LJ Archive


rss2email—Excellent Article

Thanks to Kyle Rankin for his “Command-Line Cloud rss2email” article in the October 2013 issue. I've been lamenting my “loss” of RSS feeds for some time, and this is a perfect solution!

Steve Hier

I love that Linux affords us multiple solutions to our tech problems. I've tried a handful of Google Reader alternatives (settling on commafeed), but I love seeing how other people tackle the problem as well. Kyle's penchant for simplicity certainly comes through with his preference for rss2email. I'm pretty sure Kyle would be happy with just a constant stream of 1s and 0s, but he's not quite willing to admit it!—Shawn Powers

LVM, Demystified

Regarding Shawn Powers' article “LVM, Demystified” in the December 2013 issue: I've been a fan of LVM2 from the beginning. (LVM1 really wasn't ready for Prime Time.)

You said in your article “LVM is an incredibly flexible, ridiculously useful and not terribly complicated to use system.” I agree totally. However, it is not without its idiosyncrasies.

If you do a followup article, you may mention a few things.

1) There was a bug where trying to pvmove an entire volume with multiple LVs on it sometimes hung up LVM (at least the progress of the move), necessitating a reboot. The recommendation if you had a level with this bug was to move each LV individually.

This had the side benefit of allowing you to “defragment” the segments of your LV (by moving the segments in order and filling each PV). This makes no difference to performance, but makes it easier to see “what you have where”. Tedious, but it makes the neat freak in me happy.

The Red Hat Advisory was RHBA-2012:0161-1; Bugzilla BZ#706036.

2) The metadata present on each PV now eats up a PE (that is, in your case, “not usable 3.00 MiB”, but it's usually 4MB), and it is a good practice to have metadata on every PV! That means that, for example, if you have 5 * 100GB PVs, you don't have 500GB to use, you have 499.9something GB—that is, 500GB minus 20MB (5 PEs, each 4MB in size). This is a problem mainly with SAN LUNs, as they are usually precisely some size.

This means that if you allocated -L 500G, it would fail, telling you that you were slightly short of what you needed. A subsequent -l 15980 would give you almost 500GB and would work. (I think I have my math right here, but you get the picture.)

3) lvdisplay --maps ... and pvdisplay --maps are your best friends if you want to understand basic LVM.

4) Don't try to pvmove a swap volume. Simply allocate a new one and delete the old one.

Excellent article. It's not an easy concept to get across to the novice, but once you understand it, it seems so simple.

Tom Lovell

It's always tough for me to decide how far to travel down the rabbit hole when approaching a topic like LVM. By sysadmin standards, I'm a noob myself, since I avoided LVM for so long. I figured it was worthwhile to bring folks up to my comprehension level, even if I wasn't a zen master.

I said all that to say that I really, really appreciate letters like yours. Not only do I get to learn more, but it benefits everyone who reads Linux Journal as well. And, now I get to go play with more LVM stuff!—Shawn Powers

Bird Feeder

Shawn Powers' bird-feeder article (see “It's a Bird. It's Another Bird!” in the October 2013 issue) was one of the most appealing I've read in LJ since 1994. It's something I often contemplated, but never got beyond that. Many thanks for pointing the way.

An FYI, I alone have turned about six people into active viewers, so I do hope you have plenty of capacity, if only so I don't get locked out now. It's a very pleasant diversion. And you've put out a great bird buffet. Based on my own feeders, you will be kept quite busy keeping them full as word spreads in bird land. And of course, one really has to keep doing it throughout the winter now, as some birds become dependent on them.

Bob Kline

It was my favorite article to write, up there with the article on the arcade cabinet I built and submitted back when I was a freelancer. I'm starting a followup article now, which will probably be published...hmm...in February? I've been tinkering with BirdCam, adding multiple cameras, motion detection with “motion”, archive video creation—all sorts of cool stuff.

Thank you for the e-mail. I'm really glad you enjoyed the article and the camera. I have it scaled out to my Dreamhost account, so it should be able to handle lots of hits. I zoomed in the camera closer to the feeders (you probably noticed), and embedded the window cam and a closeup of the bird bath. It's so funny to see the starlings in the bird bath. I might point a camera there to capture video!—Shawn Powers

Linux Archive DVD

I would be very tempted by the Archive DVD, if there were PDF or Mobi versions of the back issues available on the Archive. I love the idea of using grep to search the HTML versions, but it would be nice to send an issue (once found) to your favorite reading device.

I know matching the original print format with a digital format is a painstaking process. Maybe you could make it clear it is an approximation or use a new “different” automated format for the back issues?

The digital versions of the back issues would be useful for LJ readers who have become accustomed to carrying our LJ issues on Kindles, tablets or phones.


The Archive DVD used to confuse and frustrate me as well. I thought it was a simple collection of past issues that I'd be able to flip through like a pile of magazines. It's grown on me over the years, however, because I see it as more of a collection of articles unbound from the magazine format. Organization is still by issue, yes, but clicking through is a different experience.

Subscribers have access to back issues in whatever digital format is available (all formats for issues going back to September 2011, and PDFs of all formats from April 2005). We don't, unfortunately, have digital versions going all the way back, but those that exist should be accessible on your subscriber page. Hopefully that helps!—Shawn Powers

iPad App Issues

I've been using my iPad for viewing the digital subscription since the printed version ceased to exist. I think there needs to be a major update to your newsstand app. I've downloaded every issue to my iPad, but I cannot view any of the downloaded issues without an active Internet connection. For some reason, this evening I'm not able to connect to whatever service controls your downloads. Not only can I not download the latest issue, but I cannot view/read any of my existing already-downloaded issues! Reading my previously downloaded issues should not rely on nor require an active connection to anything. When I'm not having a problem connecting to your servers, all my downloaded issues say “Read” next to them; when I am having an issue, they all switch back to “Download”. Please address this issue as soon as possible. Having to give up my print issues was hard enough, but this just compounds the problem.

Thanks for a great magazine!

Jon Simonds

I don't have an iPad personally, but I've noticed with my wife's that the iOS7 implementation of Newsstand, at least as it pertains to the Linux Journal app, is frustrating at best. To be honest, I download either the .epub or .pdf directly and peruse the issue from there. We'll work with our vendor to try to get things working right with Newsstand, but I expect the process to be lengthy and frustrating! The downloadable copies you get links for as a subscriber should load right into the iBooks app if you're having issues with the Newsstand app. Hopefully, things will be straightened out soon. I have found in the past that deleting and then re-installing the Linux Journal app sometimes helps as well.—Shawn Powers

LJ Archive