How would I create a RAMDisk on OS X for a read-only filesystem, so that any attempted writes to the drive (which is read-only) are directed to the RAMDisk instead?
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Is this a read only disk (I.E> a CDROM) or a DMG file (Disk Image?)– JoshOct 12, 2009 at 20:44
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3 Answers
You may want a UnionFS mount...
I'm not sure exactly how you'd do this, most likely you'd create a RAM disk, put a DMG file on that, and then mount the DMG with hdiutil attach -union / file.dmg
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There are quite a few articles that explain how you can create a RAM disk:
- you can create a RAM disk using the Make RAM Disk utility,
- this article over on macosxhints.com gives instructions on how you can create a RAM disk larger than 2.2 GB
The part about the redirection is a bit trickier, I'm not sure how you can do it.
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Thanks, and yeah, creating the ramdisk isn't that hard. The second part is a bit tougher...– indragieOct 6, 2009 at 20:27
This line is a keeper... it may not be exactly what the OP was looking for, but it will surely make someone happy. And there's a lot you can learn for it too.
diskutil erasevolume HFS+ "ramdisk" `hdiutil attach -nomount ram://1165430000`
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3I suggest you explain what it does, in detail, if it may not be exactly what the OP was looking for.– Daniel Beck ♦Nov 4, 2011 at 16:40
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It's an answer to the first part of the OP's question, "How would I create a RAMDisk on OS X ..." It will create and format a HFS+ ramdisk, then mount it as /Volumes/ramdisk. The big number at the end changes the size of the ramdisk. It's in sectors or something I can never remember. Nov 11, 2011 at 14:25
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This article explains more details on the command line way: blog.macsales.com/…– VejJan 19, 2020 at 12:40