1SNMPD(8) Net-SNMP SNMPD(8)
2
6 snmpd - daemon to respond to SNMP request packets.
7
9 snmpd [OPTIONS] [LISTENING ADDRESSES]
10
12 snmpd is an SNMP agent which binds to a port and awaits requests from
13 SNMP management software. Upon receiving a request, it processes the
14 request(s), collects the requested information and/or performs the
15 requested operation(s) and returns the information to the sender.
16
18 -a Log the source addresses of incoming requests.
19 -A Append to the log file rather than truncating it.
21 -c FILE Read FILE as a configuration file (or a comma-separated list of
23 configuration files). Note that the loaded file will only
24 understand snmpd.conf tokens, unless the configuration type is
25 specified in the file as described in the snmp_config man page
26 under SWITCHING CONFIGURATION TYPES IN MID-FILE.
27 -C Do not read any configuration files except the ones optionally
29 specified by the -c option. Note that this behaviour also cov‐
30 ers the persistent configuration files. This may result in
31 dynamically-assigned values being reset following an agent
32 restart, unless the relevant persistent config files are
33 explicitly loaded using the -c option.
34 -d Dump (in hexadecimal) the sent and received SNMP packets.
36 -D[TOKEN[,...]]
38 Turn on debugging output for the given TOKEN(s). Without any
39 tokens specified, it defaults to printing all the tokens (which
40 is equivalent to the keyword "ALL"). You might want to try ALL
41 for extremely verbose output. Note: You can not put a space
42 between the -D flag and the listed TOKENs.
43 -f Do not fork() from the calling shell.
45 -g GID Change to the numerical group ID GID after opening listening
47 sockets.
48 -h, --help
50 Display a brief usage message and then exit.
51 -H Display a list of configuration file directives understood by
53 the agent and then exit.
54 -I [-]INITLIST
56 Specifies which modules should (or should not) be initialized
57 when the agent starts up. If the comma-separated INITLIST is
58 preceded with a '-', it is the list of modules that should not
59 be started. Otherwise this is the list of the only modules
60 that should be started.
61 To get a list of compiled modules, run the agent with the argu‐
63 ments -Dmib_init -H (assuming debugging support has been com‐
64 piled in).
65 -L[eEfFoOsSnN]
67 Specify where logging output should be directed (standard error
68 or output, to a file or via syslog). See LOGGING OPTIONS in
69 snmpcmd(1) for details.
70 -m MIBLIST
72 Specifies a colon separated list of MIB modules to load for
73 this application. This overrides the environment variable
74 MIBS. See snmpcmd(1) for details.
75 -M DIRLIST
77 Specifies a colon separated list of directories to search for
78 MIBs. This overrides the environment variable MIBDIRS. See
79 snmpcmd(1) for details.
80 -n NAME Set an alternative application name (which will affect the con‐
82 figuration files loaded). By default this will be snmpd,
83 regardless of the name of the actual binary.
84 -p FILE Save the process ID of the daemon in FILE.
86 -q Print simpler output for easier automated parsing.
88 -r Do not require root access to run the daemon. Specifically, do
90 not exit if files only accessible to root (such as /dev/kmem
91 etc.) cannot be opened.
92 -u UID Change to the user ID UID (which can be given in numerical or
94 textual form) after opening listening sockets.
95 -U Instructs the agent to not remove its pid file (see the -p
97 option) on shutdown. Overrides the leave_pidfile token in the
98 snmpd.conf file, see snmpd.conf(5).
99 -v, --version
101 Print version information for the agent and then exit.
102 -V Symbolically dump SNMP transactions.
104 -x ADDRESS
106 Listens for AgentX connections on the specified address rather
107 than the default "/var/agentx/master". The address can either
108 be a Unix domain socket path, or the address of a network
109 interface. The format is the same as the format of listening
110 addresses described below.
111 -X Run as an AgentX subagent rather than as an SNMP master agent.
113 --name="value"
115 Allows one to specify any token ("name") supported in the
116 snmpd.conf file and sets its value to "value". Overrides the
117 corresponding token in the snmpd.conf file. See snmpd.conf(5)
118 for the full list of tokens.
119
121 By default, snmpd listens for incoming SNMP requests on UDP port 161 on
122 all IPv4 interfaces. However, it is possible to modify this behaviour
123 by specifying one or more listening addresses as arguments to snmpd. A
124 listening address takes the form:
125 [<transport-specifier>:]<transport-address>
127 At its simplest, a listening address may consist only of a port number,
129 in which case snmpd listens on that UDP port on all IPv4 interfaces.
130 Otherwise, the <transport-address> part of the specification is parsed
131 according to the following table:
132 <transport-specifier> <transport-address> format
134 udp (default) hostname[:port] or IPv4-address[:port]
136 tcp hostname[:port] or IPv4-address[:port]
138 unix pathname
140 ipx [network]:node[/port]
142 aal5pvc or pvc [interface.][VPI.]VCI
144 udp6 or udpv6 or udpipv6 hostname[:port] or IPv6-address[:port]
146 tcp6 or tcpv6 or tcpipv6 hostname[:port] or IPv6-address[:port]
148 ssh hostname:port
150 dtlsudp hostname:port
152 Note that <transport-specifier> strings are case-insensitive so that,
154 for example, "tcp" and "TCP" are equivalent. Here are some examples,
155 along with their interpretation:
156 127.0.0.1:161 listen on UDP port 161, but only on the loop‐
158 back interface. This prevents snmpd being
159 queried remotely. The port specification
160 ":161" is not strictly necessary since that is
161 the default SNMP port.
162 TCP:1161 listen on TCP port 1161 on all IPv4 interfaces.
164 ipx:/40000 listen on IPX port 40000 on all IPX interfaces.
166 unix:/tmp/local-agent listen on the Unix domain socket
168 /tmp/local-agent.
169 /tmp/local-agent is identical to the previous specification,
171 since the Unix domain is assumed if the first
172 character of the <transport-address> is '/'.
173 PVC:161 listen on the AAL5 permanent virtual circuit
175 with VPI=0 and VCI=161 (decimal) on the first
176 ATM adapter in the machine.
177 udp6:10161 listen on port 10161 on all IPv6 interfaces.
179 ssh:127.0.0.1:22 Allows connections from the snmp subsystem on
181 the ssh server on port 22. The details of
182 using SNMP over SSH are defined below.
183 dtlsudp:127.0.0.1:9161 Listen for connections over DTLS on UDP port
185 9161. The snmp.conf file must have the
186 serverCert, configuration tokens defined.
187 Note that not all the transport domains listed above will always be
189 available; for instance, hosts with no IPv6 support will not be able to
190 use udp6 transport addresses, and attempts to do so will result in the
191 error "Error opening specified endpoint". Likewise, since AAL5 PVC
192 support is only currently available on Linux, it will fail with the
193 same error on other platforms.
194
196 ssh The SSH transport, on the server side, is actually just a unix
197 named pipe that can be connected to via a ssh subsystem config‐
198 ured in the main ssh server. The pipe location (configurable
199 with the sshtosnmpsocket token in snmp.conf) is
200 /var/net-snmp/sshtosnmp. Packets should be submitted to it via
201 the sshtosnmp application, which also sends the user ID as well
202 when starting the connection. The TSM security model should be
203 used when packets should process it.
204 The sshtosnmp command knows how to connect to this pipe and
206 talk to it. It should be configured in the OpenSSH sshd con‐
207 figuration file (which is normally /etc/ssh/sshd_config using
208 the following configuration line:
209 Subsystem snmp /usr/local/bin/sshtosnmp
212 The sshtosnmp command will need read/write access to the
214 /var/net-snmp/sshtosnmp pipe. Although it should be fairly
215 safe to grant access to the average user since it still
216 requires modifications to the ACM settings before the user can
217 perform operations, paranoid administrators may want to make
218 the /var/net-snmp directory accessible only by users in a par‐
219 ticular group. Use the sshtosnmpsocketperms snmp.conf config‐
220 ure option to set the permissions, owner and group of the cre‐
221 ated socket.
222 Access control can be granted to the user "foo" using the fol‐
224 lowing style of simple snmpd.conf settings:
225 rouser -s tsm foo authpriv
228 Note that "authpriv" is acceptable assuming as SSH protects
230 everything that way (assuming you have a non-insane setup).
231 snmpd has no notion of how SSH has actually protected a packet
232 and thus the snmp agent assumes all packets passed through the
233 SSH transport have been protected at the authpriv level.
234 dtlsudp The DTLS protocol, which is based off of TLS, requires both
236 client and server certificates to establish the connection and
237 authenticate both sides. In order to do this, the client will
238 need to configure the snmp.conf file with the clientCert con‐
239 figuration tokens. The server will need to configure the
240 snmp.conf file with the serverCert configuration tokens
241 defined.
242 Access control setup is similar to the ssh transport as the TSM
244 security model should be used to protect the packet.
245
247 snmpd checks for the existence of and parses the following files:
248 /etc/snmp/snmp.conf
250 Common configuration for the agent and applications. See
251 snmp.conf(5) for details.
252 /etc/snmp/snmpd.conf
254 /etc/snmp/snmpd.local.conf
256 Agent-specific configuration. See snmpd.conf(5) for details.
257 These files are optional and may be used to configure access con‐
258 trol, trap generation, subagent protocols and much else besides.
259 In addition to these two configuration files in /etc/snmp, the
261 agent will read any files with the names snmpd.conf and
262 snmpd.local.conf in a colon separated path specified in the SNMP‐
263 CONFPATH environment variable.
264 /usr/share/snmp/mibs/
266 The agent will also load all files in this directory as MIBs. It
267 will not, however, load any file that begins with a '.' or
268 descend into subdirectories.
269
271 (in recommended reading order)
272 snmp_config(5), snmp.conf(5), snmpd.conf(5)
274V5.8 30 Jun 2010 SNMPD(8)