LJ Archive CD

Best of Technical Support


Issue #111, July 2003

Our experts answer your technical questions.

Best of Technical Support

Kickstart from USB Floppy?

I am using the Red Hat Kickstart installation feature for the 7.2 distribution to install a customized version of Linux on several machines. Currently, I use a floppy drive to boot and store the ks.cfg file on the floppy, so the syslinux.cfg file has a line that looks like this:

label ks
kernel vmlinuz
append text ks=floppy initrd.img lang=
devfs=nomount ramdisk_size=7168

How do I start the Kickstart installation using a USB floppy/USB CD-ROM? I can boot using USB floppy/CD-ROM, but the Kickstart installation fails, as it doesn't find the ks.cfg file residing on the USB device.

—Vishali Karnik, Vishali.Karnik@respironics.com

According to their release notes, Red Hat did begin recognizing USB floppy drives during install with the 7.2 release, so this should be possible. I don't have a USB floppy drive to test this, but the helpful people at Fujitsu Siemens Computers have some advice on how to do Kickstart from USB floppies: www.fujitsu-siemens.com/partner/linux/readme/driver-disks-redhat.shtm. USB floppy drives are detected as SCSI devices. If you have no real SCSI devices on the system, you need to change ks=floppy to ks=hd:sda/ks.cfg. If that doesn't work, drop to a shell during a manual install and cat /proc/scsi/scsi to see what device name in /dev is being assigned to the USB floppy. The first device in /proc/scsi/scsi will be sda, the second will be sdb and so on.

—Don Marti, info@linuxjournal.com

Using a Nonstandard Modem

The PCtel 2304 WT modem with my Dell notebook is not detected by Red Hat 8.0.

—Hari Babu Prasad, hari_bsnl@rediffmail.com

In order to use PCtel-based modems under Linux, you must use a driver module. An unofficial home page, linmodems.technion.ac.il/pctel-linux, provides the latest version, a list of supported modems and a pretty good HOWTO.

—Mario Bittencourt, mneto@argo.com.br

I Have No POP and I Must Get My Mail

I just installed an internet server (Red Hat 7.3), and when I try to access the POP3 mail from another computer, it says the connection is refused. I already checked sendmail, and it's running.

—Fausto Garcia, faustog@gesnet.com.mx

There are two halves to a complete mail server configuration, and sendmail provides only one-half: the mail transfer agent (MTA) using the simple mail transfer protocol (SMTP). This is a push mechanism used for delivery of a message to a target system. It does not provide services for clients to pull messages from their mailboxes.

—Chad Robinson, crobinson@rfgonline.com

POP3 is not provided by sendmail in Red Hat; it is provided by a package named IMAP, more specifically, imap-2001a-10. To configure POP3, follow these steps: 1) load the package from rpmfind.net/linux/redhat/7.3/en/os/i386/RedHat/RPMS/imap-2001a-10.i386.rpm; 2) install it with rpm -Uvh imap-2001a-10.i386.rpm; 3) enable the POP3 service by editing the file /etc/xinetd.d/ipop3 and changing the line that says disable = yes to disable = no; 4) start the service with service ipop3 start; 5) make sure POP3 starts every time you boot your server: chkconfig --level 345 ipop3 on; and 6) test your POP3 service. Of course, you need to have a user account in your server.

—Felipe Barousse Boué, fbarousse@piensa.com

USB Keyboard Quits at Boot

I recently upgraded my Compaq Presario 7000 from Red Hat 7.1 to Red Hat 8.0. My USB keyboard worked fine during the whole setup process. Once the unit boots into runlevel 3 or above, however, the USB keyboard no longer works. To get around this, I have edited my modules.conf file so no USB support is ever started, which is not a great solution.

—Doug Poulin, dougp25@yahoo.com

Make sure your kernel includes “USB Human Interface Device (full HID) support” and “HID input layer support”. Try modprobe hid to see if this actually is a module. If so, you might try adding these lines to your /etc/modules.conf:

alias usb uhci
post-install uhci modprobe hid

—Robert Connoy, rconnoy@penguincomputing.com

Linker Error

I am porting my project from Solaris to Linux and am faced with a few linking problems. The linker reports some multiple definition errors on functions. The function is defined in one .C and one .CXX file. On linking the object files created from the compilation of these objects, a multiple definition error is being issued. However, the linking step goes fine on Solaris. Is this a problem with some linker options? I am using the C++ linker on both platforms with the same flags/options.

—Mohit Kumar Singhal, mohitksinghal@rediffmail.com

Compiler/linker options are different between Solaris and Linux, even if you are using GCC on both.

—Usman S. Ansari, uansari@yahoo.com

How to Load a Module at Boot?

I'm attempting to install the Promise SuperTrack SX6000 RAID driver module into Red Hat 7.3 and maybe into Red Hat 8.X some day. After I compile a driver, I know there is more to it than simply running insmod to have the driver module automatically load at boot time. Is there an example or procedure that walks one through what an install shell does? What config files are tweaked and where does the driver go?

—Steven Brown, sdbrown327@charter.net

Driver information goes in the /etc/modules.conf file. For example, the line alias eth0 eepro100 specifies that the eepro100 driver should be loaded for use by Ethernet interface eth0. If the module is for your boot device, you need to use an initial ramdisk. See the mkinitrd man page.

—Robert Connoy, rconnoy@penguincomputing.com

Red Hat has assembled a guide to their boot script layout at www.redhat.com/support/resources/tips/Boot-Process-Tips/Boot-Process-Tips-3.html. You can insert your own commands into this file for execution at boot time.

—Chad Robinson, crobinson@rfgonline.com

This page, www.linux.org/docs/ldp/howto/mini/Modules, gives you some insight on the working of loadable modules. It has the basics. Another interesting page about Linux kernel modules is at www.luv.asn.au/overheads/kernelmodules.

—Felipe Barousse Boué, fbarousse@piensa.com

In Defense of Telnet?

I believe Mr Marti has been tempted into a somewhat facile response to the question regarding telnet [see Best of Technical Support, LJ, April 2003]. OpenSSH is indeed an excellent choice over rlogin and telnet outside a trusted environment. But inside such a network, rlogin, telnet and the other r* commands give excellent and much more convenient service within their respective realms of use. I would not be happy to retire rlogin and telnet especially where I have to deal with older systems other than Linux. As ever with security issues, the cost of protection (embodied, in this case, in the greater complexity and inconvenience of setting up the secure tool) must be weighed against the benefits accrued. Simply replacing rlogin and telnet with SSH is useless unless the network is comprehensively bolted down and firewalled. Again, if appropriate protection is to be obtained, a full analysis must be done.

—Bob Hepple, bhepple@freeshell.org

You have the option of inserting public keys, for user authentication, on the servers to which you connect. Or, you simply can use password authentication. Even if you use password authentication, the password is protected by symmetric encryption with SSH. Today's hardware adds an additional wrinkle to security. Are you sure your broadband router doesn't have a trojan installed to sniff telnet packets and pass them over the network? Are you sure your 802.11 wireless bridge isn't passing your telnet packet over the air? A lot of hardware you have no control over has access to your data. Mr Hepple's assertion that “replacing rlogin and telnet with SSH is useless unless the network is comprehensively bolted down” is wrong. We always speak in terms of “raising the bar” of security and adding “layers of an onion”. You are correct, that if a security solution has high cost, one should perform a threat analysis, but SSH is so easy it is a no-brainer.

—Christopher Wingert, cwingert@qualcomm.com

Modern distributions include OpenSSH by default, and make you go through extra effort to run a telnet server. Thankfully, the convenient choice and the secure choice are the same. SSH with password authentication is as easy as telnet. With properly configured keys, it's easier. Check next month's Linux Journal for some productivity-boosting OpenSSH tips. If you need to log in to your Linux system from another OS, check Rick Moen's list at linuxmafia.com/pub/linux/security/ssh-clients for compatible software.

—Don Marti, info@linuxjournal.com

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