Best of Technical Support
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, firstname.lastname@example.org
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, email@example.com
[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, firstname.lastname@example.org
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, email@example.com
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, firstname.lastname@example.org
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, email@example.com
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, firstname.lastname@example.org
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, email@example.com
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, firstname.lastname@example.org
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 filenameor
rpm -q filename-2.0-1In this case, rpm -q filename-2.0-1.i386.rpm will not work, as that is not the package name. —David M. Brown, email@example.com
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.View Now!
|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- The Firebird Project's Firebird Relational Database
- Stunnel Security for Oracle
- My +1 Sword of Productivity
- SUSE LLC's SUSE Manager
- Non-Linux FOSS: Caffeine!
- Managing Linux Using Puppet
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Google's SwiftShader Released
- Parsing an RSS News Feed with a Bash Script
- Doing for User Space What We Did for Kernel Space
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide