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Full list of services offered by a default OpenBSD installation

Written by Solène, on 16 February 2021.
Tags: #openbsd69 #openbsd #unix

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Introduction

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, pflogd, sndiod, openssh, ntpd, syslogd and smtpd. Network related daemons smtpd (localhost only), openssh and ntpd (as a client) are running.

Service list

I extracted the list of base install services by looking at /etc/rc.conf.

$ grep _flags /etc/rc.conf | cut -d '_' -f 1

amd

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".

amd man page

apmd

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.

apmd man page

apm man page

bgpd

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.

OpenBGPD website

bootparamd

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

cron

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.

Cron man page

Crontab command

Crontab format

dhcpd

This is a DHCP server used to automatically provide IPv4 addresses on an network for systems using a DHCP client.

dhcrelay

This is a DHCP requests relay, used to on a network interface to relay the requests to another interface.

dvmrpd

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.

eigrpd

This daemon is an Internal gateway link-state routing protocol, it is like OSPF but compatible with CISCO.

ftpd

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).

ftpd man page

ftpproxy

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.

ftpproxy6

Same as above but for IPv6. Using IPv6 behind a NAT make no sense.

hostapd

This is the daemon that turns OpenBSD into a WiFi access point.

hostapd man page

hostapd configuration file man page

hotplugd

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.

hotplugd man page

httpd

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 man page

httpd configuration file man page

identd

Identd is a daemon for the Identification Protocol which returns the login name of an user who initiatied a connection, this can be used on IRC to authenticate which user started an IRC connection.

ifstated

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 man page

ifstated configuration file man page

iked

This daemon is used to provide IKEv2 authentication for IPSec tunnel establishment.

OpenBSD FAQ about VPN

inetd

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.

inetd man page

isakmpd

This daemon is used to provide IKEv1 authentication for IPSec tunnel establishment.

iscsid

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.

ldapd

This is a light LDAP server, offering version 3 of the protocol.

ldap client man page

ldapd daemon man page

ldapd daemon configuration file man page

ldattach

This daemon allows to configure programs that are exposed as a serial port, such as gps devices.

ldomd

This daemon is specific to the sparc64 platform and provide services for dom feature.

lockd

This daemon is used as part of a NFS environment to support file locking.

ldpd

This daemon is used by MPLS routers to get labels.

lpd

This daemon is used to manage print access to a line printer.

mountd

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.

mountd man page

showmount man page

mopd

This daemon is used to distribute MOP images, which seem related to alpha and VAX architectures.

mrouted

Similar to dvmrpd.

nfsd

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.

nfsd man page

nfsstat man page

npppd

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.

nsd

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 man page

nsd configuration file man page

ntpd

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.

ntpd man page

ospfd

It is a daemon for the OSPF routing protocol (Open Shortest Path First).

ospf6d

Same as above for IPv6.

pflogd

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.

pflogd man page

tcpdump

portmap

This daemon is used as part of a NFS environment.

rad

This daemon is used on IPv6 routers to advertise routes so client can automatically pick up routes.

radiusd

This daemon is used to offer RADIUS protocol authentication.

rarpd

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

rbootd

Per the man page, it says « rbootd services boot requests from Hewlett-Packard workstation over LAN ».

relayd

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 man page

relayd control tool man page

relayd configuration file man page

ripd

This is a routing daemon using an old protocol but widely supported.

route6d

Same as above but for IPv6.

sasyncd

This daemon is used to keep IPSec gateways synchronized in case of a fallback required. This can be used with carp devices.

sensorsd

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 man page

sensorsd configuration file man page

slaacd

This service is a daemon that will automatically pick up auto IPv6 configuration on the network.

slowcgi

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.

slowcgi man page

smtpd

This daemon is the SMTP server that will be used to deliver mails locally or to remote email server.

smtpd man page

smtpd configuration file man page

smtpd control command man page

sndiod

This is the daemon handling sound from various sources. It also support sending local sound to a remote sndiod server.

sndiod man page

sndiod control command man page

mixerctl man page to control an audio device

OpenBSD FAQ about multimedia devices

snmpd

This daemon is a SNMP server exposing some system metrics to SNMP client.

snmpd man page

snmpd configuration file man page

spamd

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.

spamlogd

This daemon is dedicated to the update of spamd whitelist.

sshd

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 man page

sshd configuration file man page

statd

This daemon is used in NFS environment using lockd in order to check if remote hosts are still alive.

switchd

This daemon is used to control a switch pseudo device.

switch pseudo device man page

syslogd

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 man page

syslogd configuration file man page

newsyslog man page

logger man page

tftpd

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

tftpproxy

This daemon is used to manipulate the firewall PF to relay TFTP requests to a TFTP server.

unbound

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 man page

unbound configuration file man page

unwind

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 man page

unwind configuration file man page

unwind control command man page

vmd

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 man page

vmd configuration file man page

vmd control command man page

vmm driver man page

OpenBSD FAQ about virtualization

watchdogd

This daemon is used to trigger watchdog timer devices if any.

wsmoused

This daemon is used to provide a mouse support to the console.

xenodm

This daemon is used to start the X server and allow users to authenticate themselves and log in their session.

xenodm man page

ypbind

This daemon is used with a Yellow Page (YP) server to keep and maintain a binding information file.

ypldap

This daemon offers a YP service using a LDAP backend.

ypserv

This daemon is a YP server.