I would like to have an Ubuntu USB I can carry around with me at all times just in case I need/want to use Ubuntu on a computer for some reason. (I find it very useful for a lot of things. Gparted and the dd command I often find useful, for example.)

I tried installing Ubuntu to a USB stick directly, However I found that despite it being a USB 3.0 drive it wasn't fast enough to run a full OS from. Performance was very poor.

So, now I am trying to use a persistent USB drive instead. However, I am unclear how the persistence works and as a result what its limitations are.

How far does persistence extend? I presume it will save settings between boots at the least, but will it save files? If I install something with apt-get will that persist? It seems that when I boot on a MacBook the Live USB lacks the drivers required for WiFi, will drivers persist if I install them?


Persistence is saved in a file or partition named casper-rw, a persistent home file or partition named home-rw is also possible. A persistent install will save data, program installs, customized desktops, just about everything except some drivers which are loaded before the persistence file is read during boot, (NVidia graphics).

In a syslinux type install, (SDC, Unetbootin, Universal, Rufus, etc), the system resides in the root of the drive as does the casper-rw file. The filesystem for this partition is FAT32 thus maximum size for the persistence file is 4GB.

Prior to 14.04 syslinux type installs could also use a persistent casper-rw and home-rw partition. Persistent partitions no longer work except with grub2 type installs, (mkusb and the original MultiBootUSB).

Mkusb is easy to use, safe, versatile and will make a persistent partition of whatever size you want, it will then use remaining disk space to make a NTFS partition that is visible to both Linux and Windows.

Limitations, well you don't want to unplug a persistent pendrive while data is being written to persistence, luckily mkusb comes with persistence backup tools.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.