sys-umount(2) - Unix First Edition Manual Page
11/3/71SYS_UMOUNT (II)

NAME umount -- dismount file system
SYNOPSIS sys umount; special / umount = 22.; not in assembler
DESCRIPTION umount announces to the system that special file special is no longerto contain a removable file system. The file associated with the

special file reverts to its ordinary interpretation (see mount). The user must take care that all activity on the file system hasceased.

SEE_ALSO mount
DIAGNOSTICS Error bit (c--bit) set if no file system was mounted on the specialfile.

BUGS Use of this call should be restricted to the super--user.
OWNER ken, dmr