6. Managing Kea with keactrl

6.1. Overview

keactrl is a shell script which controls the startup, shutdown, and reconfiguration of the Kea servers (kea-dhcp4, kea-dhcp6, kea-dhcp-ddns, kea-ctrl-agent, and kea-netconf). It also provides the means for checking the current status of the servers and determining the configuration files in use.

keactrl is available only when Kea is built from sources. When installing Kea using native packages, the native systemd scripts are provided. See Native Packages and systemd Section for details.

6.2. Command Line Options

keactrl is run as follows:

# keactrl <command> [-c keactrl-config-file] [-s server[,server,...]]

<command> is one of the commands described in Commands.

The optional -c keactrl-config-file switch allows specification of an alternate keactrl configuration file. (--ctrl-config is a synonym for -c.) In the absence of -c, keactrl uses the default configuration file [kea-install-dir]/etc/kea/keactrl.conf.

The optional -s server[,server,...] switch selects the servers to which the command is issued. (--server is a synonym for -s.) If absent, the command is sent to all servers enabled in the keactrl configuration file. If multiple servers are specified, they should be separated by commas with no intervening spaces.

6.3. The keactrl Configuration File

Depending on the administrator's requirements, it may not be necessary to run all of the available servers. The keactrl configuration file sets which servers are enabled and which are disabled. The default configuration file is [kea-install-dir]/etc/kea/keactrl.conf, but this can be overridden on a per-command basis using the -c switch.

The contents of keactrl.conf are:

# This is a configuration file for keactrl script which controls
# the startup, shutdown, reconfiguration and gathering the status
# of the Kea processes.

# prefix holds the location where the Kea is installed.
prefix=@prefix@

# Location of Kea configuration file.
kea_dhcp4_config_file=@sysconfdir@/@PACKAGE@/kea-dhcp4.conf
kea_dhcp6_config_file=@sysconfdir@/@PACKAGE@/kea-dhcp6.conf
kea_dhcp_ddns_config_file=@sysconfdir@/@PACKAGE@/kea-dhcp-ddns.conf
kea_ctrl_agent_config_file=@sysconfdir@/@PACKAGE@/kea-ctrl-agent.conf
kea_netconf_config_file=@sysconfdir@/@PACKAGE@/kea-netconf.conf

# Location of Kea binaries.
exec_prefix=@exec_prefix@
dhcp4_srv=@sbindir@/kea-dhcp4
dhcp6_srv=@sbindir@/kea-dhcp6
dhcp_ddns_srv=@sbindir@/kea-dhcp-ddns
ctrl_agent_srv=@sbindir@/kea-ctrl-agent
netconf_srv=@sbindir@/kea-netconf

# Start DHCPv4 server?
dhcp4=yes

# Start DHCPv6 server?
dhcp6=yes

# Start DHCP DDNS server?
dhcp_ddns=no

# Start Control Agent?
ctrl_agent=yes

# Start Netconf?
netconf=no

# Be verbose?
kea_verbose=no

Note

In the example above, strings of the form @something@ are replaced by the appropriate values when Kea is installed.

Setting the dhcp4, dhcp6, dhcp_ddns, ctrl_agent, and netconf parameters set to "yes" configures keactrl to manage (start, reconfigure) all servers, i.e. kea-dhcp4, kea-dhcp6, kea-dhcp-ddns, kea-ctrl-agent, and kea-netconf. When any of these parameters is set to "no", keactrl ignores the corresponding server when starting or reconfiguring Kea. Some daemons (dhcp_ddns and netconf) are disabled by default.

By default, Kea servers managed by keactrl are located in [kea-install-dir]/sbin. This should work for most installations. If the default location needs to be altered, the paths specified with the dhcp4_srv, dhcp6_srv, dhcp_ddns_srv, ctrl_agent_srv, and netconf_srv parameters should be modified.

The kea_verbose parameter specifies the verbosity of the servers being started. When kea_verbose is set to yes, the logging level of the server is set to DEBUG. Modification of the logging severity in a configuration file, as described in Logging, will have no effect as long as kea_verbose is set to "yes." Setting it to "no" causes the server to use the logging levels specified in the Kea configuration file. If no logging configuration is specified, the default settings are used.

Note

The verbosity for the server is set when it is started. Once started, the verbosity can only be changed by stopping the server and starting it again with the new value of the kea_verbose parameter.

6.4. Commands

The following commands are supported by keactrl:

  • start - starts the selected servers.

  • stop - stops all running servers.

  • reload - triggers reconfiguration of the selected servers by sending the SIGHUP signal to them.

  • status - returns the status of the servers (active or inactive) and the names of the configuration files in use.

  • version - prints out the version of the keactrl tool itself, together with the versions of the Kea daemons.

Typical output from keactrl when starting the servers looks similar to the following:

$ keactrl start
INFO/keactrl: Starting kea-dhcp4 -c /usr/local/etc/kea/kea-dhcp4.conf -d
INFO/keactrl: Starting kea-dhcp6 -c /usr/local/etc/kea/kea-dhcp6.conf -d
INFO/keactrl: Starting kea-dhcp-ddns -c /usr/local/etc/kea/kea-dhcp-ddns.conf -d
INFO/keactrl: Starting kea-ctrl-agent -c /usr/local/etc/kea/kea-ctrl-agent.conf -d
INFO/keactrl: Starting kea-netconf -c /usr/local/etc/kea/kea-netconf.conf -d

Kea's servers create PID files upon startup. These files are used by keactrl to determine whether a given server is running. If one or more servers are running when the start command is issued, the output looks similar to the following:

$ keactrl start
INFO/keactrl: kea-dhcp4 appears to be running, see: PID 10918, PID file: /usr/local/var/run/kea/kea.kea-dhcp4.pid.
INFO/keactrl: kea-dhcp6 appears to be running, see: PID 10924, PID file: /usr/local/var/run/kea/kea.kea-dhcp6.pid.
INFO/keactrl: kea-dhcp-ddns appears to be running, see: PID 10930, PID file: /usr/local/var/run/kea/kea.kea-dhcp-ddns.pid.
INFO/keactrl: kea-ctrl-agent appears to be running, see: PID 10931, PID file: /usr/local/var/run/kea/kea.kea-ctrl-agent.pid.
INFO/keactrl: kea-netconf appears to be running, see: PID 10123, PID file: /usr/local/var/run/kea/kea.kea-netconf.pid.

During normal shutdowns, these PID files are deleted; they may, however, be left over as remnants following a system crash. It is possible, though highly unlikely, that upon system restart the PIDs they contain may actually refer to processes unrelated to Kea. This condition will cause keactrl to decide that the servers are running, when in fact they are not. In such a case the PID files listed in the keactrl output must be manually deleted.

The following command stops all servers:

$ keactrl stop
INFO/keactrl: Stopping kea-dhcp4...
INFO/keactrl: Stopping kea-dhcp6...
INFO/keactrl: Stopping kea-dhcp-ddns...
INFO/keactrl: Stopping kea-ctrl-agent...
INFO/keactrl: Stopping kea-netconf...

Note that the stop command attempts to stop all servers regardless of whether they are "enabled" in keactrl.conf. If any of the servers are not running, an informational message is displayed as in the stop command output below.

$ keactrl stop
INFO/keactrl: kea-dhcp4 isn't running.
INFO/keactrl: kea-dhcp6 isn't running.
INFO/keactrl: kea-dhcp-ddns isn't running.
INFO/keactrl: kea-ctrl-agent isn't running.
INFO/keactrl: kea-netconf isn't running.

As already mentioned, the reconfiguration of each Kea server is triggered by the SIGHUP signal. The reload command sends the SIGHUP signal to any servers that are enabled in the keactrl configuration file and that are currently running. When a server receives the SIGHUP signal it rereads its configuration file and, if the new configuration is valid, uses the new configuration. If the new configuration proves to be invalid, the server retains its current configuration; however, in some cases a fatal error message is logged indicating that the server is no longer providing any service: a working configuration must be loaded as soon as possible.

A reload is executed as follows:

$ keactrl reload
INFO/keactrl: Reloading kea-dhcp4...
INFO/keactrl: Reloading kea-dhcp6...
INFO/keactrl: Reloading kea-dhcp-ddns...
INFO/keactrl: Reloading kea-ctrl-agent...

If any of the servers are not running, an informational message is displayed as in the reload command output below. kea-netconf does not support the SIGHUP signal. If its configuration has changed, please stop and restart it for the change to take effect.

$ keactrl stop
INFO/keactrl: kea-dhcp4 isn't running.
INFO/keactrl: kea-dhcp6 isn't running.
INFO/keactrl: kea-dhcp-ddns isn't running.
INFO/keactrl: kea-ctrl-agent isn't running.
INFO/keactrl: kea-netconf isn't running.

Note

NETCONF is an optional feature that is disabled by default and can be enabled during compilation. If Kea was compiled without NETCONF support, keactrl does not provide information about it. The NETCONF entries are still present in the keactrl.conf file, but NETCONF status is not shown and other commands ignore it.

Note

Currently keactrl does not report configuration failures when the server is started or reconfigured. To check if the server's configuration succeeded, the Kea log must be examined for errors. By default, the log is written to the syslog file.

Sometimes it is useful to check which servers are running. The status command reports this, with typical output that looks like:

$ keactrl status
DHCPv4 server: active
DHCPv6 server: inactive
DHCP DDNS: active
Control Agent: active
Netconf agent: inactive
Kea configuration file: /usr/local/etc/kea/kea.conf
Kea DHCPv4 configuration file: /usr/local/etc/kea/kea-dhcp4.conf
Kea DHCPv6 configuration file: /usr/local/etc/kea/kea-dhcp6.conf
Kea DHCP DDNS configuration file: /usr/local/etc/kea/kea-dhcp-ddns.conf
Kea Control Agent configuration file: /usr/local/etc/kea/kea-ctrl-agent.conf
Kea Netconf configuration file: /usr/local/etc/kea/kea-netconf.conf
keactrl configuration file: /usr/local/etc/kea/keactrl.conf

keactrl status offers basic reporting capabilities. For more extensive insight into Kea's health and status, consider deploying Stork. For details, see Monitoring Kea With Stork.

6.5. Overriding the Server Selection

The optional -s switch allows the selection of the server(s) to which the keactrl command is issued. For example, the following instructs keactrl to stop the kea-dhcp4 and kea-dhcp6 servers and leave the kea-dhcp-ddns and kea-ctrl-agent running:

$ keactrl stop -s dhcp4,dhcp6

Similarly, the following starts only the kea-dhcp4 and kea-dhcp-ddns servers, but not kea-dhcp6 or kea-ctrl-agent.

$ keactrl start -s dhcp4,dhcp_ddns

Note that the behavior of the -s switch with the start and reload commands is different from its behavior with the stop command. On start and reload, keactrl checks whether the servers given as parameters to the -s switch are enabled in the keactrl configuration file; if not, the server is ignored. For stop, however, this check is not made; the command is applied to all listed servers, regardless of whether they have been enabled in the file.

The following keywords can be used with the -s command-line option:

6.6. Native Packages and systemd

keactrl is a script that was developed to assist in managing Kea processes. However, all modern operating systems have their own process-management scripts, such as systemd. In general, these native scripts should be used, as they have several advantages. systemd scripts handle processes in a uniform way, so Kea is handled in a similar fashion to HTTP or a mail server. Second and more importantly, systemd allows dependencies to be defined between services. For example, it is easy to specify that the Kea server should not start until the network interfaces are operational. Using native scripts also has other benefits, such as the ability to enable or disable services using commands, and the ability to temporarily start a disabled service.

Thus, it is recommended to use systemctl commands if they are available. Native Kea packages do not provide keactrl; systemctl service definitions are provided instead. Consult the system documentation for details.

Briefly, here are example commands to check status, start, stop, and restart various Kea daemons:

# systemctl status kea-ctrl-agent
# systemctl start kea-dhcp4
# systemctl stop kea-dhcp6
# systemctl restart kea-dhcp-ddns

Note that the service names may be slightly different between Linux distributions; in general, we have followed the naming conventions in third-party packages. In particular, some systems may not have the isc- prefix.