Almost Internet with SLiRP and PPP
It's the '90s. More and more people around the world have heard of “getting connected to the Internet.” Some of those have actually made the technological, intellectual, and cultural leap into “Cyberspace”. And some of those are using Linux to get connected. I'm part of all three groups. In fact, I've become rather dependent on my Internet connection—it's like having a telephone, only more expensive.
To be connected to the Internet, you used to have only two choices: either a direct (and expensive) Internet connection, like those used by corporations and institutions, or a modem connection into somebody else's machine which had a direct Internet connection, using your computer as if it were a “dumb terminal”. You can still do that today, if you feel like it, but with the increasingly common availability of “real” net connections like SLIP (Serial Line Internet Protocol) and PPP (Point-to-Point Protocol), fewer Internet users really want to feel as if all they have on their desk is a dumb terminal. Yet, for a number of reasons, the only Internet access available to some of us is a dial-up dumb-terminal-ish Internet account, or “shell” account.
Enter SLiRP. SLiRP is a freely available software package, written by Danny Gasparovski (firstname.lastname@example.org), which makes an ordinary shell account act like a SLIP or PPP account. There are other so-called “SLIP emulators” available (one of the more notable of which is The Internet Adaptor—see References sidebar, as well as “terminal multiplexers” such as term, which uses a non-standard protocol between the shell account and the local computer. SLiRP has advantages over both groups, many of which, along with some disadvantages, the author details in the README file accompanying the SLiRP package.
SLiRP does not run on your “local” computer (the one that would otherwise be a dumb terminal), but rather on the “remote” computer (the one that's actually connected to the Internet). In order to install SLiRP properly, you need the following:
A Unix shell account on the remote host
A C compiler available on the remote host
An editor that you know how to use on the remote host
If you're not sure whether you have a compiler or editor available, please contact your system administrator, or someone else who is familiar with your remote site.
The steps involved in installing SLiRP are as follows:
The most recent version of SLiRP available at the time of this writing is slirp-0.95h.tar.gz. See References sidebar to find SLiRP. Once you have the package, “untar” it somewhere useful (such as /usr/local/src)--perhaps with the command tar zxvf slirp-0.95h.tar.gz.
Documentation of many sorts is included in the SLiRP package in slirp-0.95h/docs. Instructions for compiling SLiRP are in slirp-0.95h/docs/README.compiling, the gist of which is: change to the slirp-0.95h/src directory and run the configure program located there (usually by typing ./configure); then build the program by typing make. If you have problems, consult the file slirp-0.95h/docs/README.getting-help.
When you have successfully compiled SLiRP, you will need to put the SLiRP binary somewhere where you can run it. If you don't already have a directory for your own programs, I suggest creating a directory called ~/bin, and then adding it to your PATH in your login scripts. If you're not sure how to do this on your system, check with your system administrator. Then, from the slirp-0.95h/src directory, perform the following commands:
strip slirp cp slirp ~/bin chmod 0700 ~/bin/slirp
(Alternatively, if your site has GNU `install' available, you may perform the above actions in one step with install -s -m 0700 slirp ~/bin.)
This is the tricky bit, partly because SLiRP is an evolving product, and its documentation is not necessarily entirely complete and up-to-date; however, I suggest reading slirp-0.95h/docs/CONFIG and slirp-0.95h/docs/README.ppp before doing anything else. Next, using your favorite text editor, create SLiRP's configuration file, called ~/.slirprc. At the very minimum, you will want to include a baudrate setting. If you're planning on using SLiRP to emulate PPP, you should also include a ppp flag, an asyncmap setting and mtu and mru values. Your .slirprc file might look something like mine:
baudrate 115200 ppp asyncmap 0 mtu 552 mru 552 log start
You will most likely want to adjust the “baudrate” to suit your modem—some experimentation may be necessary. [“baudrate” should really be bits per second, or bpsrate. Even geeks who happen to know that their 14400 bps modems run at 2400 baud shouldn't set the baudrate parameter to 2400.. —ED]
Once you have SLiRP installed and configured, you can start it by simply typing slirp; SLiRP will then attempt to initiate a connection.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
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.Register Now!
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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