Did you try the options in:
File Manager PCManFM > Edit > Preferences > Volume Management > Auto-mount
Unlike all previous versions, 7.6 doesn't automatically mount CDs. I have to type "mount /media/sr0".
Did you try the options in:
File Manager PCManFM > Edit > Preferences > Volume Management > Auto-mount
That doesn't help.
Ok, found the problem. You have to add kernel option:
block.events_dfl_poll_msecs=1000
Looks like a strange command to me but if it works ...
Looks to me like more Linux gibberish. Sure, Linux experts enjoy saying to noobs "you just have to add a kernel option". It certainly demonstrates their superiority and better understanding. But many average users have no idea exactly how you "add a kernel option". It isn't hard to understand why Linux is still marginalized on the desktop.
---
Verifying of md5 checksum and burning a CD at slow speed are important.
At least it's an easy fix, just add it to syslinux.cfg (assuming your knoppix is on a USB stick).
My Knoppix 7.7.0 is a LiveUSB on a Dell Inspiron which has a r/w cd/dvd drive in it.
This implies legacy boot and a remote possibility of systemd messing with things.
I was surprised that cds were not always being recognized, along with other media.
However, I finally noted that, for my set-up anyway, a cd physically in place
in the cd drive reader during boot will be recognized, whereas a cd added after boot
will not be recognized.
So, one work-around for Knoppix 7.7.0 LiveUSB legacy boot users is simply just to
re-boot with the cd in place. I would not be surprised that this problem and work-
around might apply to earlier Knoppix LiveUSBs as well, but I haven't checked this out.

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