ovn-northd(8) OVN Manual ovn-northd(8)
NAME
ovn-northd - Open Virtual Network central control daemon
SYNOPSIS
ovn-northd [options]
DESCRIPTION
ovn-northd is a centralized daemon responsible for translating the
high-level OVN configuration into logical configuration consumable by
daemons such as ovn-controller. It translates the logical network con‐
figuration in terms of conventional network concepts, taken from the
OVN Northbound Database (see ovn-nb(5)), into logical datapath flows in
the OVN Southbound Database (see ovn-sb(5)) below it.
OPTIONS
--ovnnb-db=database
The OVSDB database containing the OVN Northbound Database. If
the OVN_NB_DB environment variable is set, its value is used as
the default. Otherwise, the default is unix:/ovnnb_db.sock.
--ovnsb-db=database
The OVSDB database containing the OVN Southbound Database. If
the OVN_SB_DB environment variable is set, its value is used as
the default. Otherwise, the default is unix:/ovnsb_db.sock.
--dry-run
Causes ovn-northd to start paused. In the paused state,
ovn-northd does not apply any changes to the databases, although
it continues to monitor them. For more information, see the
pause command, under Runtime Management Commands below.
--n-threads=N
In certain situations, it may be desirable to enable paral‐
lelization on a system to decrease latency (at the potential
cost of increasing CPU usage).
This option will cause ovn-northd to use N threads when building
logical flows, when N is within [2-256]. If N is 1, paralleliza‐
tion is disabled (default behavior). If N is less than 1, then N
is set to 1, parallelization is disabled and a warning is
logged. If N is more than 256, then N is set to 256, paral‐
lelization is enabled (with 256 threads) and a warning is
logged.
--dump-inc-proc-graph[=node]
Dump the incremental processing engine graph representation in
DOT format to stdout at startup and then exit. If node is speci‐
fied, only the subgraph rooted at that engine node is printed.
database in the above options must be an OVSDB active or passive con‐
nection method, as described in ovsdb(7).
Daemon Options
--pidfile[=pidfile]
Causes a file (by default, program.pid) to be created indicating
the PID of the running process. If the pidfile argument is not
specified, or if it does not begin with /, then it is created in
.
If --pidfile is not specified, no pidfile is created.
--overwrite-pidfile
By default, when --pidfile is specified and the specified pid‐
file already exists and is locked by a running process, the dae‐
mon refuses to start. Specify --overwrite-pidfile to cause it to
instead overwrite the pidfile.
When --pidfile is not specified, this option has no effect.
--detach
Runs this program as a background process. The process forks,
and in the child it starts a new session, closes the standard
file descriptors (which has the side effect of disabling logging
to the console), and changes its current directory to the root
(unless --no-chdir is specified). After the child completes its
initialization, the parent exits.
--monitor
Creates an additional process to monitor this program. If it
dies due to a signal that indicates a programming error (SIGA‐‐
BRT, SIGALRM, SIGBUS, SIGFPE, SIGILL, SIGPIPE, SIGSEGV, SIGXCPU,
or SIGXFSZ) then the monitor process starts a new copy of it. If
the daemon dies or exits for another reason, the monitor process
exits.
This option is normally used with --detach, but it also func‐
tions without it.
--no-chdir
By default, when --detach is specified, the daemon changes its
current working directory to the root directory after it de‐
taches. Otherwise, invoking the daemon from a carelessly chosen
directory would prevent the administrator from unmounting the
file system that holds that directory.
Specifying --no-chdir suppresses this behavior, preventing the
daemon from changing its current working directory. This may be
useful for collecting core files, since it is common behavior to
write core dumps into the current working directory and the root
directory is not a good directory to use.
This option has no effect when --detach is not specified.
--no-self-confinement
By default this daemon will try to self-confine itself to work
with files under well-known directories determined at build
time. It is better to stick with this default behavior and not
to use this flag unless some other Access Control is used to
confine daemon. Note that in contrast to other access control
implementations that are typically enforced from kernel-space
(e.g. DAC or MAC), self-confinement is imposed from the user-
space daemon itself and hence should not be considered as a full
confinement strategy, but instead should be viewed as an addi‐
tional layer of security.
--user=user:group
Causes this program to run as a different user specified in
user:group, thus dropping most of the root privileges. Short
forms user and :group are also allowed, with current user or
group assumed, respectively. Only daemons started by the root
user accepts this argument.
On Linux, daemons will be granted CAP_IPC_LOCK and
CAP_NET_BIND_SERVICES before dropping root privileges. Daemons
that interact with a datapath, such as ovs-vswitchd, will be
granted three additional capabilities, namely CAP_NET_ADMIN,
CAP_NET_BROADCAST and CAP_NET_RAW. The capability change will
apply even if the new user is root.
Logging Options
-v[spec]
--verbose=[spec]
Sets logging levels. Without any spec, sets the log level for
every module and destination to dbg. Otherwise, spec is a list of
words separated by spaces or commas or colons, up to one from each
category below:
• A valid module name, as displayed by the vlog/list command
on ovs-appctl(8), limits the log level change to the speci‐
fied module.
• syslog, console, or file, to limit the log level change to
only to the system log, to the console, or to a file, re‐
spectively. (If --detach is specified, the daemon closes
its standard file descriptors, so logging to the console
will have no effect.)
• off, emer, err, warn, info, or dbg, to control the log
level. Messages of the given severity or higher will be
logged, and messages of lower severity will be filtered
out. off filters out all messages. See ovs-appctl(8) for a
definition of each log level.
Case is not significant within spec.
Regardless of the log levels set for file, logging to a file will
not take place unless --log-file is also specified (see below).
For compatibility with older versions of OVS, any is accepted as a
word but has no effect.
-v
--verbose
Sets the maximum logging verbosity level, equivalent to --ver‐‐
bose=dbg.
-vPATTERN:destination:pattern
--verbose=PATTERN:destination:pattern
Sets the log pattern for destination to pattern. Refer to ovs-ap‐‐
pctl(8) for a description of the valid syntax for pattern.
-vFACILITY:facility
--verbose=FACILITY:facility
Sets the RFC5424 facility of the log message. facility can be one
of kern, user, mail, daemon, auth, syslog, lpr, news, uucp, clock,
ftp, ntp, audit, alert, clock2, local0, local1, local2, local3,
local4, local5, local6 or local7. If this option is not specified,
daemon is used as the default for the local system syslog and lo‐‐
cal0 is used while sending a message to the target provided via
the --syslog-target option.
--log-file[=file]
Enables logging to a file. If file is specified, then it is used
as the exact name for the log file. The default log file name used
if file is omitted is /usr/local/var/log/ovn/program.log.
--syslog-target=host:port
Send syslog messages to UDP port on host, in addition to the sys‐
tem syslog. The host must be a numerical IP address, not a host‐
name.
--syslog-method=method
Specify method as how syslog messages should be sent to syslog
daemon. The following forms are supported:
• libc, to use the libc syslog() function. Downside of using
this options is that libc adds fixed prefix to every mes‐
sage before it is actually sent to the syslog daemon over
/dev/log UNIX domain socket.
• unix:file, to use a UNIX domain socket directly. It is pos‐
sible to specify arbitrary message format with this option.
However, rsyslogd 8.9 and older versions use hard coded
parser function anyway that limits UNIX domain socket use.
If you want to use arbitrary message format with older
rsyslogd versions, then use UDP socket to localhost IP ad‐
dress instead.
• udp:ip:port, to use a UDP socket. With this method it is
possible to use arbitrary message format also with older
rsyslogd. When sending syslog messages over UDP socket ex‐
tra precaution needs to be taken into account, for example,
syslog daemon needs to be configured to listen on the spec‐
ified UDP port, accidental iptables rules could be inter‐
fering with local syslog traffic and there are some secu‐
rity considerations that apply to UDP sockets, but do not
apply to UNIX domain sockets.
• null, to discard all messages logged to syslog.
The default is taken from the OVS_SYSLOG_METHOD environment vari‐
able; if it is unset, the default is libc.
PKI Options
PKI configuration is required in order to use SSL/TLS for the connec‐
tions to the Northbound and Southbound databases.
-p privkey.pem
--private-key=privkey.pem
Specifies a PEM file containing the private key used as
identity for outgoing SSL/TLS connections.
-c cert.pem
--certificate=cert.pem
Specifies a PEM file containing a certificate that certi‐
fies the private key specified on -p or --private-key to be
trustworthy. The certificate must be signed by the certifi‐
cate authority (CA) that the peer in SSL/TLS connections
will use to verify it.
-C cacert.pem
--ca-cert=cacert.pem
Specifies a PEM file containing the CA certificate for ver‐
ifying certificates presented to this program by SSL/TLS
peers. (This may be the same certificate that SSL/TLS peers
use to verify the certificate specified on -c or --certifi‐‐
cate, or it may be a different one, depending on the PKI
design in use.)
-C none
--ca-cert=none
Disables verification of certificates presented by SSL/TLS
peers. This introduces a security risk, because it means
that certificates cannot be verified to be those of known
trusted hosts.
--ssl-server-name=servername
Specifies the server name to use for TLS Server Name Indi‐
cation (SNI). By default, the hostname from the connection
string is used for SNI. This option allows overriding the
SNI hostname, which is useful when connecting through prox‐
ies or service meshes where the connection endpoint differs
from the intended server name.
Other Options
--unixctl=socket
Sets the name of the control socket on which program listens for
runtime management commands (see RUNTIME MANAGEMENT COMMANDS,
below). If socket does not begin with /, it is interpreted as
relative to . If --unixctl is not used at all, the default
socket is /program.pid.ctl, where pid is program’s process ID.
Specifying none for socket disables the control socket feature.
-h
--help
Prints a brief help message to the console.
-V
--version
Prints version information to the console.
RUNTIME MANAGEMENT COMMANDS
ovn-appctl can send commands to a running ovn-northd process. The cur‐
rently supported commands are described below.
exit Causes ovn-northd to gracefully terminate.
pause Pauses ovn-northd. When it is paused, ovn-northd receives
changes from the Northbound and Southbound database
changes as usual, but it does not send any updates. A
paused ovn-northd also drops database locks, which allows
any other non-paused instance of ovn-northd to take over.
resume Resumes the ovn-northd operation to process Northbound
and Southbound database contents and generate logical
flows. This will also instruct ovn-northd to aspire for
the lock on SB DB.
is-paused
Returns "true" if ovn-northd is currently paused, "false"
otherwise.
status Prints this server’s status. Status will be "active" if
ovn-northd has acquired OVSDB lock on SB DB, "standby" if
it has not or "paused" if this instance is paused.
sb-cluster-state-reset
Reset southbound database cluster status when databases
are destroyed and rebuilt.
If all databases in a clustered southbound database are
removed from disk, then the stored index of all databases
will be reset to zero. This will cause ovn-northd to be
unable to read or write to the southbound database, be‐
cause it will always detect the data as stale. In such a
case, run this command so that ovn-northd will reset its
local index so that it can interact with the southbound
database again.
nb-cluster-state-reset
Reset northbound database cluster status when databases
are destroyed and rebuilt.
This performs the same task as sb-cluster-state-reset ex‐
cept for the northbound database client.
parallel-build/set-n-threads N
Set the number of threads used for building logical
flows. When N is within [2-256], parallelization is en‐
abled. When N is 1 parallelization is disabled. When N is
less than 1 or more than 256, an error is returned. If
ovn-northd fails to start parallelization (e.g. fails to
setup semaphores), parallelization is disabled and an er‐
ror is returned.
parallel-build/get-n-threads
Return the number of threads used for building logical
flows.
nb-connection-status
Prints whether the connection to the OVN Northbound data‐
base is currently connected or not.
sb-connection-status
Prints whether the connection to the OVN Southbound data‐
base is currently connected or not.
debug/chassis-features-list
Lists the chassis feature flags and their current values
as determined by ovn-northd. These features reflect the
capabilities reported by the connected chassis.
inc-engine/show-stats
Display ovn-northd engine counters. For each engine node
the following counters have been added:
• recompute
• compute
• abort
inc-engine/show-stats engine_node_name [counter_name]
Display the ovn-northd engine counter(s) for the speci‐
fied engine_node_name. counter_name is optional and can
be one of recompute, compute or abort.
inc-engine/clear-stats
Reset ovn-northd engine counters.
inc-engine/recompute
Triggers a full recompute of the incremental processing
engine on the next iteration.
inc-engine/compute-log-timeout msecs
Sets the timeout in milliseconds for logging engine com‐
pute events.
inc-engine/list-stopwatches [node]
Lists the engine nodes and their change handler names. If
node is specified, only the handlers for that engine node
are listed.
ACTIVE-STANDBY FOR HIGH AVAILABILITY
You may run ovn-northd more than once in an OVN deployment. When con‐
nected to a standalone or clustered DB setup, OVN will automatically
ensure that only one of them is active at a time. If multiple instances
of ovn-northd are running and the active ovn-northd fails, one of the
hot standby instances of ovn-northd will automatically take over.
Active-Standby with multiple OVN DB servers
You may run multiple OVN DB servers in an OVN deployment with:
• OVN DB servers deployed in active/passive mode with one
active and multiple passive ovsdb-servers.
• ovn-northd also deployed on all these nodes, using unix
ctl sockets to connect to the local OVN DB servers.
In such deployments, the ovn-northds on the passive nodes will process
the DB changes and compute logical flows to be thrown out later, be‐
cause write transactions are not allowed by the passive ovsdb-servers.
It results in unnecessary CPU usage.
With the help of runtime management command pause, you can pause
ovn-northd on these nodes. When a passive node becomes master, you can
use the runtime management command resume to resume the ovn-northd to
process the DB changes.
LOGICAL FLOW TABLE STRUCTURE
For a detailed description of the logical flow tables that ovn-northd
populates in the OVN_Southbound database, including logical switch and
router datapath pipelines and drop sampling behavior, see ovn-logi‐‐
cal-flows(7).
OVN 26.03.90 ovn-northd ovn-northd(8)