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JavaScript All the Way Down

LinuxJournal - Thu, 2015, Apr09 - 10:41

There is a well known story about a scientist who gave a talk about the Earth and its place in the solar system. more>>

Designing Foils with XFLR5

LinuxJournal - Wed, 2015, Apr08 - 09:54

For any object moving through a fluid, forces are applied to the object as the fluid moves around it. A fluid can be something like water, or even something like the air around us. When the object is specifically designed to maximize the forces that the fluid can apply, you can designate these designs as airfoils. A more common name that most people would use is a wing. more>>

diff -u: What's New in Kernel Development

LinuxJournal - Tue, 2015, Apr07 - 09:21

Recently there was some discussion about ways to ease the tired backs of kernel maintainers. Apparently the merge windows are times of great labor, and some folks wanted to alert contributors to some preferable code submission habits. more>>

Here, Have Some Money...

LinuxJournal - Mon, 2015, Apr06 - 14:29

I love Bitcoin. It's not a secret; I've written about Bitcoin mining and cryptocurrency in the past. I'm the first to admit, however, that we're at the very beginning of the cryptocurrency age. more>>

Repairing a degraded RAID array

AZ Loco - Sat, 2015, Apr04 - 13:12

First, figure out which hard drive was bad.
To do this, we did this:
look into /proc/mdstat and find out what hard drives are assigned to the raid array. You should be able to identify the drive that is still good. For us the good disk was /dev/sda.
Once we knew it was /dev/sda, run ls -l /dev/disk/by-id. It will show an identification of the disks (usually you could figure out the manufacturer name from there), and linked with it what the drive is referred to /dev/sda, /dev/sdb, etc.). If your drives are from the same manufacturer, you might be able to figure out which one is bad by this command ls -l /dev/disk/by-path. From there, try go figure out what path corresponds to what sata connector. If that still fails, you might need to just pull one of the two disks, and see if your machine boots. If it doesn't, you know that you disconnected the good disk.

Find out the partition size(s) that are raided. We used fdisk /dev/sda, issued the p command to find that out.

Once the bad drive is identified, replace it with a new disk.

Once rebooted, fdisk the new disk.
Create the partition that you want to raid. Make sure its size is the same as you recorded earlier. Make sure that you set its partition type to fe (raid auto detect).

Once formatted, issue the following command as super user
mdadm --add /dev/mdx /dev/sdyz, where you have to replace x and z with the appropriate digits, and y with an appropriate letter.
For example, if the raid array is /dev/md0 and you want to add /dev/sdb1 to the array do this: mdadm --add /dev/md0 /dev/sdb1

You should see the raid array repairing itself by looking at /proc/mdstat

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Consent That Goes Both Ways

LinuxJournal - Thu, 2015, Apr02 - 09:48

Whatever your opinions about Do Not Track, set them aside for a minute and just look at what the words say and who says them. Individuals—the people we call "users" (you know, like with drugs)—are the ones saying it. In grammatical terms, "do not track" is spoken in the first person. more>>

New GeekGuide: Beyond Cron

LinuxJournal - Thu, 2015, Apr02 - 09:45
How to Know When You've Outgrown Cron Scheduling--and What to Do Next

If you've spent any time around UNIX, you've no doubt learned to use and appreciate cron, the ubiquitous job scheduler that comes with almost every version of UNIX that exists. Cron is simple and easy to use, and most important, it just works. more>>

March 2015 Issue of Linux Journal: High-Performance Computing

LinuxJournal - Wed, 2015, Apr01 - 08:43
High Performance: a Relative Term

My Pebble watch has several orders of magnitude more power than the mainframe computers used by NASA to land astronauts on the moon and then get them ba more>>

April 2015 Video Preview

LinuxJournal - Wed, 2015, Apr01 - 08:31

Not So Dynamic Updates

LinuxJournal - Mon, 2015, Mar30 - 09:33

Typically when a network is under my control, I like my servers to have static IPs. Whether the IPs are truly static (hard-coded into network configuration files on the host) or whether I configure a DHCP server to make static assignments, it's far more convenient when you know a server always will have the same IP. more>>

Users, Permissions and Multitenant Sites

LinuxJournal - Thu, 2015, Mar26 - 10:28

In my last article, I started to look at multitenant Web applications. These are applications that run a single time, but that can be retrieved via a variety of hostnames. more>>

New Products

LinuxJournal - Tue, 2015, Mar24 - 11:13
Please send information about releases of Linux-related products to or New Products c/o Linux Journal, PO Box 980985, Houston, TX 77098. Submissions are edited for length and content.

Flexible Access Control with Squid Proxy

LinuxJournal - Mon, 2015, Mar23 - 13:10

Large enterprises and nuclear laboratories aren't the only organizations that need an Internet access policy and a means of enforcing it. My household has an Internet access policy, and the technique I've used to enforce it is applicable to almost any organization. In our case, I'm not too concerned about outside security threats. more>>

Solving ODEs on Linux

LinuxJournal - Thu, 2015, Mar19 - 10:28

Many problems in science and engineering are modeled through ordinary differential equations (ODEs). An ODE is an equation that contains a function of one independent variable and its derivatives. more>>

DevOps: Everything You Need to Know

LinuxJournal - Thu, 2015, Mar19 - 07:13
Have projects in development that need help? Have a great development operation in place that can ALWAYS be better? more>>

Tighten Up SSH

LinuxJournal - Wed, 2015, Mar18 - 15:06

SSH is a Swiss Army knife and Hogwart's magic wand all rolled into one simple command-line tool. As often as we use it, we sometimes forget that even our encrypted friend can be secured more than it is by default. For a full list of options to turn on and off, simply type man sshd_config to read the man page for the configuration file. more>>

Security in Three Ds: Detect, Decide and Deny

LinuxJournal - Mon, 2015, Mar16 - 11:21

Whenever a server is accessible via the Internet, it's a safe bet that hackers will be trying to access it. Just look at the SSH logs for any server you use, and you'll surely find lots of "authentication failure" lines, originating from IPs that have nothing to do with you or your business. more>>


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