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This article is about giving a short description of EVERY service available as part of an OpenBSD default installation (= no package installed).
From all this list, the following list is started by default: cron, dhcpleased, pflogd, sndiod, openssh, ntpd, slaacd, resolvd, sshd, spamlogd, syslogd and smtpd. Network related daemons smtpd (localhost only), openssh and ntpd (as a client) are running.
I extracted the list of base install services by looking at /etc/rc.conf.
$ grep _flags /etc/rc.conf | cut -d '_' -f 1
This daemon is used to automatically mount a remote NFS server when someone wants to access it, it can provide a replacement in case the file system is not reachable. More information using "info amd".
This is the daemon responsible for frequency scaling. It is important to run it on workstation and especially on laptop, it can also trigger automatic suspend or hibernate in case of low battery.
This is a BGP daemon that is used by network routers to exchanges about routes with others routers. This is mainly what makes the Internet work, every hosting company announces their IP ranges and how to reach them, in returns they also receive the paths to connect to all others addresses.
This daemon is used for diskless setups on a network, it provides information about the client such as which NFS mount point to use for swap or root devices.
Information about a diskless setup
This is a daemon that will read from each user cron tabs and the system crontabs to run scheduled commands. User cron tabs are modified using crontab command.
This is a DHCP server used to automatically provide IPv4 addresses on an network for systems using a DHCP client.
This is the new default DHCPv4 client service. It monitors multiples interfaces and is able to handle more complicated setup than dhclient.
This is a DHCP requests relay, used to on a network interface to relay the requests to another interface.
This daemon is a multicast routing daemon, in case you need multicast spanning to deploy it outside of your local LAN. This is mostly replaced by PIM nowadays.
This daemon is an Internal gateway link-state routing protocol, it is like OSPF but compatible with CISCO.
This is a FTP server providing many features. While FTP is getting abandoned and obsolete (certainly because it doesn't really play well with NAT) it could be used to provide read/write anonymous access on a directory (and many other things).
This is a FTP proxy daemon that one is supposed to run on a NAT system, this will automatically add PF rules to connect an incoming request to the server behind the NAT. This is part of the FTP madness.
Same as above but for IPv6. Using IPv6 behind a NAT make no sense.
This is the daemon that turns OpenBSD into a WiFi access point.
hostapd configuration file man page
hotplugd is an amazing daemon that will trigger actions when devices are connected or disconnected. This could be scripted to automatically run a backup if some conditions are met like an usb disk inserted matching a known name or mounting a drive.
httpd is a HTTP(s) daemon which supports a few features like fastcgi support, rewrite and SNI. While it doesn't have all the features a web server like nginx has, it is able to host some PHP programs such as nextcloud, roundcube mail or mediawiki.
httpd configuration file man page
Identd is a daemon for the Identification Protocol which returns the login name of a user who initiatied a connection, this can be used on IRC to authenticate which user started an IRC connection.
This is a daemon monitoring the state of network interfaces and which can take actions upon changes. This can be used to trigger changes in case of an interface losing connectivity. I used it to trigger a route change to a 4G device in case a ping over uplink interface was failing.
ifstated configuration file man page
This daemon is used to provide IKEv2 authentication for IPSec tunnel establishment.
This daemon is often forgotten but is very useful. Inetd can listen on TCP or UDP port and will run a command upon connection on the related port, incoming data will be passed as standard input of the program and program standard output will be returned to the client. This is an easy way to turn a program into a network program, it is not widely used because it doesn't scale well as the whole process of running a new program upon every connection can push a system to its limit.
This daemon is used to provide IKEv1 authentication for IPSec tunnel establishment.
This daemon is an iSCSI initator which will connect to an iSCSI target (let's call it a network block device) and expose it locally as a /dev/vcsi device. OpenBSD doesn't provide a target iSCSI daemon in its base system but there is one in ports.
This is a light LDAP server, offering version 3 of the protocol.
ldapd daemon configuration file man page
This daemon allows to configure programs that are exposed as a serial port, such as gps devices.
This daemon is specific to the sparc64 platform and provide services for dom feature.
This daemon is used as part of a NFS environment to support file locking.
This daemon is used by MPLS routers to get labels.
This daemon is used to manage print access to a line printer.
This daemon is used by remote NFS client to give them information about what the system is currently offering. The command showmount can be used to see what mountd is currently exposing.
This daemon is used to distribute MOP images, which seem related to alpha and VAX architectures.
Similar to dvmrpd.
This server is used to service the NFS requests from NFS client. Statistics about NFS (client or server) can be obtained from the nfsstat command.
This daemon is used to establish connection using PPP but also to create tunnels with L2TP, PPTP and PPPoE. PPP is used by some modems to connect to the Internet.
This daemon is an authoritative DNS nameserver, which mean it is holding all information about a domain name and about the subdomains. It receive queries from recursive servers such as unbound / unwind etc... If you own a domain name and you want to manage it from your system, this is what you want.
nsd configuration file man page
This daemon is a NTP service that keep the system clock at the correct time, it can use ntp servers or sensors (like GPS) as time source but also support using remote servers to challenge the time sources. It can acts a daemon to provide time to other NTP client.
It is a daemon for the OSPF routing protocol (Open Shortest Path First).
Same as above for IPv6.
This daemon is receiving packets from PF matching rules with a "log" keyword and will store the data into a logfile that can be reused with tcpdump later. Every packet in the logfile contains information about which rule triggered it so it is very practical for analysis.
This daemon is used as part of a NFS environment.
This daemon is used on IPv6 routers to advertise routes so client can automatically pick up routes.
This daemon is used to offer RADIUS protocol authentication.
This daemon is used for diskless setups in which it will help associating an ARP address to an IP and hostname.
Information about a diskless setup
Per the man page, it says « rbootd services boot requests from Hewlett-Packard workstation over LAN ».
This daemon is used to accept incoming connections and distribute them to backend. It supports many protocols and can act transparently, its purpose is to have a front end that will dispatch connections to a list of backend but also verify backend status. It has many uses and can also be used in addition to httpd to add HTTP headers to a request, or apply conditions on HTTP request headers to choose a backend.
relayd configuration file man page
This daemon is used to manipulate the file /etc/resolv.conf depending on multiple factors like configured DNS or stragegy change in unwind.
This is a routing daemon using an old protocol but widely supported.
Same as above but for IPv6.
This daemon is used to keep IPSec gateways synchronized in case of a fallback required. This can be used with carp devices.
This daemon gathers monitoring information from the hardware like temperature or disk status. If a check exceeds a threshold, a command can be run.
sensorsd configuration file man page
This service is a daemon that will automatically pick up auto IPv6 configuration on the network.
This daemon is used to expose a CGI program as a fastcgi service, allowing httpd HTTP server to run CGI. This is an equivalent of inetd but for fastcgi.
This daemon is the SMTP server that will be used to deliver mails locally or to remote email server.
smtpd configuration file man page
smtpd control command man page
This is the daemon handling sound from various sources. It also support sending local sound to a remote sndiod server.
sndiod control command man page
mixerctl man page to control an audio device
OpenBSD FAQ about multimedia devices
This daemon is a SNMP server exposing some system metrics to SNMP client.
snmpd configuration file man page
This daemon acts as a fake server that will delay or block or pass emails depending on some rules. This can be used to add IP to a block list if they try to send an email to a specific address (like a honeypot), pass emails from servers within an accept list or delay connections for unknown servers (grey list) to make them and reconnect a few times before passing the email to the SMTP server. This is a quite effective way to prevent spam but it becomes less relevant as sender use whole ranges of IP to send emails, meaning that if you want to receive an email from a big email server, you will block server X.Y.Z.1 but then X.Y.Z.2 will retry and so on, so none will pass the grey list.
This daemon is dedicated to the update of spamd whitelist.
This is the well known ssh server. Allow secure connections to a shell from remote client. It has many features that would gain from being more well known, such as restrict commands per public key in the ~/.ssh/authorized_keys files or SFTP only chrooted accesses.
sshd configuration file man page
This daemon is used in NFS environment using lockd in order to check if remote hosts are still alive.
This daemon is used to control a switch pseudo device.
This is the logging server that receives messages from local programs and store them in the according logfile. It can be configured to pipe some messages to command, program like sshlockout uses this method to learn about IP that must be blocked, but can also listen on the network to aggregates logs from other machines. The program newsyslog is used to rotate files (move a file, compress it and allow a new file to be created and remove too old archives). Script can use the command logger to send text to syslog.
syslogd configuration file man page
This daemon is a TFTP server, used to provide kernels over the network for diskless machines or push files to appliances.
Information about a diskless setup
This daemon is used to manipulate the firewall PF to relay TFTP requests to a TFTP server.
This daemon is a recursive DNS server, this is the kind of server listed in /etc/resolv.conf whose responsibility is to translate a fully qualified domain name into the IP address behind, asking one server at a time, for example, to ask www.dataswamp.org server, it is required to ask the .org authoritative server where is the authoritative server for dataswamp (within .org top domain), then dataswamp.org DNS server will be asked what is the address of www.dataswamp.org. It can also keep queries in cache and validates the queries and replies, it is a good idea to have such a server on a LAN with many client to share the queries cache.
unbound configuration file man page
This daemon is a local recursive DNS server that will make its best to give valid replies, it is designed for nomad users that may encounter hostile environments like captive portals or dhcp offered DNS server preventing DNSSEC to work etc.. Unwind polls a few DNS sources (recursive from root servers, provided by dns, stub or DNS over TLS server from configuration file) regularly and choose the fastest. It will also act as a local cache and can't listen on the network to be used by other clients. It also supports a list of blocked domains as input.
unwind configuration file man page
unwind control command man page
This is the daemon that allow to run virtual machines using vmm. As of OpenBSD 6.9 it is capable of running OpenBSD and Linux guests without graphical interface and only one core.
vmd configuration file man page
OpenBSD FAQ about virtualization
This daemon is used to trigger watchdog timer devices if any.
This daemon is used to provide a mouse support to the console.
This daemon is used to start the X server and allow users to authenticate themselves and log in their session.
This daemon is used with a Yellow Page (YP) server to keep and maintain a binding information file.
This daemon offers a YP service using a LDAP backend.
This daemon is a YP server.