First the question:Is there a file size limitation or any other reason why a livecd.sqfs file, larger than ~4GB, fails to mount when PCLOS is being booted as a LiveUSB?
The ISO container has a file size limitation of ~4GB for any file it contains. This thread is not concerned with that limitation, as far as I am aware.mksquashfs
command is capable, it seems, of producing a file up to a very large size (2^64). Of course the file cannot be included in an ISO if it exceeds the file size limit of ISO.
But, it can be used on a USB device of suitable size, in the same manner as described for manually creating a LiveUSB device.
The PCLinuxOS-liveUSB creator uses similar method to extract files present in an ISO and arranges the device as in the manual method.
So, there being no immediate limitation on livecd.sqfs file size, or on the media it is used on, I created several livecd.sqfs files of 5.6GB and 11.2GB each in size, and attempted to boot the system as a liveUSB device.
The OS boots, seeks and finds the .sqfs file .......... but then fails to mount it.
Following is the Debug output as best I can recall it ...... my comments in Blue
DBG: Devices to check .... <======== Lists all partitions on the PC
DBG: I am after bootfrom. The loopmount is:
Searching for the loop image
/dev/sr0 <======== No media present so no action
/dev/sr1 <======== No media present so no action
/dev/sr2 <======== No media present so no action
/dev/sda1 <======== Finds first searchable media for loop image
DBG: mounted /dev/sda1 <======== Mounts media and searches for loop image
/dev/sda2 <======== Fails to find loop image on /dev/sda1 so moves to /dev/sda2
DBG: mounted /dev/sda2 <======== Mounts /dev/sda2 to search for loop image
[OK] <======== Found loop image
Mounting loop image on /initrd/loopfs:
mount: mounting /dev/loop0 on initrd/loopfs
Failed: Invalid argument
Error: Unable to mount loop filesystem
losetup /dev/loop0 initrd/cdrom/livecd.sqfs
mount -r -t squashfs /dev/loop0 initrd/loopfs
Most likely cause is bad burn or bad download ..... <======= etc
Dropping you to a limited shell
The livecd.sqfs files were created by mylivecd. I choose to not have it delete the files and so was able to use them.
It failed of course to produce an ISO because of the file size limit of the ISO.
Nonetheless the isolinux
directory and the livecd.sqfs
file were available for use on the USB flash stick ...... a 16GB stick I often use for testing such as this.
To check if the .sqfs file was good, I loopmounted it in my installed PCLOS without any problems.
I even used the same commands used when booting to see if there was anything I could find there.
No problems mounting and accessing the content.
I think that about covers the relevant info, and leads back to the question ....what might be causing the failure to mount the livecd.sqfs file?
Presently I am wondering if there is something else with a file size limit that I do not know about .....
Note: I may update this first post as required.