Ubuntu Manpage: snmpd - daemon to respond to SNMP request packets.

Provided by: snmpd_5.7.3+dfsg-1.8ubuntu3.8_amd64

NAME

       snmpd - daemon to respond to SNMP request packets.

SYNOPSIS

       snmpd [OPTIONS] [LISTENING ADDRESSES]

DESCRIPTION

       snmpd  is  an  SNMP  agent which binds to a port and awaits requests from SNMP management software.  Upon
       receiving a request, it processes the request(s), collects the requested information and/or performs  the
       requested operation(s) and returns the information to the sender.

OPTIONS

-a Log the source addresses of incoming requests.

-A Append to the log file rather than truncating it.

-c FILE Read FILE as a configuration file (or a comma-separated list of configuration files). Note that
the loaded file will only understand snmpd.conf tokens, unless the configuration type is
specified in the file as described in the snmp_config man page under SWITCHING CONFIGURATION
TYPES IN MID-FILE.

-C Do not read any configuration files except the ones optionally specified by the -c option. Note
that this behaviour also covers the persistent configuration files. This may result in
dynamically-assigned values being reset following an agent restart, unless the relevant
persistent config files are explicitly loaded using the -c option.

-d Dump (in hexadecimal) the sent and received SNMP packets.

-D[TOKEN[,...]]
Turn on debugging output for the given TOKEN(s). Without any tokens specified, it defaults to
printing all the tokens (which is equivalent to the keyword "ALL"). You might want to try ALL
for extremely verbose output. Note: You can not put a space between the -D flag and the listed
TOKENs.

-f Do not fork() from the calling shell.

-g GID Change to the numerical group ID GID after opening listening sockets.

-h, --help
Display a brief usage message and then exit.

-H Display a list of configuration file directives understood by the agent and then exit.

-I [-]INITLIST
Specifies which modules should (or should not) be initialized when the agent starts up. If the
comma-separated INITLIST is preceded with a '-', it is the list of modules that should not be
started. Otherwise this is the list of the only modules that should be started.

To get a list of compiled modules, run the agent with the arguments -Dmib_init -H (assuming
debugging support has been compiled in).

-L[eEfFoOsS]
Specify where logging output should be directed (standard error or output, to a file or via
syslog). See LOGGING OPTIONS in snmpcmd(1) for details.

-m MIBLIST
Specifies a colon separated list of MIB modules to load for this application. This overrides the
environment variable MIBS. See snmpcmd(1) for details.

-M DIRLIST
Specifies a colon separated list of directories to search for MIBs. This overrides the
environment variable MIBDIRS. See snmpcmd(1) for details.

-n NAME Set an alternative application name (which will affect the configuration files loaded). By
default this will be snmpd, regardless of the name of the actual binary.

-p FILE Save the process ID of the daemon in FILE.

-q Print simpler output for easier automated parsing.

-r Do not require root access to run the daemon. Specifically, do not exit if files only accessible
to root (such as /dev/kmem etc.) cannot be opened.

-u UID Change to the user ID UID (which can be given in numerical or textual form) after opening
listening sockets.

-U Instructs the agent to not remove its pid file (see the -p option) on shutdown. Overrides the
leave_pidfile token in the snmpd.conf file, see snmpd.conf(5).

-v, --version
Print version information for the agent and then exit.

-V Symbolically dump SNMP transactions.

-x ADDRESS
Listens for AgentX connections on the specified address rather than the default
"/var/agentx/master". The address can either be a Unix domain socket path, or the address of a
network interface. The format is the same as the format of listening addresses described below.

-X Run as an AgentX subagent rather than as an SNMP master agent.

--name="value"
Allows one to specify any token ("name") supported in the snmpd.conf file and sets its value to
"value". Overrides the corresponding token in the snmpd.conf file. See snmpd.conf(5) for the full
list of tokens.

LISTENING ADDRESSES

By default, snmpd listens for incoming SNMP requests on UDP port 161 on all IPv4 interfaces. However, it
is possible to modify this behaviour by specifying one or more listening addresses as arguments to snmpd.
A listening address takes the form:

[<transport-specifier>:]<transport-address>

At its simplest, a listening address may consist only of a port number, in which case snmpd listens on
that UDP port on all IPv4 interfaces. Otherwise, the <transport-address> part of the specification is
parsed according to the following table:

<transport-specifier> <transport-address> format

udp (default) hostname[:port] or IPv4-address[:port]

tcp hostname[:port] or IPv4-address[:port]

unix pathname

ipx [network]:node[/port]

aal5pvc or pvc [interface.][VPI.]VCI

udp6 or udpv6 or udpipv6 hostname[:port] or IPv6-address[:port]

tcp6 or tcpv6 or tcpipv6 hostname[:port] or IPv6-address[:port]

ssh hostname:port

dtlsudp hostname:port

Note that <transport-specifier> strings are case-insensitive so that, for example, "tcp" and "TCP" are
equivalent. Here are some examples, along with their interpretation:

127.0.0.1:161 listen on UDP port 161, but only on the loopback interface. This prevents snmpd
being queried remotely. The port specification ":161" is not strictly necessary
since that is the default SNMP port.

TCP:1161 listen on TCP port 1161 on all IPv4 interfaces.

ipx:/40000 listen on IPX port 40000 on all IPX interfaces.

unix:/tmp/local-agent listen on the Unix domain socket /tmp/local-agent.

/tmp/local-agent is identical to the previous specification, since the Unix domain is assumed if
the first character of the <transport-address> is '/'.

PVC:161 listen on the AAL5 permanent virtual circuit with VPI=0 and VCI=161 (decimal) on
the first ATM adapter in the machine.

udp6:10161 listen on port 10161 on all IPv6 interfaces.

ssh:127.0.0.1:22 Allows connections from the snmp subsystem on the ssh server on port 22. The
details of using SNMP over SSH are defined below.

dtlsudp:127.0.0.1:9161 Listen for connections over DTLS on UDP port 9161. The snmp.conf file must have
the serverCert, configuration tokens defined.

Note that not all the transport domains listed above will always be available; for instance, hosts with
no IPv6 support will not be able to use udp6 transport addresses, and attempts to do so will result in
the error "Error opening specified endpoint". Likewise, since AAL5 PVC support is only currently
available on Linux, it will fail with the same error on other platforms.

Transport Specific Notes

ssh The SSH transport, on the server side, is actually just a unix named pipe that can be connected
to via a ssh subsystem configured in the main ssh server. The pipe location (configurable with
the sshtosnmpsocket token in snmp.conf) is /var/net-snmp/sshtosnmp. Packets should be submitted
to it via the sshtosnmp application, which also sends the user ID as well when starting the
connection. The TSM security model should be used when packets should process it.

The sshtosnmp command knows how to connect to this pipe and talk to it. It should be configured
in the OpenSSH sshd configuration file (which is normally /etc/ssh/sshd_config using the
following configuration line:

Subsystem snmp /usr/local/bin/sshtosnmp

The sshtosnmp command will need read/write access to the /var/net-snmp/sshtosnmp pipe. Although
it should be fairly safe to grant access to the average user since it still requires
modifications to the ACM settings before the user can perform operations, paranoid administrators
may want to make the /var/net-snmp directory accessible only by users in a particular group. Use
the sshtosnmpsocketperms snmp.conf configure option to set the permissions, owner and group of
the created socket.

Access control can be granted to the user "foo" using the following style of simple snmpd.conf
settings:

rouser -s tsm foo authpriv

Note that "authpriv" is acceptable assuming as SSH protects everything that way (assuming you
have a non-insane setup). snmpd has no notion of how SSH has actually protected a packet and
thus the snmp agent assumes all packets passed through the SSH transport have been protected at
the authpriv level.

dtlsudp The DTLS protocol, which is based off of TLS, requires both client and server certificates to
establish the connection and authenticate both sides. In order to do this, the client will need
to configure the snmp.conf file with the clientCert configuration tokens. The server will need
to configure the snmp.conf file with the serverCert configuration tokens defined.

Access control setup is similar to the ssh transport as the TSM security model should be used to
protect the packet.

CONFIGURATION FILES

       snmpd checks for the existence of and parses the following files:

       /etc/snmp/snmp.conf
             Common configuration for the agent and applications. See snmp.conf(5) for details.

       /etc/snmp/snmpd.conf

       /etc/snmp/snmpd.local.conf
             Agent-specific  configuration.  See snmpd.conf(5) for details.  These files are optional and may be
             used to configure access control, trap generation, subagent protocols and much else besides.

             In addition to these two configuration files in /etc/snmp, the agent will read any files  with  the
             names  snmpd.conf  and  snmpd.local.conf  in  a  colon separated path specified in the SNMPCONFPATH
             environment variable.

       /usr/share/snmp/mibs/
             The agent will also load all files in this directory as MIBs.  It will not, however, load any  file
             that begins with a '.' or descend into subdirectories.