  The LINER nucleus of the nearby spiral galaxy M81 was pointed by BeppoSAX,
which caught it at the highest (2-10) keV flux level observed so far. The LECS,
MECS and PDS data, extending over (0.1-100) keV, are used to investigate the
physical similarities and differences between LINERs and AGNs. The continuum is
well fitted by a power law of photon index \sim 1.84, modified by little
absorption due to cold material. Superimposed on the continuum BeppoSAX detects
a 6.7 keV emission line (confirming an ASCA result) and an absorption edge at
8.6 keV. Both spectral features are consistent with being produced by iron at
the same high ionization level, and probably also with the same column density.
So, we suggest that they originate from transmission through highly ionized
thin material. Concerning the origin of the continuum emission, we do not
observe signs of reflection from the optically thick material of an accretion
disk, as usually found in Seyfert 1's (a 6.4 keV emission line and a broad bump
peaking at 10-20 keV). The low bolometric luminosity of the nucleus of M81 is
consistent with being produced by advection dominated accretion; in this case
the X-ray emission should be dominated by Comptonization, rather than by
bremsstrahlung, in order to reproduce the steep spectrum observed over the
(0.1-100) keV band.
