Recommendations on cloning a bootable main disk

[Bruce Labitt]

It' apparent that one uses a variant of dd.  What isn't apparent is how 
one goes about cloning one's primary disk (active).  From searching it 
appears it is not recommended to use dd when the disk is active, either 
the source or the destination.

I'm trying to clone my nearly full SSD with the OS (Ubuntu 18.04) to a 
new larger SSD.

Is there a tiny linux I can boot into that I can run dd from?  Or can I 
make the main disk ro?  What do you suggest?

I have backed up home.  I really don't want to re-install the OS, since 
I have had troubles with gdm3 screwing up (different topic).  (Black 
screen, no consoles)

Recommendations/recipes on the cloning process sought.

I was simply going to use

# dd if=/dev/sda of=/dev/sdc bs=4096 conv=sync,noerror

I've seen lots of comments about block size and optimal setting, but I'm 
not sure what is optimal if there are unknown (but few) source drive errors.

Thanks,

Bruce