Best of Technical Support

Our experts answer your technical questions.
TELNET Permissions

How do you disable users from using TELNET to log in to a specific machine (i.e., server)? And is it possible to allow some users to TELNET to a specific machine and some not? —Ethan Bambock,

You can disable TELNET in the /etc/inetd.conf file. Look at the /etc/security/access.conf file to allow access on a per-user basis. —Marc Merlin,

[See also man pages for hosts_access(5) and hosts_options(5). —Ed.]

FTP Stuck

I cannot seem to get the FTP server/service to work. When I attempt to use ftp to access the Red Hat machine from another computer, I get the message “connection is closed by the remote host”. It won't even give me the opportunity to type in a name or anything. I have not had this problem with previous Linux versions. I am on a Gateway Pentium 133 on a 16MB token-ring network. Incidentally, using TELNET works fine. —Steve Mitchell,

There are two possible answers to this problem, depending on the FTP client you are using.

If you are using NcFTP, and you are not forcing it to ask you for a user name and password with -u, it will automatically try to log in as root, if you are logged in as root locally. Most distributions of Linux prevent root logins via FTP for security. You can change this by editing /etc/ftpusers, which is a list of users who may not log in via FTP.

If you are not using NcFTP, the service is either not installed or not correctly configured on the remote server. This is less likely to be the problem, and you can test it by trying to connect from another machine on the local network, as opposed to your home system. In this case, inetd (the service that handles incoming connections and spawns the handler daemons) is either not finding ftpd where it has been told to look or is not able to start the process for some reason. inetd is configured via /etc/inetd.conf, and you may want to look at that file to see if the FTP service is commented out. —Chad Robinson,

Sluggish Server?

For a long time I had no problems with my Linux distribution, but then I switched over to a new system, which had a K6 266MHz and 64MB of SDRAM. For the most part I have no problems, but when running certain applications, namely Emacs, NcFTP and Netscape (I am using Communicator 4.04), I find they load up too slowly and Netscape runs too slowly to use. I've heard this may be because of slow FPU speeds on the AMD but either way I want to know if there is a way to avoid this problem. I would use Lynx for web browsing except that it doesn't support a proxy connection. (My Internet access is through a proxy server.)--Derek Wollenstein,

It sounds to me as if Linux is not seeing all of your memory. You should verify that it is all there with the command free. The total column will indicate how much is recognized. If it does not show (in kilobytes) close to 64MB, you must specifically tell Linux there are 64MB. This is done at boot time, so you must edit /etc/lilo.conf and add the line append = "mem=64M" to the options. Then run lilo from the command prompt and reboot.

One other thing could cause problems. Some BIOS revisions come with an option for “Memory Hole at 15M”, which you should disable. This option is for OS/2, so unless you are running OS/2 you do not need it. —Andy Bradford,

I don't know about the slowdown, but Lynx does support proxies! Look for the file lynx.cfg; it has examples of how to set up a proxy right in the comments. —David M. Brown,

Installing New Packages

Sometimes when I am installing an RPM package, I get messages saying the package is already installed and cannot install; however, when I run the rpm -q to query the package, it says it is not installed. I need certain packages such as Perl that I cannot get installed and do not work. Please help! The frustration is setting in. —Carlo Wise,

Try using rpm -qa | grep perl to list all the packages that might be installed with the name of perl. You can obviously change “perl” to whatever package name you are looking for. —Andy Bradford,

There is some confusion at times as to the distinction between a package name and an RPM file name. There is a difference! When you wish to install an RPM, you use the RPM file name, e.g.:

rpm -ivh

where filename-2.0-1.i386.rpm is the actual RPM file name. When you wish to reference an installed RPM, you must use the package name (with or without the version information), e.g.:

rpm -q filename
rpm -q filename-2.0-1
In this case, rpm -q filename-2.0-1.i386.rpm will not work, as that is not the package name. —David M. Brown,