Best of Technical Support

Local-Only Domain Name?

When setting up a small home network (Red Hat 9), where your only connection to the Internet is through a dialed-PPP connection, what is the best practice for picking a domain name for the network so it won't clash with some valid domain name when you're connected to the Internet? Is there some kind of standard, internal-only domain name, similar to a hostname of localhost for 127.0.0.1?


Steve Cavender


SyntheSys@csi.com

You do not need any name; your Internet access will be fine without one. If you really want one, then register yourself a domain name.


Usman Ansari


uansari@yahoo.com

RFC 2606 reserves the .test top-level domain for testing; no .test domains will be assigned on the Internet. Or, if you don't want to pay to register a domain, and you have a friend who's into DNS, you could ask for a subdomain of one of his or her domains.


Don Marti


dmarti@ssc.com

Red Hat uses localdomain (your machine defaults to localhost.localdomain).


Marc Merlin


marc_bts@google.com

Act on a Change to a File

When using a cron job, I know a process is executed on a certain schedule. Is there any way to execute a process once there has been a change in a directory or file? If so, how would one do such a thing?


Iman Ahmadi


imanahmadi@hotmail.com

One way is to use Linux Directory Notification. You can find documentation and examples in the Documentation/dnotify.txt file under the kernel source.


Usman Ansari


uansari@yahoo.com

You can have your cron or at job check one of the timestamps of the file or directory. The easiest way do that in a shell script is to use GNU find's "%T@" or "%C@" format specifiers. This returns the modification date (%T) or the ctime (change status) date in seconds since the epoch. You can specify a number of other date formats if you like, but seconds since the epoch is handier for some forms of date arithmetic. A more-advanced approach would be to monitor the file or directory access with FAM (file alteration monitor). See oss.sgi.com/projects/fam/faq.html, but this is beyond a simple shell script.


Jim Dennis


jimd@starshine.org

I Have No init and I Must Boot

My Mandrake system shows the following error when I try starting up Linux:

mount:error 22 mounting ext2 flags
Kernel panic:no init found.
Try passing init=option to kernel

I've successfully booted it three times, but thereafter it has stopped booting and keeps showing this message. What can I do?


Devi


deenadev_20@hotmail.com

A Linux kernel mounts the root filesystem and runs a program named init, usually found in the /sbin directory. You could read the kernel sources to find the other three or four places were Linux looks for a program named init. You also could pass the kernel a command-line or bootloader option init=/bin/sh, or some other full path to a program that the kernel would try to load. That's what the rest of this error message is trying to tell you. The question becomes: Why is your kernel unable to find the init program? The most likely cause is you are trying to mount something other than the root filesystem. If you tried to boot up and you passed the kernel a root=/dev/hda6 ... or some other device/partition path to a valid filesystem that didn't have /sbin/init on it, this is exactly the error message you'd receive. Actually, if it also didn't have a /dev/ directory on it, you'd get another error message: “Warning: Unable to open initial console.” That is not a fatal error, but perhaps you also were getting that error and not noticing.

If you had a completely bogus root= directive, if there wasn't a Linux-supported filesystem there, you'd get a different error, something like: “VFS Kernel panic. Unable to mount root.”

Other possibilities are that you had the system set up correctly but accidently removed or renamed /sbin/init or the /sbin directory, or your filesystem is so corrupt that /sbin/init's directory entry or inode is inaccessible.

In any event, I'd boot from a rescue disk, possibly a BBC (bootable business card), such as one you might download from www.lnx-bbc.org. Burn to a CD-ROM; a mini-CD or business card format usually are used for these, but a full-sized disk will work too. Boot from the BBC or Tom's Root/Boot (www.toms.net/rb), and run fsck on each of your filesystems. Then, look them over and figure out which one is really your rootfs. Next, try booting manually, passing the paramaters root= and init= using your bootloader (GRUB or LILO). Then try fixing the /boot/grub/menu.lst (grub.conf) or /etc/lilo.conf to list the correct kernel parameters properly (if that turns out to be the cause of the whole problem). While you have the system booted up from your BBC or other rescue media, it would be a good time to ask yourself: Is there any data I haven't backed up on these filesystems? Is now a good time to copy that data off to some other media? In the worst case you can re-install. There's no shame in saying: “My data is backed up; I don't understand all this fscking and those bootloader config files. Heck with it!” and then doing a re-install.


Jim Dennis


jimd@starshine.org

Minicom Is Not pppd

I am having trouble getting on-line. I am using Minicom and have set up PPP (using Red Hat 6.1). When I dial with Minicom, it appears that I connect, but then it asks for a login and password. I enter my user login and a bunch of charactors pop up, but then after a minute, it says “No carrier”. Any idea of what I am doing wrong?


Chris


calf@lanset.com

You aren't doing anything wrong; you're simply not using the right program for the task. Minicom is a terminal program; it cannot establish a PPP session and allow you to be a client of the remote network. You need a program like pppd, which should be part of your distribution. However, because your distribution is relatively outdated, you may have problems connecting to your ISP, depending on the version of pppd included. If so, you should install a newer version of pppd or upgrade to a newer distribution, depending on your skill and comfort level.


Chad Robinson


crobinson@rfgonline.com

Try the graphical kpppd or something similar. You also may want to update your distribution. Currenly Red Hat 9.0 is out, and you will be pleasantly surprised by it.


Usman Ansari


uansari@yahoo.com

Connecting to a Company VPN

The company for which I work has a VPN that uses Microsoft's VPN server. Is it possible to connect to this using Linux (Red Hat 9)?


Dean Siewert


dsiewert@execpc.com

There is a Linux point-to-point tunneling protocol (PPTP) client compatible with Microsoft's VPN servers. Visit pptpclient.sourceforge.net.


Chad Robinson


crobinson@rfgonline.com

Be sure to find out which protocol they are using. The standard way of creating a VPN with Microsoft products was the built-in PPTP. Recently, they have adopted IPSec and L2TP.


Mario Bittencourt


mneto@argo.com.br

A PPTP server for Linux is the PoPToP package, www.poptop.org.


Jim Dennis


jimd@starshine.org

Re: August 2003, Best of Tech, “Dual-Boot System Skips LILO Menu”

Both answers as printed will work, but both assume the existence or availability of a rescue floppy. If there isn't one, a fix can be made with the first Red Hat install CD: 1) Boot from Red Hat 9 CD #1. 2) Type the boot option linux rescue. 3) Choose whatever language and keyboard options are relevant. 4) At the Rescue prompt, choose Skip. 5) At the shell prompt, type cd /mnt. 6) Type mkdir sysimage. This folder could be named anything. However, Red Hat included a folder by this name for this reason back in Red Hat 7.3, so I'm including it here for mnemonic purposes. 7) Type mount /dev/WHATEVER sysimage/. Mount your / partition here. 8) Type chroot sysimage. 9) Mount /usr and /boot partitions, if necessary. 10) Type grub or /sbin/grub. 11) Type root (hd0,0). This tells GRUB where to find its second-stage loader and config files—in this example, the first partition of the first hard disk. 12) Type setup (hd0). GRUB is placed in the MBR of the first HS. 13) Type quit. 14) Type exit until you are logged out of all shells and Red Hat reboots. info grub has a lot of good info that would flesh out this bare-bones tutorial.


Daniel Callahan


proteus@eclectic-cheval.net

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