Installing multiple instances of Phabricator on the same server

Just non-obvious steps listed (with things to replace in uppercase), follow their installation instructions for general setup

Change default database name prefix

Phabricator for some reason is not using schemas to group tables but rather creates gazillion of different databases, all by default have their names prefixed by phabricator_. This can be changed using (note that trailing underscore will be automatically appended):
bin/config set storage.default-namespace YOURPREFIX

Change directory for PID filed

Have each instance keep its PID files in separate dir, default is /var/tmp/phd/pid. This can be changed using
bin/config set phd.pid-directory /var/tmp/OTHERDIR/pid

Change directory for log files

Have each instance keep its log files in separate directory (default being /var/tmp/phd/log):
bin/config set phd.log-directory /var/tmp/OTHERDIR/log

Set cache namespace

Default cache namespace is phabricator, this can be changed using
bin/config set phabricator.cache-namespace NAMESPACE

Don't forget to add line
export PATH="/usr/local/bin:$PATH"
to ssh-hook file, since FreeBSD is installing php in /usr/local/bin (otherwise you might receive error "error: AuthorizedKeysCommand /usr/local/libexec/XXXX failed, status 127")