You must have at least 780MB of memory and 1160MB of hard disk space to perform a normal installation. Note that these are fairly minimal numbers. For more realistic figures, see Del 3.4, «Meeting Minimum Hardware Requirements».

The installer normally automatically enables memory-saving tricks to be able to run on such low-memory system, but on architectures that are less tested it may miss doing so. It can however be enabled manually by appending the lowmem=1 or even lowmem=2 boot parameter (see also Del 6.3.1.1, «Check available memory / low memory mode» and Del 5.3.2, «Debian Installer Parameters»).

Installation on systems with less memory^[2] or disk space available may be possible but is only advised for experienced users.