Best of Technical Support

Our experts answer your technical questions.
Who Goes There?

I have taken over a Linux system for a company. The company uses the box as an Internet server. The problem is that the person I have taken over for left without providing the root password for the box. Is there any way I can find the password, or any way I can recreate it without knowing the original password? —Rusty Mays, rmays@ntr.net

When you get the LILO prompt, press the tab key. Find which kernel name is first (probably “linux”) and type

linux init=/bin/bash

Once you get a prompt, do the following:

mount -wno remount /
/bin/vi /etc/passwd
The old trick was to remove the password field (anything between the 1st and the 2nd colon), but some distributions (notably Red Hat) have a bug (or feature, depending on how you look at it) where it won't let you log in as root if there is no password, and also the password command will not work if the password field is blank. The passwd command should work and let you enter a new password even if you don't know the old one (and leave it in place). If that fails, another option is to replace the encrypted password with a known encrypted one, like yours. —Marc Merlin, marc_bts@valinux.com

The passwords used in UNIX/Linux are usually hard to crack, so the best thing to do is to boot from a Linux boot floppy, then edit the password file. Boot from a set of Linux boot floppies, either for an installation or one of the “Linux on a floppy” installations from http://www.toms.net/rb/. After booting from the floppy, mount the hard disc, then make a copy of the password file, just in case (either /etc/passwd or /etc/shadow), then edit the password file (with vi, pico, etc., or use sed and/or cut) to remove the password for root. Finally, unmount the hard disk and reboot, then log in as root and set the root password immediately. It's probably a good idea to check for other accounts with a UID of 0, and accounts you do not recognize. —Keith Trollope, kt57707@GlaxoWellcome.co.uk

I Can't Get No Resolution

My machine at home has a sis6215 chip, and Red Hat 6.0 doesn't have a driver for it. Probably because of this, when Gnome runs, the screen is zoomed and everything is huge. The default resolution is some 320x200. I tried to configure custom settings through Xconfigurator and also X11Config, but the resolution didn't change. Where am I stuck? Is there some problem with my monitor settings? —Pankaj Ratan Lal, prlal@quantum.ac.in

According to www.xfree86.org/3.3.6/SiS2.html#2, your chip isn't supported by XFree86. You can still try XFree86 3.3.6, but there aren't many chances it will work. If your chip is VESA 2-compliant, you have another option: use the VesaFB frame buffer, available at www.xfree86.org/FAQ/#FBDev. --Marc Merlin, marc_bts@valinux.com

The Dreaded Busy Signal

When I try to set up my modem and use the query modem function, I get a “modem busy” response. This also happens if I use dialup. I use COM3 for my modem, so I set Linux to tty2. I think this is correct. Is it conflicting with Windows? Any suggestions? —Don Hoornaert, richey@mb.sympatico.ca

Even though many things could be happening (misconfigured port settings, broken modem, misconfigured software, etc.), make sure you have all settings correct and try connecting directly to the modem with cu -l /dev/ttyofyourmodem. The “ttyofyourmodem” depends on which COM port you use; it could be ttyS0, ttyS1, ttyS2 or ttyS3 for COM1, COM2, COM3 or COM4, respectively. If you succeed in connecting to the modem this way and get an OK in response to an AT command, then you are okay. If you bought your computer with Windows pre-installed, it is probable that you have what is called a Winmodem, which is a crippled kind of modem for Windows only. If that is the case, you had better buy a modem that works with Linux. I have bought many 3COM USRobotics “Python” internal modem cards that provide 56K V.90 data/fax/voice services to my Linux servers with excellent results. Check this excellent web page for modem compatibilities: www.o2.net/~gromitkc/winmodem.html. Check the entire modem list table. There are some people trying to make Winmodems work with Linux, but to play safe, buy a new Linux-compatible one. —Felipe E. Barousse, fbarousse@piensa.com

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