Custom fstab + grub menu in bootable persistent USB created with mkusb

I have created a custom live CD image (erm… live USB, I suppose it’d be more accurate) through a combination of Cubic (to generate a custom .iso) and mkusb to provide it with persistency through a casper-rw partition.

It’s working really well, but mkusb seems to be creating its own fstab and its own grub menu.

One of the things that mkusb does is creating a “regular” NTFS partition so the USB stick can be used as a “regular” storage stick (to save pictures, docs or whatever in it), yet that partition doesn’t seem to be mounted on boot.

It would be great if it could be, because I have a pretty specific use I’d like to give to it (specifically, Docker images which now only seem to work properly if I specify devicemapper as the storage-driver). It would really, really help if I could have that NTFS partition mounted in /var/lib/docker/[storage], but even if I change /etc/fstab while in Cubic, those changes are not reflected in the image that is written to the USB stick.

Something similar happens with the Grub menu. Cubic allows to specify your own, but this seems to be overwritten by mkusb and because of issues with the computers where the stick is going to be used, it would be great if I could add a nolapic flag to the boot line.

Is there any way of doing this?

PS 01: I’m not married to mkusb… I do like how easy it is to get a persistent USB with it and that works on bios with UEFI boot, though but maybe another tool would give me more control?

PS 02: I don’t know much about… anything, really but for this specific use case, let’s say I don’t know much about persistent partitions on bootable USB sticks.

Is there an alternative to mkusb to install Ubuntu on a portable SSD that works with both UEFI and BIOS boot methods?

I’ve successfully used mkusb to install a persistent Ubuntu 18.04.2 LTS system on a new Samsung T5 USB SSD. What is nice about mksusb is that it creates a bootable system that works on a wide variety of computer systems. However, I would like to have a portable ‘real’ Ubuntu installation vs. a live/persistent install that works with both UEFI and BIOS boot methods.

The process outlined here looked like it would do the trick, but in my case I’m just presented with the grub prompt when booting the drive. Note, that I interpreted the step:

Cut grub.cfg from sdx5/boot/grub and paste to sdx3/boot/grub, overwriting the existing grub.cfg file 

…to mean that I should move the new grub.cfg file from /dev/sdx5/boot/grub to /dev/sdx3/boot/grub, overwriting the grub.cfg file created by mkusb and deleting the grub configuration file created by the installation from the installation partition. Also, /dev/sdx3 was not mounted after the Ubuntu installation completed, I had to manually mount it (/dev/sdx5 was already mounted on /target).

Since mkusb without modifications works fine with the T5 SSD drive, I assume that there is something about the Ubuntu 18.04.2 LTS installation grub.cfg file that is causing an issue.

Is there an alternative approach that would work, or is there something inherently different with a portable SSD vs. a USB thumb drive that prevents creating a truly portable drive?

How to Repair Persisent Live USB made using mkusb

I had a working persistent live USB that I made using mkusb and it served me well for several months. It then stopped booting.

I get to the screen where I can select Persistent Live, USB Persistent Live to RAM, etc. I select Persistent Live (selecting Persistent Live to RAM doesn’t help either). It continues but then stays stuck on the screen during the ubunto boot where the dots keep cycling. Upon touching the power button, I see a log of lines that show the following errors along with other lines:

Failed to start Avahi mDNS/DNS [a few more characters follow but I cannot make it out]

Failed to start Login Service

There is a line each for a Failed to Start for (I am recreating the list from shorthand notes so please don’t mind case differences or other slight variations–let me know if you need the exact):

login service VirtualBox Linux kernel module
Accounts Service
Thermal Daemon Service
Network Manager Service
Dependency failed for Network Manager Wait Online

During the boot process, if I select the last option to check and do any fixes (versus selecting Persistent Live Boot), it says nothing was broken and asks me to reboot.

From what I can make out from this help page, I need to create a new live usb and transfer the home directory to it. I am having trouble creating a new one (will create a separate thread) but wanted to see if anyone has encountered a similar issue and fixed it without creating a new persistent live usb.

Thanks for any help!