The issue described here has caused problems for me for a long time.
- Small home server running lots of services: amd, apache24, ataidle, cupsd, dbus, delegate, dhcpd, dhcpd6, firewall, gateway, hald, hylafax, inetd, ipv6_gateway, kdm4, moused, mpd, mysql, named, nfs_client, nfs_server, nis_client, nis_server, nis_yppasswdd, ntpd, openvpn, postgresql, powerd, rpc_lockd, rpc_statd, rpcbind, rtadvd, rtsold, rwhod, samba_server, sendmail, squid, sshd, syslogd, winbindd, zfs
- Rather often (estimated 10% of all reboots) one of the daemons using random port numbers chooses one which is later on required by another daemon which needs a well-known port number to operate
- Example today: mountd listens on port 631 which is required by cups, therefore cups does not work
- Example from a few days ago: ypbind listens on 873 which is required by inetd configured to spawn rsync
- Ports should be chosen so as not to cause conflicts
Proposed mitigation measure: Revert to using well-known port numbers for standard system daemons like it was done ages ago.