Regarding “A Survey of Embedded Linux Packages” (LJ February 2001), thank you, thank you and thank you. I couldn't see the forest because all them damn trees were in the way. Your article really helped shed light on what the names are, who the players are and what the scope of the paradigm is.
Living in Northwestern Pennsylvania, we are kind of out of the Silicon Valley mail loop. I've been on Victor Yodaiken's RTL mailing list for two years and still didn't understand the landscape. Your article really helped.
Thanks for helping us stay current.
—Raymond C. Minich
There is an error in “The Best of Technical Support” in LJ February 2001. “ide-floppy” is not the appropriate module for ATAPI class ZIP drives. ide-floppy works for the original non-ATAPI IDE ZIP drives. The appropriate module is “ide-scsi”. This information may be found in the ZIP drive HOWTO.
This is a very serious difference. From firsthand experience, I know that using ide-floppy on an ATAPI class ZIP drive will seem to work but will invariably cause filesystem damage on the ZIP disk (unless one does read-only operations with it).
One of the examples in Mick Bauer's “101 Uses of SSH, Part II” article (LJ February 2001) gives a misleading impression of security. Listing 6 shows how FTP can be tunneled over ssh port-forwarding. If this were any other protocol (say POP3 or IMAP), things would be fine.
But FTP actually uses two connections, not just one. The primary connection (port 21) is used as a control channel, issuing commands to the server. The secondary channel is set up each time there is data to be transferred on a different and random port, if using passive mode. If you're not using passive mode, the situation gets worse. The server tries to make a connection back to you from port 20. Chances are this will be blocked stone dead by any firewall nearby.
Anyway, the ssh command will only forward the control channel and not the data channel. That is enough to protect your password but not the data that passes between the servers. This is a misleading state of affairs because the connection may well work, even though most of it goes unencrypted!
As far as I know, you cannot use FTP over SSH without implementing special “FTP watcher” routines inside ssh. This is not impossible; practically every NAT device on the market does the equivalent. An alternative might be to use the sftp command from ssh2. However, I'm not sure whether this is included in OpenSSH yet.
You're absolutely correct. While I do think there's some value in encrypting the control channel even if the data channel is not, that was a poor example, especially since I didn't point out that the data channel does in fact go in clear text. But it does work, even without an FTP-watcher: I've been using FTP over SSH in the manner described in my article for a couple of years now. SCP is still the most secure way to transfer files with OpenSSH. SFTP is cool, but only partially supported in OpenSSH (client- or dæmon-only, I can't remember which). But you can use SSH Communications' “official” SSH v.2 for free if you run it on Linux, xBSD, etc., thanks to a new “Free Use for Open Source OSes” clause in its license.
Out of all the articles I've read in LJ over the years, few have had as much impact on me as the one on vim (“That's Vimprovemnt! A BetterVi”, LJ February 2001). I often spend more time in vim than I do sleeping, and thanks to the article, I now have a few more tricks to use. Some of the most glaring features I was not aware of were the third mode (called visual), the command mode grep and split. I learned vanilla vi on Solaris, and there are a lot of features in vim I have obviously not picked up yet. That being the case, have you thought about a monthly feature on editors? Since I imagine a great deal of your readers spend a lot of time in editors such as emacs, vim, pico and the like, perhaps a regular feature is in order.
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.
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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.
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