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Kernel arguments are passed in the kernel line of the bootloader--usually GRUB.
Here one example:
kernel /boot/vmlinuz root=/dev/sda4 ro
This is decoded as follows:
/boot/vmlinuz ##path to the kernel, beginning from root, as defined in the previous statement (in this case, the 4th partition on disk 1.---in "grub-speak", starting from 0)
root=/dev/sda4 ##tells the kernel where to mount the root (/) of the filesystem
ro ##tells the kernel to initially mount the filesystem read-only
There are various web sites with listing of all the possible arguments.