your log files and searching for errors. Specifically, look at /var/log/messages and /var/log/secure, and if using X, look in the X logs as well.


Timothy Hamlin


thamlin@nmt.edu

Which Distribution?

This may be a silly question, but I'm considering putting Linux on my 80GB HD as a second OS. I'm looking to use it mainly for media, word processing, movies and music, as I've heard Linux is resource efficient. I'll be keeping Windows on mainly for gaming. I also have an Athlon 64 3500+ and want to make use of it with a 64-bit build that works well. Can you direct me to a distro that would allow me to use my 64-bit processor to its best ability and that also would allow for easy media playback, Net surfing and so on? I looked at MandrakeLinux, but I've been hearing a lot of bad things about its AMD64 build. Thanks for your time, and I look forward to hearing your response.


Derek Allen


sock_ferret@hotmail.com

If I may shamelessly plug Gentoo (www.gentoo.org), this distribution allows you to get the most out of almost any hardware platform, because you have the option of natively compiling packages for your platform as you install them. This feature also commonly is listed as Gentoo's downside, because this process can be time consuming. However, the Gentoo team has worked hard to provide binary builds for a variety of platforms, including 64-bit, so this is less of an issue today.

Gentoo's installation process can be daunting, and although the developers are working on a formal installer, you may or may not like what you see when you start to load it. If you need an alternative, Red Hat and Novell/SuSE are good places to start. Both provide native builds and clear, intuitive installers. For a free option, you can't go wrong with Debian, whose developers call their AMD64 port “the most complete port after i386”—clearly an in-demand platform. All of the distributions mentioned here provide package managers that allow you to keep your system up to date and easily install new applications, such as the media players and, more important, the codecs you are after.


Chad Robinson


chad@lucubration.com

Finding the Home Page

I am running Red Hat 9.0, kernel 2.4.20-8, and I am using the supplied Apache server. When I log on to the server, I see a Test Page. I have my home page files in /var/local/www/html, as instructed. I am told to swap the test page for my home page, which is what I want to do. Have you any idea what file I should edit to make this happen? I have printed out the 15 pages of the httpd.conf file and scanned them for more than a few days, to no avail.


George Robertson


grobertson29@earthlink.net

I believe in Red Hat 9's default Apache installation, the test page is located in /var/www/html/index.html. So if you want to replace it, back up that file and replace it with yours.


Timothy Hamlin


thamlin@nmt.edu

Look for the DocumentRoot line in your Apache configuration file. That's the directory where your home page lives. Now look for the DirectoryIndex line. That's a list of possible names for the file. Before you put too much work into the system, though, you'd be better off to upgrade to a distribution that has current security updates. Red Hat 9 security fixes ended on April 30, 2004.

Is this Red Hat Museum Week or something?


Don Marti


dmarti@ssc.com

Remote Administration

I have been administering Windows servers through a VPN connection for a long time. Is there a similar way to administer Linux systems? I realize I can VPN to a Linux system, but I mean is there a preferred method to access Linux systems remotely and do administration work? Could you recommend any books on the subject?


Ric Jones


rictjones@wideopenwest.com

The classic tool for administering Linux systems remotely is OpenSSH (www.openssh.com). It comes pre-installed on all the common distributions and gives you an encrypted way to run commands and transfer files without setting up a VPN. If you do want a VPN, Mick Bauer has an overview at /article/7881.


Don Marti


dmarti@ssc.com

Intranet DNS

I am trying to configure a bind server for my intranet using a residential cable modem router as the DHCP server. I am interested in having an intranet name to private IP address resolution and have any Internet DNS request forwarded to my ISP's DNS servers. I have been successful with getting the server to respond to an address record request (ls -t), but it won't return individual hostname IP addresses.

I have the root zone configured to point back to the bind server on the same PC. I also set up the domain zone ort.cloud containing the bind server host PC, router IP and hostnames of the individual network PC's IP to name mapping and canonical name to IP address mapping. Another zone takes care of the name to IP address and canonical name to IP address mapping. I'm not sure whether this redundancy is necessary or not, but it's kind of working for the time being.


Jeff


jloyd1@comcast.net

Probably the best source for information on setting up a DNS is the DNS-HOWTO, www.tldp.org/HOWTO/DNS-HOWTO.html. The author of that HOWTO, Nicolai Langfeldt, also has written a book entitled DNS and Bind that claims to offer more details and examples than the HOWTO. I have a setup similar to the one you are looking to achieve: an internal DNS that serves the local private domain requests and connects to an outside server for external translations. If I recall correctly—it's been a while since I set it up—I found numerous simple examples and configs for accomplishing what I needed by Googling for “caching only nameserver”.


Timothy Hamlin


thamlin@nmt.edu

Nonstandard Driver Breaks on New Kernel

For some time I hesitated to forward my problem to you, but I have no idea how to solve it. My distribution is Slackware 10.0, my kernel 2.6.9, the compiler 3.3.4, and I am booting from CD with isolinux. The problem is the modem chip 536EP from Intel is not supported under Linux. The Intel-provided source code, Intel-536ep-4.69-5.4.src.rpm, is okay and my modem works. When I use a new kernel, I have to compile it separately. During the booting process I always get Intel536: module license 'Proprietary' taints kernel, but the modem works. I use KPPP under KDE 3.2. When kernel 2.6.10 came, I patched my kernel, compiled it with the same .config file and compiled the 536ep code again, but the modem doesn't work. There's no initialization, no waiting for the OK after ATZ and no dial tone. Of course, the old kernel 2.6.9 still is available and works with my modem. I would appreciate any help, comments or further assistance from you regarding this issue.


Werner Gerstmann


WGerstmann@web.de

You are relying on an out-of-the-main-kernel-tree driver to work properly on future kernel releases. That is almost guaranteed to not work over time, as kernel apis change and morph due to bug-fixes, security issues and feature changes. Please see www.kroah.com/log/linux/stable_api_nonsense.html for details about why the Linux kernel does not have a stable internal kernel api. I recommend contacting the author of the driver and asking him for help, as he is the one that knows the code the best.


Greg Kroah-Hartman


greg@kroah.com

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