It's process of making Linux even more secure. There are many ways to do that - from tweaking network policies to installing and configuring kernel security modules.
For a desktop PC or a small home server, you don't need to worry about that since Linux is already secure enough by default.
Hardening. Locked-down version of Linux = Hardened Linux Lock-down version of Tomcat: Tomcat hardening
mostly is the hardening done by induction hardening machine, I know also manufactures that do this using the flame hardening method.
in my opinion surface hardening is applied only on the surface while the true hardening is applied in the whole part of the metal....
what the was on tooth hardening day?
Arteriosclerosis is hardening of the arteries.
Depends on your distribution - most well-documented distributions will tell you how to install a hardened kernel along with kernel extensions that help with enforcing security policies (e.g. SELinux).
Case hardening, also referred to as surface hardening is the process of hardening a surface of a metal. It is done by surfacing the metal surface with a layer of metal on top of it, in order to harden it.
-sclerosis means hardening, such as arteriosclerosis (hardening of an artery) or nephrosclerosis (hardening of the kidney).
Sclero means a hardening from the greek word "skleros". Sclerosis means a hardening of the skin.
Case hardening or surface hardening is the process of hardening the surface of a metal, often a low carbon steel, by infusing elements into the material's surface, forming a thin layer of a harder alloy.
Glomerulosclerosis means hardening of the glomerulus.
Core hardening refers to the innermost portion of metal. When the outer layer remains soft, but the inner portion is hardened, this is core hardening.