The rebaseall utility is a convenient way for users that suffer from the Cygwin rebase problem to rebase their entire system (i.e., all of their DLLs). The following is a list of known Cygwin applications that are affected by the rebase problem: Apache Perl Python The rebase problem is due to fork() failing when it is unable to load DLLs in the child at the same address as in the parent. This is caused by DLLs which have conflicting base addresses.