Best of Technical Support

Our experts answer your technical questions.
Adding New Users

I am having extreme difficulty adding users on Red Hat 5.1. I've used various methods to add them to my system via the adduser command and through various X control-panel programs. When I add them, everything seems to go well, and they exist when I look them up after I created them. My problem is that I can't log in without being root. If I attempt to log in as a user, it will say “login incorrect”, as if I typed in the wrong password or user name, which is not the case. I have tried numerous times and am frustrated since I cannot get any users to work on my system. —Anthony Dipaula,

You will need to check two files. The first is /etc/passwd. Make sure each user has a valid shell and home directory. Then look at /etc/login.conf. This defines login control settings, and you might have a setting that prevents non-root logins on the console. —Chad Robinson,

File Type

Can someone tell me what the hyphen after a file name indicates? Two examples are in /etc: passwd- and group-. Thanks in advance for the answer. —George R. Boyko,

These are backups made by the utilities that manage these files. You can most likely delete them safely, but it's also a good idea to keep them around. Otherwise, if your passwd file ever becomes corrupted, you will be unable to log in, and rebuilding it is always a pain if you don't have a good copy lying around. —Chad Robinson,

Voice/Faxmodem Problem

I have a multi-platform computer running Windows 95, Windows NT 4.0 and SuSE Linux (kernel 2.0.36). My problem is that I don't know how to install the Plug and Play modem on Linux. With the first two operating systems (Windows 95 and NT), the modem works just fine. I tried many ways of installing the modem using the Isa PNP tools. It recognizes the modem, but I still have trouble setting up the port. I read some of the HOWTOs and they don't help me much. They say to set up the modem with the setserial command, but I don't know how to use this command. In the Windows NT 4.0 setup, my modem is installed with the following parameters: COM5, IRQ 07, Input/Output Range 02E8 to 02EF.

Can someone tell me how to set up my modem on Linux? Or how to set up the modem using the setserial command? It is a 3Com US Robotics 56K Voice Faxmodem. —Manuel Enrique,

COM5 is usually (not always) a clue that your modem isn't a modem but a winmodem, which would therefore be useless with anything other than Windows.

Now, if it really is a modem, you should find out which port it is on as far as Linux is concerned (probably ttyS2) with dmesg | grep ttyS right after boot. Then configure the interrupt and the port number like this:

setserial /dev/ttyS2 port 0x3E8 irq 2

substituting the right values for your card. —Marc Merlin,

Java Crashing Netscape?

I am somewhat more than a newbie, but when it comes to things I don't know, I am clueless. I am running on Red Hat 6.0, and Netscape Communicator 4.5. Whenever I go to a Java web site, like or, Netscape will crash; that is, it will just disappear. If I run Netscape in a terminal ./netscape, it will also disappear whenever I go to a Java site. But in the terminal, it will say “bus error”. What does this mean? I know I enabled Java in my setting, but how can I fix this? —Eric Zabinski,

Netscape has been known to crash for a variety of reasons, many of them linked to Javascript and especially Java. I recommend you try upgrading to Netscape 4.61, or downgrading to Netscape 4.08. —Marc Merlin,

PPP and Network Configuration

I recently accomplished my first successful Linux install, Red Hat 5.2. I installed PPP software, but thought network configuration should be done only for NIC-equipped machines, not ones just doing dialup, so I didn't perform the network configuration at that time.

Although I have subsequently edited a raft of PPP-related files using the HOWTOs, books and the suggestions of an ISP, I don't get the expected PPP “garbage” (40-character frames with frequent { characters) in response to a pppd command from the command-line prompt. Does this clearly mean that I don't have PPP support properly installed and need to reinstall or add via a package manager? Or would this also occur with errors in the configuration files (like host.deny or host.allow or ...)? —Stephen S. Rinsler,

You should be able to create the PPP connection with netcfg, which you can launch from the control panel that should be there by default when you log in as root and launch X (type control-panel otherwise). You also have the option of using linuxconf to create your PPP connection. —Marc Merlin,