Linux Pro Magazine
"Linux Magazine delivers insightful technical articles on a range of topics related to IT technology."
Monthly (12 issues/yr), with DVD, usually with a Linux distro.
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$99.95/yr (averages to $8.33/ issue, vs. $12.99 per single or back issue)
http://shop.linuxnewmedia.com/us/magazines/linux-magazine-linux-pro-magazine.html
Try it first with 3 trial issues for $3 total:
http://shop.linuxnewmedia.com/us/magazines/linux-magazine-linux-pro-magazine/trial-subscription.html
Admin Magazine
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$59.95/yr (averages to $9.99/ issue, vs. $15.99 per single or back issue)
http://shop.linuxnewmedia.com/us/magazines/admin-magazine.html
Linux Journal
ChemIT has not subscribed so we can't confirm quality or relevance.
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(In addition, subscribers have access to their PDF back issue library.)
https://www.pubservice.com/Subnew1.aspx?PC=LJ
$29.50 for 12 digital issues (averages to $2.46/ issue, vs. $5.99 for single, back issues)