LINUX NEWS
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Thursday, May 9, 2002TABLE OF CONTENTS
1) Sean’s Notes
2) Linux News
Red Hat 7.3 Released
GPL Upheld in Court
Open Office Releases 1.0
Transgaming WineX 2.0 Review3) Linux Resources
Shell Scripting Tutorial
Watch Out For The Python!
Something for Your CFO
Where's the Support
Making Money With Linux?4) App o’ the Week
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1) Sean’s Notes
One thing I’ve always found unique about Unix has been the filesystem. Unlike other operating systems I’ve worked with, Unix isolates the user from the physical, or even logical layout of the actual disk drives, and mashes it all into One Big File System.
The Unix filesystem is usually comprised of much smaller file systems, each corresponding to a physical entity, such as a local hard drive, or a logical entity, such as a RAID volume, a directory on another computer, or even a file on another filesystem. There’s no reason that one of these smaller filesystems has to have real data, as we’ll see today, the /proc filesystem is completely fabricated by the kernel. There’s also no reason the filesystems have to be the same.
This latter point is probably familiar to you all, in Windows you can have a drive “C:” that is FAT32, a second hard drive “D:” that is NTFS, a CD ROM, and a floppy. The user doesn’t care what the type of filesystem it is, as long as they can access files, and perhaps figure out how much free space is left. Each filesystem has different properties, though; NTFS has extended ACLs, while FAT32 has no permissions at all.
Unix doesn’t use drive letters, and it’s a good thing. Why should a user care that their word processor sits on drive D:? What if that should change? What if you wanted everyone to share that drive, they might all end up with different drive letters? Instead, Unix allows the administrator to attach other filesystems anywhere on the main filesystem, which is called the “root” filesystem. Truth be told, you can mount other filesystems on top of those, but if you do that too much you’ll run into trouble trying to unravel it all.
You can see what you’ve got mounted with the… can you guess?… “mount” command:
mount
/dev/hda2 on / type ext3 (rw) none on /proc type proc (rw) usbdevfs on /proc/bus/usb type usbdevfs (rw) /dev/hda1 on /boot type ext3 (rw) /dev/hde6 on /home type ext3 (rw) /dev/hde5 on /usr type ext3 (rw) /dev/hde7 on /var type ext3 (rw) none on /dev/shm type tmpfs (rw) none on /dev/pts type devpts (rw,gid=5,modeb0) /dev/hde10 on /spool type ext3 (rw)
Line 1 shows that the device “/dev/hda2” (first IDE hard drive, second primary partition) is mounted as the root filesystem (/). “ext3” tells us the filesystem type, and “rw” means that it has been mounted in read-write mode.
You can also see that /boot, /home, /usr, /var, and /spool all reside on different partitions, and even physical disks. So, when I’m in /home/sean (my home directory), I’m using /dev/hde6 (first disk, third IDE channel, second secondary partition). If I go up a couple of directories to the root, I’m back on the second primary partition of the first drive. Thus, the administrator can shuffle around disks without having to reconfigure all the applications, or even tell users.
In the output of the mount command, there were also some non-ext3 filesystems which were mounted on strange devices (none, and usbdevfs). The most interesting of them is /proc, which is of type “proc”, and corresponds to no device. If you cd to /proc, you’ll see a lot of stuff:
ls
1 10271 10813 1580 1745 211 5568 640 devices misc 10182 10272 10814 1581 1747 212 5593 645 dma modules 10189 10273 10882 1606 1760 214 5594 7 driver mounts 10200 10274 10918 1607 1761 215 5595 720 es1371 mtrr …
That “mounts” file looks interesting, being as though we’re talking about filesystems:
cat /proc/mounts
/dev/root / ext2 rw 0 0 /proc /proc proc rw 0 0 usbdevfs /proc/bus/usb usbdevfs rw 0 0 /dev/hda1 /boot ext3 rw 0 0 /dev/hde6 /home ext3 rw 0 0 /dev/hde5 /usr ext3 rw 0 0 /dev/hde7 /var ext3 rw 0 0 none /dev/shm tmpfs rw 0 0 none /dev/pts devpts rw 0 0 /dev/hde10 /spool ext3 rw 0 0
That looks familiar, doesn’t it?
ls -l /proc/mounts
-r–r–r– 1 root root 0 May 8 20:16 /proc/mounts
It’s zero size… (and if you check again in a minute, you’ll notice the timestamp has changed). What’s really happening here is that when we open /proc/mounts for reading, the kernel handles the call. The “mounts” file is tied to a routine that displays the current list of mounted devices. The file doesn’t exist anywhere on disk, it’s just the kernel showing its internals in the form of files.
What about all those directories that are numbered?
ls -l 5314
total 0 -r–r–r– 1 sean sean 0 May 8 20:19 cmdline lrwxrwxrwx 1 sean sean 0 May 8 20:19 cwd -> /home/sean/Documents/Brainbuzz/Linux_newsletter -r——– 1 sean sean 0 May 8 20:19 environ lrwxrwxrwx 1 sean sean 0 May 8 20:19 exe -> /usr/bin/gedit dr-x—— 2 sean sean 0 May 8 20:19 fd -r–r–r– 1 sean sean 0 May 8 20:19 maps -rw——- 1 sean sean 0 May 8 20:19 mem lrwxrwxrwx 1 sean sean 0 May 8 20:19 root -> / -r–r–r– 1 sean sean 0 May 8 20:19 stat -r–r–r– 1 sean sean 0 May 8 20:19 statm -r–r–r– 1 sean sean 0 May 8 20:19 status
Ack! What’s this? It seems to be referring to the gedit process that I’m using to write this! Funny coincidence:
ps -ef | grep 5314
sean 5314 5307 0 May06 ? 00:00:12 gedit /home/sean/Docu…
So, by looking in the numbered directories, we can get information about running processes. If you look at the files themselves, you can gather information such as memory usage, the environment variables in effect, and more.
Remember from above that /proc was mounted read/write. If we can read from the kernel through proc, do you think we can write to the kernel?
echo 1 > /proc/sys/net/ipv4/ip_forward
There, we just enabled the kernel to route packets between interfaces.
echo 0 > /proc/sys/net/ipv4/ip_forward
And we just turned it off.
Knowing what file does what is one of those things you build up over time (plus, it changes from kernel to kernel). If you peek around /proc you can usually figure it out on your own, but I don’t suggest you set random values just to see what it does.
Note that you can’t create files in /proc, only the kernel can do that (many modules create a few files in proc to let you check their status or internal counters).
What was supposed to be a quick primer on the filesystem is going to end up being a series. Now that we know how to check out what’s mounted, and know about virtual filesystems like /proc, it’s high time to put the knowledge to use. Next week, it’ll be mounting and unmounting, and then a closer look at the filesystems that are out there.
Long live the Penguin,
Sean mailto:swalberg@cramsession.com
2) Linux News
Red Hat 7.3 Released
Just in case I’m not the millionth newsletter to mention this, Red Hat released version 7.3 of their flagship product. KDE 3.0 (including KOffice), XFree 4.2, GNOME Meeting, Open Motif, and Kernel 2.4.18 are some of the notables in this release. Also of interest is that Postfix is being shipped along with sendmail. The mirrors are going to be busy for a while, but keep on hammering.
http://www.redhat.com/software/linux/rhl_new_features.html
GPL Upheld in Court
In one of the first decisions of this kind, a US court has upheld the terms of the GPL. The company behind MySQL, and NuSphere were embroiled in a bitter dispute over NuSphere’s reluctance to release some of the code they were selling that was based on MySQL.
http://www.open-mag.com/5943483279.htm
Open Office Releases 1.0
At long last, Open Office 1.0 is released. Open Office is an open version of Star Office. All the functionality you need is in this version, but if you want some of the snazzy fonts, templates, and clip art you’ll have to pony up for Star Office. And yes, Q, it has spell checking. It even prints, too.
http://www.openoffice.org/dev_docs/source/1.0.0/index.html
Transgaming WineX 2.0 Review
Transgaming is pouring work into the WINE project so that it can play popular Windows games under Linux. Their latest release allows some copy protected games to run properly, along with a host of improvements to DirectX support. Here’s a review of this product.
http://www.linuxlookup.com/html/reviews/software/transgamingwinex.h tml
3) Linux Resources
Shell Scripting Tutorial
This a very good introduction to shell scripting. Though it’s not comprehensive, it does touch on most of the things you can do. It’s also pretty heavy on the way you manipulate variables, and as such, is one of the more useful tutorials I’ve seen.
http://www.cs.mu.oz.au/~pde/course/shell_scripts.html
Watch Out For The Python!
Well, you don’t have to fear Python, it’s actually a good language that gives PERL a run for its money. Here is the official tutorial for the language; it starts from the very beginning, so it’s great for the newbie!
http://www.python.org/doc/current/tut/tut.html
Something for Your CFO
Most ROI studies that place Linux against Microsoft simply look at hardware and software costs. Here’s one that takes a look at many other factors, such as operational costs. It’s also based on experience, and not fictitious models.
http://www.linuxjournal.com/article.php?sid=57
Where’s the Support
Network Computing looked at various options for outsourcing Linux support. They got accounts with various places, and placed a series of questions to the support lines, measuring response time, efficiency, and overall quality. The results are surprising, so if you’re looking to outsource some Linux support, you’ll want to read this.
http://www.networkcomputing.com/1309/1309f3.html
Making Money With Linux?
A Cramsession user asks, ”…do you have any ideas on which parts of linux could be a profitable venture for a startup core linux company?” Any advice? What do you see as being a good way to offer Linux-based services to the public, and make a buck off of it?
http://boards.cramsession.com/boards/vbm.asp?mU0426
4) App o’ the Week
As I play with my new burner, I’m amazed at how difficult it is to make an audio CD from MP3s. Here’s a program that does that – and only that. Sometimes the Swiss Army Knife approach to software development doesn’t work, and you just have to resort to individual tools.
http://m1.651.telia.com/~u65105865/make_audio/
(C) 2002 BrainBuzz.com, Inc. All Rights Reserved.
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