So I have a bunch of small flash drives around 4 gbs or so. 4 gbs is not enough space for me to store all my files in my persistent liveusb. So is it possible to set up multiple casper-rw partitions across multiple flash drives? So then I could plug in all my flash drives and the live system would detect the individual casper-rw partitions in the multiple flash drives and put them all together to use for space?

I know that you can extend the casper-rw partition but since my flash drive is only 4 gbs, I cannot extend it any further. To clarify, I want to know if you can have multiple casper-rw partitions from multiple flash drives and then if the live system can automatically mount all of them and use them all for persistence. Is this possible, and if so, how can it be done?

Thanks for the help.


There is no limit for casper-rw partition size.

The only limit is for the casper-rw file on a FAT32 partition. FAT32 file size limit is 4GB

A casper-rw partition may be ext2, 3 or 4.

Besides for a casper-rw file on a FAT32 partition you can have a home-rw file, which gives a separate home folder.

Program updates etc will be stored in casper-rw and home folder data will be stores in home-rw

To make a home-rw file rename a blank casper-rw file.

Note that when booting a persistent Ubuntu install, the first casper-rw file or partition encountered is the one used.

I have never found a method of combining casper-rw files but have never had a reason to.

EDIT 2016

At this time, persistent partitions no longer work with syslinux type installs such as SDC or UNetbootin. They do work with a grub2 type install such as mkusb makes.

It is possible to use multiple casper-rw files as long as each is in a uniquely named folder on a FAT32 partition(s). see: MultiBoot with Multiple Persistent partitions

EDIT Aug/2017 - Persistence files > 4GB

Syslinux started adding support for NTFS with version 4.06 but did not offer full support until version 6.03. This allows casper-rw files to be larger than 4GB.

  • So you're saying that it is impossible to have multiple casper-rw partitions? Like for example I have a 4 gb casper-rw partition on 1 flash drive (which takes up the entire flash drive) and another flash drive with the exact same thing, the OS can't use both of them at the same time for persistent storage? I know that casper-rw partitions can be any size, but my flash drives are only 4 gbs and I need more space and do not want to buy a bigger flash drive. – hammy Dec 26 '13 at 20:15
  • Also, if the first casper-rw partition found is the one used, is it possible for me to configure it so after boot it'll automatically mount and use my other flash drives for casper-rw as well? – hammy Dec 26 '13 at 20:18
  • Using multiple casper-rw partitions is beyond my experience, In my seven years of researching the subject of USB boots I have not run into it. Using one stick with casper-rw and another with home-rw should work but I have not tried this on separate sticks. – C.S.Cameron Dec 27 '13 at 3:24
  • If you did get Ubuntu Persistent to use multiple casper-rw partitions how would you control which one to write to? – C.S.Cameron Dec 27 '13 at 3:28
  • I was thinking it could fragment the data across the drives like one part on flash drive 1 and the other part on flash drive 2 or that it would store the data in one flash drive until it got full and then start storing data in the next flash drive. – hammy Dec 27 '13 at 5:29

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