Best of Technical Support
Our experts answer your technical questions.
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, email@example.com
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, firstname.lastname@example.org[See also man pages for hosts_access(5) and hosts_options(5). —Ed.]
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, email@example.com
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, firstname.lastname@example.org
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, email@example.com
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, firstname.lastname@example.org
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, email@example.com
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, firstname.lastname@example.org
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, email@example.com
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.:
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, firstname.lastname@example.org
More HOWTOs Needed
I have Red Hat installed, but need HOWTO information to use it. How do I get my printer, a “dumb” HP, to work? I downloaded the Ghostscript file to usrs, so what now? How do I get it to open, and in the right place? Is there a manual that is for truly dumb dummies? I have the Linux For Dummies book, but it skips a lot. I do not know how to get into the cc disks except to install. I have been using computers for 10 years, self-taught with books, but these books are short on HOWTOs. —Haroldel, email@example.com
In your installation CD is a User’s Guide rpm which addresses a lot of questions, especially for beginners. For your printer problem (assuming that is already connected to the parallel port):
- Log as root and start X.
- Start Print Tool from the control panel or by directly typing printtool at the xterm prompt.
- Click on Add.
- Specify the printer type (in your case, local) and click on OK.
- Click on Select (next to Filter) and choose the HP model closest to yours.
- Click OK.
- Restart lpd (under Lpd menu entry).
You should now be ready to print; you can test using the Tests item. —Mario Bittencourt, firstname.lastname@example.org
I have a requirement to dual-boot my PC (Linux/WinDoze). I would like to be able to share an e-mail mail box between the two operating systems. Other than Netscape Mail and Pine, is there an e-mail client that runs natively on both platforms and has the ability to share a common mail box? Netscape is good, but the mail filtering rules are limiting. It also handles the summary files differently between Linux and Windows. This results in the Windows summary files being seen as mail boxes in Linux. It is quite frustrating working on one platform only to realize the e-mail you need to read was retreived from the server on the other platform. —Larry Johnson, email@example.com
Rather then answer your questions directly, I propose an entirely different solution. When checking your e-mail, just make sure you “leave mail on server”. Most clients support this. I have set up many a corporate employee who wanted to synchronize their e-mail on a laptop with their e-mail on a desktop computer. —Mark Bishop, firstname.lastname@example.org
I recommend using an IMAP-compatible client to retrieve your e-mail. Pine, Netscape, Outlook Express and many other mail clients support the IMAP protocol. The benefit of using IMAP is that your folders are kept on the server, so your client does not need to store this information locally and attempt to share it with other clients. I do this with Pine under Linux and Outlook Express in Windows and have been quite happy with the results. Just be sure you refresh your folder lists frequently, as most clients will not do this automatically and will miss updates made in other clients. —Chad Robinson, email@example.com
Problem with Boot Disks
I’m a beginner. After creating the boot disk using rawrite with boot.img as its source, I tried to boot using the diskette. After I pressed <ENTER>, my PC froze. Here is the last line of the message:
RAMDISK : Compressed image found at block 0 CRC errorVFS : Cannot open root device 08:22 kernel panic : VFS:Unable to mount rootfs on 08:22
Help. —Rohaimi Razali, firstname.lastname@example.org
Use a pair of brand-new floppy disks, and this problem should go away. The compressed file system placed on the root disk consumes almost all the disk, and any errors on the disk will cause this problem. Usually, replacing the disk with a fresh floppy will solve the problem. The worst-case scenario is a bad floppy drive, but that is unusual. —Chad Robinson, email@example.com
Wiping Out LILO
I cannot remove LILO from my Master Boot Record. Even reformatting the drive completely back to a Windows FAT 16 configuration doesn’t help. A fragment of LILO somehow remains and tries to boot a nonexistent LINUX system, denying me access to Windows, and freezing the system. How can I completely delete LILO from my MBR? —Robert Morgan, firstname.lastname@example.org
There are ways of restoring your original MBR, but since the drive has been formatted, that is not an option. Another method is to first boot from a DOS boot floppy or Win95 rescue diskette. Then run fdisk /mbr which will write a new MBR. —David M. Brown, email@example.com