Use .rev files from the command line

Sometimes, when you download a big multi-part rar file, a part gets corrupted, or it is not even available. Often, however, .rev files are made available, and they’ll let you extract the file even with missing/corrupted parts. In fact, they let you re-create these parts, in a way similar to RAID-5/6 for hard disks.

Rar files

You can use the command line rar tool to do all the job. First, head over to rarlab, the official site, and download the appropriate version for your OS.

On Linux and OS X, you might want to move the binaries into your path, for example into /usr/bin.

Then, cd into the directory where your parts reside (together with .rev files, you need one for each damaged part you wish to recover), and launch:

rar rc yourfile-part01.rar

The rc switch tells rar to ReConstruct any missing parts (I’d advise you to move somewhere else or delete any damaged parts). Point it to part number 1, it’ll figure out the rest. The process can be quite long, more so for big archives, but it’s worth waiting. After it’s done, you can extract your files as usual, or directly using the command line:

rar x yourfile-part01.rar

Get pretty date differences in PHP

Today I needed a quick way to get the time difference from an UNIX timestamp to the current date. To get an idea, it’s like the little date you see on Twitter.com, for example “5m” if the tweet was posted 5 minutes ago.

Calendar_0

Here’s my quick-and-dirty PHP code, it just takes the timestamp as an input and returns the formatted output. Feel free to fork it and improve it!

Improve software RAID speeds on Linux

About a week ago I rebuilt my Debian-based home server, finally replacing an old Pentium 4 PC with a more modern system (which has onboard SATA ports and gigabit ethernet, what an improvement!). It’s based on an Asrock B75 Pro-3M motherboard, an Ivy Bridge Pentium G2020 processor and 4 gigs of RAM.

Storage Server

I migrated all the drives I had in the old server, including the boot drive, so I didn’t have to configure much. The server has a 200 gb IDE boot drive (connected via a 5€ IDE-SATA converter I got off eBay) and 3×2 Tb WD20EARS 2 Tb “Green” drives configured in RAID-5.

Read speed was finally able to almost saturate my gigabit ethernet, but write speed was still disappointingly slow: about 35-40 megabytes/s via AFP and around 65 mb/s directly on the server.

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