download via svn or svn-lite:
#command to download the complete FreeBSD source-files svnlite checkout https://svn.freebsd.org/base/releng/11.0/ /usr/src/ #command to download only the FreeBSD kernel/header source-files svnlite checkout https://svn.freebsd.org/base/releng/11.0/sys/ /usr/src/sys