zabbix-5.0.19/conf/zabbix_proxy.conf

# This is a configuration file for Zabbix proxy daemon
# To get more information about Zabbix, visit http://www.zabbix.com

############ GENERAL PARAMETERS #################

### Option: ProxyMode
#	Proxy operating mode.
#	0 - proxy in the active mode
#	1 - proxy in the passive mode
#
# Mandatory: no
# Default:
# ProxyMode=0

### Option: Server
#	If ProxyMode is set to active mode:
#		IP address or DNS name of Zabbix server to get configuration data from and send data to.
#	If ProxyMode is set to passive mode:
#		List of comma delimited IP addresses, optionally in CIDR notation, or DNS names of Zabbix server.
#		Incoming connections will be accepted only from the addresses listed here.
#		If IPv6 support is enabled then '127.0.0.1', '::127.0.0.1', '::ffff:127.0.0.1' are treated equally
#		and '::/0' will allow any IPv4 or IPv6 address.
#		'0.0.0.0/0' can be used to allow any IPv4 address.
#		Example: Server=127.0.0.1,192.168.1.0/24,::1,2001:db8::/32,zabbix.example.com
#
# Mandatory: yes
# Default:
# Server=

Server=127.0.0.1

### Option: ServerPort
#	Port of Zabbix trapper on Zabbix server.
#	For a proxy in the passive mode this parameter will be ignored.
#
# Mandatory: no
# Range: 1024-32767
# Default:
# ServerPort=10051

### Option: Hostname
#	Unique, case sensitive Proxy name. Make sure the Proxy name is known to the server!
#	Value is acquired from HostnameItem if undefined.
#
# Mandatory: no
# Default:
# Hostname=

Hostname=Zabbix proxy

### Option: HostnameItem
#	Item used for generating Hostname if it is undefined.
#	Ignored if Hostname is defined.
#
# Mandatory: no
# Default:
# HostnameItem=system.hostname

### Option: ListenPort
#	Listen port for trapper.
#
# Mandatory: no
# Range: 1024-32767
# Default:
# ListenPort=10051

### Option: SourceIP
#	Source IP address for outgoing connections.
#
# Mandatory: no
# Default:
# SourceIP=

### Option: LogType
#	Specifies where log messages are written to:
#		system  - syslog
#		file    - file specified with LogFile parameter
#		console - standard output
#
# Mandatory: no
# Default:
# LogType=file

### Option: LogFile
#	Log file name for LogType 'file' parameter.
#
# Mandatory: yes, if LogType is set to file, otherwise no
# Default:
# LogFile=

LogFile=/tmp/zabbix_proxy.log

### Option: LogFileSize
#	Maximum size of log file in MB.
#	0 - disable automatic log rotation.
#
# Mandatory: no
# Range: 0-1024
# Default:
# LogFileSize=1

### Option: DebugLevel
#	Specifies debug level:
#	0 - basic information about starting and stopping of Zabbix processes
#	1 - critical information
#	2 - error information
#	3 - warnings
#	4 - for debugging (produces lots of information)
#	5 - extended debugging (produces even more information)
#
# Mandatory: no
# Range: 0-5
# Default:
# DebugLevel=3

### Option: EnableRemoteCommands
#		Whether remote commands from Zabbix server are allowed.
#		0 - not allowed
#		1 - allowed
#
# Mandatory: no
# Default:
# EnableRemoteCommands=0

### Option: LogRemoteCommands
#		Enable logging of executed shell commands as warnings.
#		0 - disabled
#		1 - enabled
#
# Mandatory: no
# Default:
# LogRemoteCommands=0

### Option: PidFile
#	Name of PID file.
#
# Mandatory: no
# Default:
# PidFile=/tmp/zabbix_proxy.pid

### Option: SocketDir
#	IPC socket directory.
#		Directory to store IPC sockets used by internal Zabbix services.
#
# Mandatory: no
# Default:
# SocketDir=/tmp

### Option: DBHost
#	Database host name.
#	If set to localhost, socket is used for MySQL.
#	If set to empty string, socket is used for PostgreSQL.
#
# Mandatory: no
# Default:
# DBHost=localhost

### Option: DBName
#	Database name.
#	For SQLite3 path to database file must be provided. DBUser and DBPassword are ignored.
#	Warning: do not attempt to use the same database Zabbix server is using.
#
# Mandatory: yes
# Default:
# DBName=

DBName=zabbix_proxy

### Option: DBSchema
#	Schema name. Used for PostgreSQL.
#
# Mandatory: no
# Default:
# DBSchema=

### Option: DBUser
#	Database user. Ignored for SQLite.
#
# Default:
# DBUser=

DBUser=zabbix

### Option: DBPassword
#	Database password. Ignored for SQLite.
#	Comment this line if no password is used.
#
# Mandatory: no
# Default:
# DBPassword=

### Option: DBSocket
#	Path to MySQL socket.
#
# Mandatory: no
# Default:
# DBSocket=

# Option: DBPort
#	Database port when not using local socket. Ignored for SQLite.
#
# Mandatory: no
# Default:
# DBPort=

######### PROXY SPECIFIC PARAMETERS #############

### Option: ProxyLocalBuffer
#	Proxy will keep data locally for N hours, even if the data have already been synced with the server.
#	This parameter may be used if local data will be used by third party applications.
#
# Mandatory: no
# Range: 0-720
# Default:
# ProxyLocalBuffer=0

### Option: ProxyOfflineBuffer
#	Proxy will keep data for N hours in case if no connectivity with Zabbix Server.
#	Older data will be lost.
#
# Mandatory: no
# Range: 1-720
# Default:
# ProxyOfflineBuffer=1

### Option: HeartbeatFrequency
#	Frequency of heartbeat messages in seconds.
#	Used for monitoring availability of Proxy on server side.
#	0 - heartbeat messages disabled.
#	For a proxy in the passive mode this parameter will be ignored.
#
# Mandatory: no
# Range: 0-3600
# Default:
# HeartbeatFrequency=60

### Option: ConfigFrequency
#	How often proxy retrieves configuration data from Zabbix Server in seconds.
#	For a proxy in the passive mode this parameter will be ignored.
#
# Mandatory: no
# Range: 1-3600*24*7
# Default:
# ConfigFrequency=3600

### Option: DataSenderFrequency
#	Proxy will send collected data to the Server every N seconds.
#	For a proxy in the passive mode this parameter will be ignored.
#
# Mandatory: no
# Range: 1-3600
# Default:
# DataSenderFrequency=1

############ ADVANCED PARAMETERS ################

### Option: StartPollers
#	Number of pre-forked instances of pollers.
#
# Mandatory: no
# Range: 0-1000
# Default:
# StartPollers=5

### Option: StartIPMIPollers
#	Number of pre-forked instances of IPMI pollers.
#		The IPMI manager process is automatically started when at least one IPMI poller is started.
#
# Mandatory: no
# Range: 0-1000
# Default:
# StartIPMIPollers=0

### Option: StartPreprocessors
#	Number of pre-forked instances of preprocessing workers.
#		The preprocessing manager process is automatically started when preprocessor worker is started.
#
# Mandatory: no
# Range: 1-1000
# Default:
# StartPreprocessors=3

### Option: StartPollersUnreachable
#	Number of pre-forked instances of pollers for unreachable hosts (including IPMI and Java).
#	At least one poller for unreachable hosts must be running if regular, IPMI or Java pollers
#	are started.
#
# Mandatory: no
# Range: 0-1000
# Default:
# StartPollersUnreachable=1

### Option: StartTrappers
#	Number of pre-forked instances of trappers.
#	Trappers accept incoming connections from Zabbix sender and active agents.
#
# Mandatory: no
# Range: 0-1000
# Default:
# StartTrappers=5

### Option: StartPingers
#	Number of pre-forked instances of ICMP pingers.
#
# Mandatory: no
# Range: 0-1000
# Default:
# StartPingers=1

### Option: StartDiscoverers
#	Number of pre-forked instances of discoverers.
#
# Mandatory: no
# Range: 0-250
# Default:
# StartDiscoverers=1

### Option: StartHTTPPollers
#	Number of pre-forked instances of HTTP pollers.
#
# Mandatory: no
# Range: 0-1000
# Default:
# StartHTTPPollers=1

### Option: JavaGateway
#	IP address (or hostname) of Zabbix Java gateway.
#	Only required if Java pollers are started.
#
# Mandatory: no
# Default:
# JavaGateway=

### Option: JavaGatewayPort
#	Port that Zabbix Java gateway listens on.
#
# Mandatory: no
# Range: 1024-32767
# Default:
# JavaGatewayPort=10052

### Option: StartJavaPollers
#	Number of pre-forked instances of Java pollers.
#
# Mandatory: no
# Range: 0-1000
# Default:
# StartJavaPollers=0

### Option: StartVMwareCollectors
#	Number of pre-forked vmware collector instances.
#
# Mandatory: no
# Range: 0-250
# Default:
# StartVMwareCollectors=0

### Option: VMwareFrequency
#	How often Zabbix will connect to VMware service to obtain a new data.
#
# Mandatory: no
# Range: 10-86400
# Default:
# VMwareFrequency=60

### Option: VMwarePerfFrequency
#	How often Zabbix will connect to VMware service to obtain performance data.
#
# Mandatory: no
# Range: 10-86400
# Default:
# VMwarePerfFrequency=60

### Option: VMwareCacheSize
#	Size of VMware cache, in bytes.
#	Shared memory size for storing VMware data.
#	Only used if VMware collectors are started.
#
# Mandatory: no
# Range: 256K-2G
# Default:
# VMwareCacheSize=8M

### Option: VMwareTimeout
#	Specifies how many seconds vmware collector waits for response from VMware service.
#
# Mandatory: no
# Range: 1-300
# Default:
# VMwareTimeout=10

### Option: SNMPTrapperFile
#	Temporary file used for passing data from SNMP trap daemon to the proxy.
#	Must be the same as in zabbix_trap_receiver.pl or SNMPTT configuration file.
#
# Mandatory: no
# Default:
# SNMPTrapperFile=/tmp/zabbix_traps.tmp

### Option: StartSNMPTrapper
#	If 1, SNMP trapper process is started.
#
# Mandatory: no
# Range: 0-1
# Default:
# StartSNMPTrapper=0

### Option: ListenIP
#	List of comma delimited IP addresses that the trapper should listen on.
#	Trapper will listen on all network interfaces if this parameter is missing.
#
# Mandatory: no
# Default:
# ListenIP=0.0.0.0

### Option: HousekeepingFrequency
#	How often Zabbix will perform housekeeping procedure (in hours).
#	Housekeeping is removing outdated information from the database.
#	To prevent Housekeeper from being overloaded, no more than 4 times HousekeepingFrequency
#	hours of outdated information are deleted in one housekeeping cycle.
#	To lower load on proxy startup housekeeping is postponed for 30 minutes after proxy start.
#	With HousekeepingFrequency=0 the housekeeper can be only executed using the runtime control option.
#	In this case the period of outdated information deleted in one housekeeping cycle is 4 times the
#	period since the last housekeeping cycle, but not less than 4 hours and not greater than 4 days.
#
# Mandatory: no
# Range: 0-24
# Default:
# HousekeepingFrequency=1

### Option: CacheSize
#	Size of configuration cache, in bytes.
#	Shared memory size, for storing hosts and items data.
#
# Mandatory: no
# Range: 128K-64G
# Default:
# CacheSize=8M

### Option: StartDBSyncers
#	Number of pre-forked instances of DB Syncers.
#
# Mandatory: no
# Range: 1-100
# Default:
# StartDBSyncers=4

### Option: HistoryCacheSize
#	Size of history cache, in bytes.
#	Shared memory size for storing history data.
#
# Mandatory: no
# Range: 128K-2G
# Default:
# HistoryCacheSize=16M

### Option: HistoryIndexCacheSize
#	Size of history index cache, in bytes.
#	Shared memory size for indexing history cache.
#
# Mandatory: no
# Range: 128K-2G
# Default:
# HistoryIndexCacheSize=4M

### Option: Timeout
#	Specifies how long we wait for agent, SNMP device or external check (in seconds).
#
# Mandatory: no
# Range: 1-30
# Default:
# Timeout=3

Timeout=4

### Option: TrapperTimeout
#	Specifies how many seconds trapper may spend processing new data.
#
# Mandatory: no
# Range: 1-300
# Default:
# TrapperTimeout=300

### Option: UnreachablePeriod
#	After how many seconds of unreachability treat a host as unavailable.
#
# Mandatory: no
# Range: 1-3600
# Default:
# UnreachablePeriod=45

### Option: UnavailableDelay
#	How often host is checked for availability during the unavailability period, in seconds.
#
# Mandatory: no
# Range: 1-3600
# Default:
# UnavailableDelay=60

### Option: UnreachableDelay
#	How often host is checked for availability during the unreachability period, in seconds.
#
# Mandatory: no
# Range: 1-3600
# Default:
# UnreachableDelay=15

### Option: ExternalScripts
#	Full path to location of external scripts.
#	Default depends on compilation options.
#	To see the default path run command "zabbix_proxy --help".
#
# Mandatory: no
# Default:
# ExternalScripts=${datadir}/zabbix/externalscripts

### Option: FpingLocation
#	Location of fping.
#	Make sure that fping binary has root ownership and SUID flag set.
#
# Mandatory: no
# Default:
# FpingLocation=/usr/local/sbin/fping

### Option: Fping6Location
#	Location of fping6.
#	Make sure that fping6 binary has root ownership and SUID flag set.
#	Make empty if your fping utility is capable to process IPv6 addresses.
#
# Mandatory: no
# Default:
# Fping6Location=/usr/local/sbin/fping6

### Option: SSHKeyLocation
#	Location of public and private keys for SSH checks and actions.
#
# Mandatory: no
# Default:
# SSHKeyLocation=

### Option: LogSlowQueries
#	How long a database query may take before being logged (in milliseconds).
#	Only works if DebugLevel set to 3 or 4.
#	0 - don't log slow queries.
#
# Mandatory: no
# Range: 1-3600000
# Default:
# LogSlowQueries=0

LogSlowQueries=3000

### Option: TmpDir
#	Temporary directory.
#
# Mandatory: no
# Default:
# TmpDir=/tmp

### Option: AllowRoot
#	Allow the proxy to run as 'root'. If disabled and the proxy is started by 'root', the proxy
#	will try to switch to the user specified by the User configuration option instead.
#	Has no effect if started under a regular user.
#	0 - do not allow
#	1 - allow
#
# Mandatory: no
# Default:
# AllowRoot=0

### Option: User
#	Drop privileges to a specific, existing user on the system.
#	Only has effect if run as 'root' and AllowRoot is disabled.
#
# Mandatory: no
# Default:
# User=zabbix

### Option: Include
#	You may include individual files or all files in a directory in the configuration file.
#	Installing Zabbix will create include directory in /usr/local/etc/zabbix5, unless modified during the compile time.
#
# Mandatory: no
# Default:
# Include=

# Include=/usr/local/etc/zabbix5/zabbix_proxy.general.conf
# Include=/usr/local/etc/zabbix5/zabbix_proxy.conf.d/
# Include=/usr/local/etc/zabbix5/zabbix_proxy.conf.d/*.conf

### Option: SSLCertLocation
#	Location of SSL client certificates.
#	This parameter is used only in web monitoring.
#	Default depends on compilation options.
#	To see the default path run command "zabbix_proxy --help".
#
# Mandatory: no
# Default:
# SSLCertLocation=${datadir}/zabbix/ssl/certs

### Option: SSLKeyLocation
#	Location of private keys for SSL client certificates.
#	This parameter is used only in web monitoring.
#	Default depends on compilation options.
#	To see the default path run command "zabbix_proxy --help".
#
# Mandatory: no
# Default:
# SSLKeyLocation=${datadir}/zabbix/ssl/keys

### Option: SSLCALocation
#	Location of certificate authority (CA) files for SSL server certificate verification.
#	If not set, system-wide directory will be used.
#	This parameter is used only in web monitoring.
#
# Mandatory: no
# Default:
# SSLCALocation=

####### LOADABLE MODULES #######

### Option: LoadModulePath
#	Full path to location of proxy modules.
#	Default depends on compilation options.
#	To see the default path run command "zabbix_proxy --help".
#
# Mandatory: no
# Default:
# LoadModulePath=${libdir}/modules

### Option: LoadModule
#	Module to load at proxy startup. Modules are used to extend functionality of the proxy.
#	Formats:
#		LoadModule=<module.so>
#		LoadModule=<path/module.so>
#		LoadModule=</abs_path/module.so>
#	Either the module must be located in directory specified by LoadModulePath or the path must precede the module name.
#	If the preceding path is absolute (starts with '/') then LoadModulePath is ignored.
#	It is allowed to include multiple LoadModule parameters.
#
# Mandatory: no
# Default:
# LoadModule=

### Option: StatsAllowedIP
#	List of comma delimited IP addresses, optionally in CIDR notation, or DNS names of external Zabbix instances.
#	Stats request will be accepted only from the addresses listed here. If this parameter is not set no stats requests
#	will be accepted.
#	If IPv6 support is enabled then '127.0.0.1', '::127.0.0.1', '::ffff:127.0.0.1' are treated equally
#	and '::/0' will allow any IPv4 or IPv6 address.
#	'0.0.0.0/0' can be used to allow any IPv4 address.
#	Example: StatsAllowedIP=127.0.0.1,192.168.1.0/24,::1,2001:db8::/32,zabbix.example.com
#
# Mandatory: no
# Default:
# StatsAllowedIP=
StatsAllowedIP=127.0.0.1

####### TLS-RELATED PARAMETERS #######

### Option: TLSConnect
#	How the proxy should connect to Zabbix server. Used for an active proxy, ignored on a passive proxy.
#	Only one value can be specified:
#		unencrypted - connect without encryption
#		psk         - connect using TLS and a pre-shared key
#		cert        - connect using TLS and a certificate
#
# Mandatory: yes, if TLS certificate or PSK parameters are defined (even for 'unencrypted' connection)
# Default:
# TLSConnect=unencrypted

### Option: TLSAccept
#	What incoming connections to accept from Zabbix server. Used for a passive proxy, ignored on an active proxy.
#	Multiple values can be specified, separated by comma:
#		unencrypted - accept connections without encryption
#		psk         - accept connections secured with TLS and a pre-shared key
#		cert        - accept connections secured with TLS and a certificate
#
# Mandatory: yes, if TLS certificate or PSK parameters are defined (even for 'unencrypted' connection)
# Default:
# TLSAccept=unencrypted

### Option: TLSCAFile
#	Full pathname of a file containing the top-level CA(s) certificates for
#	peer certificate verification.
#
# Mandatory: no
# Default:
# TLSCAFile=

### Option: TLSCRLFile
#	Full pathname of a file containing revoked certificates.
#
# Mandatory: no
# Default:
# TLSCRLFile=

### Option: TLSServerCertIssuer
#		Allowed server certificate issuer.
#
# Mandatory: no
# Default:
# TLSServerCertIssuer=

### Option: TLSServerCertSubject
#		Allowed server certificate subject.
#
# Mandatory: no
# Default:
# TLSServerCertSubject=

### Option: TLSCertFile
#	Full pathname of a file containing the proxy certificate or certificate chain.
#
# Mandatory: no
# Default:
# TLSCertFile=

### Option: TLSKeyFile
#	Full pathname of a file containing the proxy private key.
#
# Mandatory: no
# Default:
# TLSKeyFile=

### Option: TLSPSKIdentity
#	Unique, case sensitive string used to identify the pre-shared key.
#
# Mandatory: no
# Default:
# TLSPSKIdentity=

### Option: TLSPSKFile
#	Full pathname of a file containing the pre-shared key.
#
# Mandatory: no
# Default:
# TLSPSKFile=

####### For advanced users - TLS ciphersuite selection criteria #######

### Option: TLSCipherCert13
#	Cipher string for OpenSSL 1.1.1 or newer in TLS 1.3.
#	Override the default ciphersuite selection criteria for certificate-based encryption.
#
# Mandatory: no
# Default:
# TLSCipherCert13=

### Option: TLSCipherCert
#	GnuTLS priority string or OpenSSL (TLS 1.2) cipher string.
#	Override the default ciphersuite selection criteria for certificate-based encryption.
#	Example for GnuTLS:
#		NONE:+VERS-TLS1.2:+ECDHE-RSA:+RSA:+AES-128-GCM:+AES-128-CBC:+AEAD:+SHA256:+SHA1:+CURVE-ALL:+COMP-NULL:+SIGN-ALL:+CTYPE-X.509
#	Example for OpenSSL:
#		EECDH+aRSA+AES128:RSA+aRSA+AES128
#
# Mandatory: no
# Default:
# TLSCipherCert=

### Option: TLSCipherPSK13
#	Cipher string for OpenSSL 1.1.1 or newer in TLS 1.3.
#	Override the default ciphersuite selection criteria for PSK-based encryption.
#	Example:
#		TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
#
# Mandatory: no
# Default:
# TLSCipherPSK13=

### Option: TLSCipherPSK
#	GnuTLS priority string or OpenSSL (TLS 1.2) cipher string.
#	Override the default ciphersuite selection criteria for PSK-based encryption.
#	Example for GnuTLS:
#		NONE:+VERS-TLS1.2:+ECDHE-PSK:+PSK:+AES-128-GCM:+AES-128-CBC:+AEAD:+SHA256:+SHA1:+CURVE-ALL:+COMP-NULL:+SIGN-ALL
#	Example for OpenSSL:
#		kECDHEPSK+AES128:kPSK+AES128
#
# Mandatory: no
# Default:
# TLSCipherPSK=

### Option: TLSCipherAll13
#	Cipher string for OpenSSL 1.1.1 or newer in TLS 1.3.
#	Override the default ciphersuite selection criteria for certificate- and PSK-based encryption.
#	Example:
#		TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
#
# Mandatory: no
# Default:
# TLSCipherAll13=

### Option: TLSCipherAll
#	GnuTLS priority string or OpenSSL (TLS 1.2) cipher string.
#	Override the default ciphersuite selection criteria for certificate- and PSK-based encryption.
#	Example for GnuTLS:
#		NONE:+VERS-TLS1.2:+ECDHE-RSA:+RSA:+ECDHE-PSK:+PSK:+AES-128-GCM:+AES-128-CBC:+AEAD:+SHA256:+SHA1:+CURVE-ALL:+COMP-NULL:+SIGN-ALL:+CTYPE-X.509
#	Example for OpenSSL:
#		EECDH+aRSA+AES128:RSA+aRSA+AES128:kECDHEPSK+AES128:kPSK+AES128
#
# Mandatory: no
# Default:
# TLSCipherAll=

### Option: DBTLSConnect
#	Setting this option enforces to use TLS connection to database.
#	required    - connect using TLS
#	verify_ca   - connect using TLS and verify certificate
#	verify_full - connect using TLS, verify certificate and verify that database identity specified by DBHost
#	              matches its certificate
#	On MySQL starting from 5.7.11 and PostgreSQL following values are supported: "required", "verify_ca" and
#	"verify_full".
#	On MariaDB starting from version 10.2.6 "required" and "verify_full" values are supported.
#	Default is not to set any option and behavior depends on database configuration
#
# Mandatory: no
# Default:
# DBTLSConnect=

### Option: DBTLSCAFile
#	Full pathname of a file containing the top-level CA(s) certificates for database certificate verification.
#	Supported only for MySQL and PostgreSQL
#
# Mandatory: no
#	(yes, if DBTLSConnect set to one of: verify_ca, verify_full)
# Default:
# DBTLSCAFile=

### Option: DBTLSCertFile
#	Full pathname of file containing Zabbix proxy certificate for authenticating to database.
#	Supported only for MySQL and PostgreSQL
#
# Mandatory: no
# Default:
# DBTLSCertFile=

### Option: DBTLSKeyFile
#	Full pathname of file containing the private key for authenticating to database.
#	Supported only for MySQL and PostgreSQL
#
# Mandatory: no
# Default:
# DBTLSKeyFile=

### Option: DBTLSCipher
#	The list of encryption ciphers that Zabbix proxy permits for TLS protocols up through TLSv1.2
#	Supported only for MySQL
#
# Mandatory no
# Default:
# DBTLSCipher=

### Option: DBTLSCipher13
#	The list of encryption ciphersuites that Zabbix proxy permits for TLSv1.3 protocol
#	Supported only for MySQL, starting from version 8.0.16
#
# Mandatory no
# Default:
# DBTLSCipher13=

####### For advanced users - TCP-related fine-tuning parameters #######

## Option: ListenBacklog
#       The maximum number of pending connections in the queue. This parameter is passed to
#       listen() function as argument 'backlog' (see "man listen").
#
# Mandatory: no
# Range: 0 - INT_MAX (depends on system, too large values may be silently truncated to implementation-specified maximum)
# Default: SOMAXCONN (hard-coded constant, depends on system)
# ListenBacklog=