Tudo bem, então não tenho certeza de como isso resolveu, mas desinstalar e reinstalar o Postfix conseguiu funcionar.
De alguma forma, eu consegui remover o diretório /var/run/saslauthd durante a instalação da autenticação para o Postfix, então estava tentando apt-get purge e depois reinstalar os vários pacotes saslauthd para regenerar todos os arquivos. No entanto, quando tentei executar o apt-get purge libsasl2-2 sasl2-bin libsasl2-modules , o APT estava tentando remover um monte de pacotes não relacionados, como o Apache e o Git.
root@localhost:~# apt-get purge libsasl2-2 sasl2-bin libsasl2-modules
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
apache2-data apache2-utils bsdtar db-util db5.3-util debugedit fonts-droid-fallback fonts-noto-mono gamin ghostscript git-man imagemagick-common libapr1 libapr1-dev libaprutil1 libaprutil1-dbd-sqlite3 libarchive-tools libarchive13
libconfig-file-perl libcupsfilters1 libcupsimage2 libecap3 liberror-perl libfftw3-double3 libgamin0 libgs9 libgs9-common libijs-0.35 libjbig2dec0 liblqr-1-0 liblua5.1-0 liblzo2-2 libm17n-0 libmagickcore-6.q16-2 libmagickwand-6.q16-2
libminiupnpc10 libnatpmp1 libotf0 libpaper-utils libpaper1 libregexp-assemble-perl librpm3 librpmbuild3 librpmio3 librpmsign3 librtmp1 libsctp-dev libsctp1 libsqlite0 lksctp-tools m17n-db poppler-data python-libxml2 python-lzma
python-rpm python-sqlite python-sqlitecachec python3-xkit rpm rpm-common rpm2cpio ruby-childprocess ruby-domain-name ruby-erubis ruby-ffi ruby-http-cookie ruby-i18n ruby-listen ruby-log4r ruby-mime-types ruby-net-scp ruby-net-sftp
ruby-net-ssh ruby-netrc ruby-nokogiri ruby-pkg-config ruby-rb-inotify ruby-rest-client ruby-sqlite3 ruby-unf ruby-unf-ext spawn-fcgi sqlite3 squid-common squid-langpack transmission-common ubuntu-drivers-common uuid-dev
Use 'apt autoremove' to remove them.
The following packages will be REMOVED:
apache2* apache2-bin* apache2-dev* apt-file* apt-transport-https* curl* dirmngr* emacs24* gconf-service* gconf-service-backend* gconf2* git* libaprutil1-dev* libaprutil1-ldap* libcurl3* libcurl3-gnutls* libcurl4-gnutls-dev*
libldap-2.4-2* libldap2-dev* libsasl2-2* libsasl2-dev* libsasl2-modules* lighttpd* php-elisp* php7.0-curl* postfix* python-apt* python-pycurl* python-software-properties* python-urlgrabber* python3-pycurl*
python3-software-properties* sasl2-bin* software-properties-common* software-properties-gtk* squid* squid3* transmission-cli* vagrant* yum*
0 upgraded, 0 newly installed, 40 to remove and 0 not upgraded.
After this operation, 85.4 MB disk space will be freed.
Do you want to continue? [Y/n]
Estou executando o Ubuntu 16.10.
Como posso corrigir isso?