  We present a new time-series VI CCD photometry of the globular cluster NGC
6397, from which we obtained and analysed the light curves of 35 variables
carefully identified in the cluster field. We assessed the membership of the
variables with an astrometric analysis based on \emph{Gaia} DR2 data. The
cluster colour-magnitude diagram was differentially dereddened and cleaned of
non members, which allowed us to fit isochrones for [Fe/H]$ = -2.0$ dex in the
range 13.0--13.5 Gyr, for a mean reddening $E(B-V)=0.19$, and a distance of 2.5
kpc. This distance was confirmed using the period-luminosity relation for the
cluster's five SX Phoenicis variables (V10, V11, V15, V21, and V23) present
among its blue stragglers, yielding $2.24\pm0.13$ kpc. We also modelled the
light curves of four eclipsing binaries (V4, V5, V7, and V8), and gave the
parameters of the systems; the contact binaries V7 and V8 have distances
consistent with that of the cluster. NGC 6397 appears to harbour no RR Lyrae
stars, being its horizontal branch remarkably blue, much like that of its
analogous cluster, M10. To match the blue tail of the horizontal branch
population, models of 0.64--0.66 $M_\odot$ with mass loss at the RGB are
required, indicating rather thin shell masses for the HB stars.
