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Old 03-12-2020, 01:43 AM   #1
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Question Any way to ADD persist{a,e}nce to *RUNNING* Live USB Ubuntu (19.04)? NO casper-rw present.

I'm RUNNING live and want to SAVE some stuff I've done (install sysdig)
(Meaning: I don't want to reboot!!! btw, I'm not sure how USB was written [by someone else], sorry)

Is it possible? Hints? (or cookbook!)

I spelled it wrong {a} and found:
I then spelled it correctly {e} and found a bunch of obscure stuff...

There are 191 casper files, like /etc/casper.conf /var initramfs-tools ...
(but NO casper-rw)

Here's some output:
ubuntu@ubuntu:~$ sudo updatedb; locate casper-rw
ubuntu@ubuntu:~$ sudo fdisk -l /dev/sdb
Disk /dev/sdb: 14.4 GiB, 15483273216 bytes, 30240768 sectors
Disk model: DataTraveler 2.0
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x46f8e7bf

Device     Boot   Start     End Sectors  Size Id Type
/dev/sdb1  *          0 4095999 4096000    2G  0 Empty
/dev/sdb2       4066772 4074259    7488  3.7M ef EFI (FAT-12/16/32)
ubuntu@ubuntu:~$ df|grep sdb
/dev/sdb         2048000  2048000         0 100% /cdrom
uname-a: Linux ubuntu 5.0.0-13-generic #14-Ubuntu SMP Mon Apr 15 14:59:14 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Netbook: ASUS eeePC 1005PE

P.S. Obviously, there's a LOT I don't know about persistence,
(and [YUMI!!! but not this one] 'live' pendrives),
so I ask patience!!! Thanks In Advance!!! Tutorial links welcome!!!

Found (from 1st 'Similar Threads' at BOTTOM of page) and am reading:

valnar (last Similar): "Loopback/casper files don't allow for full upgradability and would overflow on an apt-get update."
Huh? Isn't that ONLY from making casper-rw partition too small? I've got 10+GB free

Last edited by !!!; 03-12-2020 at 02:07 AM. Reason: ps & pps
Old 03-12-2020, 03:43 AM   #2
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I don't think it is possible. Even if you could add a Casper-rw file/partition you would not be able to use it until you reboot.

In order to modify the USB drive you would need to unmount and that isn't possible unless the system is running entirely from RAM. Currently the system views the drive basically as a cdrom device which is read only and since it is in use, locked.

If the drive is using syslinux to boot the filesystem is vfat which is limited to 4GB files hence the limitation. Casper-rw partitions are a linux ext filesystem and don't have that limitation.

I don't think a running system will actually see the casper-rw file. If using one the it would be a boot option
cat /proc/cmdline

Last edited by michaelk; 03-12-2020 at 04:30 AM.
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Old 03-12-2020, 07:36 AM   #3
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I'm RUNNING live and want to SAVE some stuff I've done (install sysdig)
(Meaning: I don't want to reboot!!!
That would come under the category of poor planning. Reading/research on the subject prior to using and installing software would have been helpful. It won't work the way you want but using another Linux system to shrink the 'live' os partition and then create a casper-rw partition of any size formatted with a Linux filesystem is pretty simple.



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