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Does booting a live USB (with persistence turned off) cause writes to occur to it?

rated 0 times [ 4] [ 0] / answers: 1 / hits: 716 / 1 Year ago, thu, may 25, 2023, 1:35:21

I know that Ubuntu will not and can not write to a live CD-R/DVD+-R when it is booting from it, as it is a read-only medium. However, the procedure (at least on the data level) for running Ubuntu off an optical disc is different from a USB drive, which is usually write-enabled. if I make a live USB, turn off persistent files, and boot from it, will any data be written to the USB drive (e.g. settings, error logs, temporary files)? Or will Ubuntu just read from it, nothing else?

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tatoethin

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answered 1 Year ago anatta · Accepted Answer

A live USB acts just like a live CD. Like a live CD, booting is accomplished by extracting a 4 GB filesystem from a highly compressed 700 MB SquashFS image. SquashFS is read-only, so any data that is "changed" in the live session is written to a ramdisk, which (as it's name implies) is kept in RAM and removed on shutdown.

However, you may choose to actually install Ubuntu to a flash drive if you wish. This will cause Ubuntu to treat it as a hard disk, therefore causing it to write to the drive. Note that because Ubuntu needs to be installed on a write-enabled filesystem, you will not be able to use SquashFS and will need the full 5GB (as opposed to ~700 MB) of space required by an uncompressed Ubuntu install.