Ubuntu – option like TAIL to keep track of WHOLE file

Use

tail -f -n +1

Using man tail will give you more details, the relevant excerpt follows.

<snip>Numbers having a leading plus (`+') sign are relative to the
beginning of the input, for example, ``-n +2'' starts the display at the
second line of the input.</snip>

-f      The -f option causes tail to not stop when end of file is
        reached, but rather to wait for additional data to be appended to
        the input.  The -f option is ignored if the standard input is a
        pipe, but not if it is a FIFO.

-n number
        The location is number lines.

tail uses inotify which does not work with overlayfs See this bug report and this discussion. @Xen2050 pointed out the ---disable-inotify switch to tail See this workaround

You could use apt-src to install the coreutils source, and recompile tail with -UHAVE_INOTIFY