With Ubuntu 19.10, Startup Disk Creator automatically creates a casper-rw partition.

This can be a good thing when using large flash drives so the whole drive is not used for an install that only requires 2.5GB.

So far SDC does not add the word "persistent" to the boot process and thus is not automatically Persistent.

How to use this partition for a persistent install?

Also a 64GB flash drive would allow over 60GB of persistence which seems a bit much.

Is it possible to convert some of this space to a NTFS data partition?

1 Answer 1


How to use this partition for a persistent install?

Also a 64GB flash drive would allow over 60GB of persistence which seems a bit much.

Is it possible to convert some of this space to a NTFS data partition?

  • You can do it in a procedure in several steps, if you have/make only one Ubuntu system (the persistent live USB pendrive) with the cloning method. But it will be complicated, and not recommended for beginners, because you cannot use the most user friendly tool, gparted.
  • Otherwise, if you have another Ubuntu system, you can do it when you make an extracted system according to the previous link. In this case it can be convenient to use gparted to edit partitions and to create file systems,

    • a casper-rw partition with ext2 or ext4 for persistence
    • a home-rw partition with ext2 or ext4 for persistence of the home directory (optional)
    • a usbdata partition with NTFS for exchange of data with Windows

  • This is home territory for mkusb. This tool lets you split the available drive space between a casper-rw partition and a usbdata partition automatically.

If you are happy with converting all of this space to an NTFS data partition, you can do it manually also with a cloned system and test it with the following steps,

  1. Make a live-only drive with any cloning tool, for example the Ubuntu Startup Disk Creator or Win32 Disk Imager.

  2. Boot into it without any [manually added] boot option and let it create a casper-rw partition automatically.

  3. Reboot into it, this time with the boot option nopersistent and reformat the casper-rw partition to a usbdata partition with NTFS.

  4. Checking: Reboot into it again without any [manually added] boot option , this time to mount the usbdata partition and write a small 'Hello World' file.

    echo 'Hello World' > hello.txt
  5. Checking: Boot into Windows, plug in the USB drive and read the small 'Hello World' file.

Please notice that without any casper-rw (and maybe home-rw) partition modifications of the Ubuntu system will not persist shutdown and reboot. In that context it is a live-only drive, where you can use the drive space behind the system to store data and exchange data with other systems, also Windows systems.

Step #3 and the command to create the NTFS file system is crucial:

xubuntu@xubuntu:~$ sudo mkfs.ntfs -f -L usbdata /dev/sdb3
Cluster size has been automatically set to 4096 bytes.
Creating NTFS volume structures.
mkntfs completed successfully. Have a nice day.

xubuntu@xubuntu:~$ sudo partprobe
Warning: The driver descriptor says the physical block size is 2048 bytes, but Linux says it is 512 bytes.

xubuntu@xubuntu:~$ sudo lsblk -fm
loop0  squashfs                                                  0   100% /rofs        1.4G root  disk  brw-rw----
sda                                                                                  119.2G root  disk  brw-rw----
├─sda1 ntfs     System              3AA4725CA4721B19                                   500M root  disk  brw-rw----
├─sda2 ntfs     Windows             786274A362746830                                 117.8G root  disk  brw-rw----
└─sda3 ntfs     Recovery            AAD474DDD474ACE7                                  1000M root  disk  brw-rw----
sdb    iso9660  Xubuntu 19.10 amd64 2019-10-17-12-50-28-00                            14.9G root  disk  brw-rw----
├─sdb1 iso9660  Xubuntu 19.10 amd64 2019-10-17-12-50-28-00       0   100% /cdrom       1.5G root  disk  brw-rw----
├─sdb2 vfat     Xubuntu 19.10 amd64 866D-0A62                                          3.9M root  disk  brw-rw----
└─sdb3 ntfs     usbdata             69F25A82472A1E2C                                  13.4G root  disk  brw-rw----

xubuntu@xubuntu:~$ cat /proc/cmdline 
BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/xubuntu.seed quiet splash nopersistent ---

xubuntu@xubuntu:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 19.10
Release:    19.10
Codename:   eoan
  • 1
    I finally gave up trying to format partition three using "Disks". I used your recommended "sudo mkfs.ntfs -f -L usbdata /dev/sdx3" and it worked beautifully when changing that partition from casper-rw to NTFS. Windows 10 can even see the partition. No need for Windows users to be walking around with a flash drive full of unusable ISO9660, Thank you. Nov 13, 2019 at 5:23
  • 1
    @C.S.Cameron, Now we are aware of solutions, that that we did not figure out before you asked for them :-)
    – sudodus
    Nov 13, 2019 at 8:09

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