Category: linux

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mdadm RAID5 to RAID6 migration

mdadm makes raid management, even tasks that seem like they could be very complicated very easy. The following demonstrates setting up a (5) disk RAID5 array, and then migrating to a (10) disk RAID6 array.

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RAID50 mdadm

The following is how to setup a RAID50 array in mdadm. I would suggest using a RAID6 array in it’s place, but this is for demonstration purposes.

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Recovery from a multiple disk failure with mdadm

If you lose more disks than you have parity to protect you from data loss, then you’re array is gone. But, quite often you get a temporary failure of several disks at once (bad cable, or failed HBA); afterwards the RAID superblocks are out of sync and you can no longer start your RAID array. Here’s a couple ways to try to get it working again.

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Adding an extra disk to an mdadm array

One of the advantages of software RAID is the flexibility it gives you, that would normally only be available from high end (expensive) RAID cards. This includes the ability to grow an existing array (only for certain RAID levels), which means if you run out of space you can easily plug in a new drive and keep going.

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Monitor Hard Disk Temperature in Ubuntu/Debian

If you already have smartmontools installed, it is fairly straightforward to write a Bash script that finds each disk in your computer, checks it’s temperature, and then shutdown the system if the temperature is at a critical level.

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Send system email with Gmail and sSMTP

sSmtp is a very lightweight SMTP server that is perfect for sending out system emails. In this article, I will show you show to use sSMTP to send email through your Gmail account.

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Shell Script to Watch Disk Space

If you have a big RAID array, that last thing you want to be doing is always checking your available disk space. Let’s setup a quick script to monitor our shares for us daily and to send an alert when it gets over 90% used.

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Monitor progress of dd command

Have you ever had to wait for a “dd” command? Not knowing what’s happening, when it will finish, or how far along it is? It’s actually quite easy to get dd to write it’s progress to the screen. Just follow along to see what I mean.