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The context here is the Oneric development ISO. I don't want to have to re-download this every time something changes. I notice that there's a .zsync file in the download directory. From what I know, this should let me update only the chunks that have changed, saving a ton of bandwidth.

The only problem is, I don't have a clue what I'm doing :) Could somebody push me in the right direction to keep oneiric-desktop-amd64.iso up to date?

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Related (but not a duplicate): How to identify and replace broken files in a corrupted Ubuntu ISO? – Eliah Kagan Mar 27 '14 at 6:48
up vote 17 down vote accepted

Turns out I was being dense. A correct Googling and I found my answer on the Ubuntu Wiki. All I need to run is:


I should point out that my previously-downloaded ISO is in the same path as this.

It downloaded the zsync file, checked it against my ISO and updated it to the latest version, 162MB spent. Bargain.

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Testing daily builds with bandwidth caps, I started trying to figure out how to go about this. Oli's posted technique led a response of "No relevent local data found - I will be downloading the whole file."

This is what I had to do to tell zsync to look for the right iso to build off of.

zsync -i /path/to/old/trusty-desktop-amd64.iso

I hope this helps someone else.

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zsync replaces your old ISO with the new one. (It does back up the old ISO... but when you run it again, the newer backup replaces the old.) So by default it assumes the old file is located where you're telling it to download. You can use the -i flag to specify the old file (you can even use it more than once and source from multiple files) or, assuming you want to replace the old file, you can simply make sure you're in the directory that contains it (cd /path/to/old/trusty-desktop-amd64.iso) or move it to the current directory where you wish to download. – Eliah Kagan Mar 27 '14 at 6:57

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