  Motivated by recent observation of Lanzetta et al. that most luminous
galaxies at low redshifts produce $\lya$ absorption at impact parameter $l\lsim
160 \kpch$, we propose that these absorbers are clouds confined by the pressure
of ambient hot gas in galactic haloes. We determine the properties of this hot
gas and of the absorption systems on the basis of observational and theoretical
constraints. The absorbing clouds need to be replenished on about one orbital
time ($\sim 10^9$ yrs) in the galactic halo. The pressure and temperature of
the gas at radius $r\sim 100\kpc$ are $P=(10-100){\rm cm^{-3} K}$,
$T=10^{(5.5-6.5)}{\rm K}$. The model requires that about 10 per cent of the gas
in low-redshift galactic haloes is in the hot phase. Such gas in galactic
haloes emits x-ray with bolometric luminosity of the order $10^{37-40}{\rm
erg\,s^{-1}}$. The plausibility for such gas to exist in current models of
galaxy formation is discussed.
