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<h1>rstory's NET-SNMP Developers Frequently Asked Questions Page</h1>
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<a href="FAQ.html">[Official FAQ]</a> |
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<a href="#tokens">[Debug tokens]</a> |
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<a href="#agentx">[AgentX]</a> |
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<a href="#install">[Install]</a> |
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<a href="#disable">[Disable]</a> |
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<a href="#errors">[Errors]</a> |
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<a href="#bits">[Bits]</a> |
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<a href="#embedded">[embedded perl]</a> |
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<a href="#smux">[SMUX]</a> |
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<a href="#entid">[Enterprise OID]</a> |
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<a href="#autodeps">[Automatic dependencies]</a> |
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<a href="#cross">[Cross compiling]</a> |
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<a href="#static">[Static linking]</a> |
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<a href="#readfds">[readfds]</a> |
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<a href="#sharing">[Sharing data]</a> |
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<a href="man1-mib2c.1.html">[mib2c.array-user.conf]</a> |
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<a href="#steps">[Baby Steps flow]</a> |
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This is just a quick page to answer some common questions that aren't covered
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in the <a href="/FAQ.html">official FAQ</a>.
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<a name="agentx"></a> <h2>AgentX</h2>
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<pre> To have the sub-agent communicate on a different socket, or with
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different permissions, add these line to your snmpd.conf
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agentxsocket /tmp/agentx
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# perms socket directory userid groupid
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agentxperms 777 777 rstory rstory
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and add this line to your subagent:
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netsnmp_ds_set_string(NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_X_SOCKET, "/tmp/agentx");
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*before* you call init_agent().
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<a name="install"></a><h2>install</h2>
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<pre> INSTALL_PREFIX goes before everything.. so, with the defaults, just
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setting INSTALL_PREFIX=/tmp would result in /tmp/usr/local..
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so INSTALL_PREFIX=/tmp prefix=/usr exec_prefix=/usr would go into /tmp/usr
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<a name="disable"></a><h2>disable</h2>
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<pre> If you are using net-snmp Version >= 5.1, then the following configure
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options may be useful to you:
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--disable-agent Do not build the agent (snmpd).
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--disable-applications Do not build the apps (snmpget, ...).
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--disable-manuals Do not install the manuals.
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--disable-scripts Do not install the scripts (mib2c, ...).
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--disable-mibs Do not install the mib files.
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--disable-mib-loading Do not include code that parses and
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manipulates the mib files.
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<a name="errors"></a><h2>errors</h2>
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noSuchName(2), -- for proxy compatibility
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badValue(3), -- for proxy compatibility
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readOnly(4), -- for proxy compatibility
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inconsistentValue(12),
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resourceUnavailable(13),
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authorizationError(16),
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<a name="bits"></a><h2>bits</h2>
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<pre> SNMPv1 use BIT STRINGs (RFC 1212, 5.1.1):
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(3) An object with BIT STRING syntax containing no more than
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32 bits becomes an INTEGER defined as a sum; otherwise if
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more than 32 bits are present, the object becomes an
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OCTET STRING, with the bits numbered from left-to-right,
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in which the least significant bits of the last octet may
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be "reserved for future use".
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SNMPv2 and beyond uses BITS (RFC 3417, 8.1):
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(3) When encoding an object whose syntax is described using the
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BITS construct, the value is encoded as an OCTET STRING, in
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which all the named bits in (the definition of) the bitstring,
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commencing with the first bit and proceeding to the last bit,
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are placed in bits 8 (high order bit) to 1 (low order bit) of
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the first octet, followed by bits 8 to 1 of each subsequent
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octet in turn, followed by as many bits as are needed of the
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final subsequent octet, commencing with bit 8. Remaining bits,
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if any, of the final octet are set to zero on generation and
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<a name="embedded"></a> <h2>embedded perl</h2>
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<pre> Add the following line to snmpd.conf:
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perl do "/path/to/perl_module.pl"
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1) Try staring up snmpd, like so: 'snmpd -Dperl'. Check your log files for:
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perl: initializing perl (/tmp/snmp_perl.pl)
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starting perl_module.pl
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perl_module.pl loaded ok
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registering at netSnmp.999
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perl: initializing perl (/usr/local/share/snmp/snmp_perl.pl)
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Can't open perl script "/usr/local/share/snmp/snmp_perl.pl": No such file or directory
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embedded perl support failed to initalize
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Then you need to locate snmp_perl.pl, and put it in the correct path, OR put
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the path in your snmpd.conf:
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perlInitFile /tmp/snmp_perl.pl
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2) Once it's loaded ok, try a walk:
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snmpwalk -v2c -c public localhost netSnmp.999
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You should see something like this in your logs:
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refs: NetSNMP::agent::netsnmp_mib_handler, NetSNMP::agent::reginfo, NetSNMP::agent::netsnmp_agent_request_info, NetSNMP::agent::netsnmp_request_infoPtr
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processing a request of type 161
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processing request of nsTransactionEntry.3
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.1.3.6.1.4.1.8072.999.1.2.1 -> hello world
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3) If not, maybe check /path/to/perl_module.pl and make sure it is executable.
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<a name="smux"></a> <h2>SMUX</h2>
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<pre> To turn off SMUX when you don't have the options of recompiling from source
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to disable SMUX support, you have to give it an invalid IP address to bind
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to. This may be OS specific. On Linux, if I put this in my snmpd.conf:
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I get an error at startup, and lsof or netstat show that snmpd is no longer
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listenting on port 199. If you get and error message about the smuxsocket
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token not being recongnized, then you're out of luck. You'll have to recompile
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from source (or just use local firewall rules to block connections to port
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<a name="entid"></a> <h2>Enterprise OID</h2>
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<pre> From: Dave Shield, RObert Story
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Recent Versions (5.x)
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---------------------
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If you want to *just* change the sysObjectID numbering,
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(and leave the notifications using the Net-SNMP enterprise OID)
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then use --with-enterprise-sysoid
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Or you could just use the snmpd.conf directive 'sysobjectid'
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to set this at run time.
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If you want to *just* change enterprise-specific notification OID
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(and leave the sysObjectID using the Net-SNMP values)
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then use --with-enterprise-notification-oid
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If you want to change *both* of these,
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then use --with-enterprise-oid
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Older Versions (4.2.x)
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----------------------
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In older version, you have to manuall update the version_id in
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agent/agent_trap.c:80
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oid version_id[] = { EXTENSIBLEMIB, AGENTID, OSTYPE };
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<a name="autodeps"></a> <h2>Automatic dependencies</h2>
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<pre> For auto-dependencies, add the following to your Makefile:
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@echo "Generating makefile $@ ..."
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@set -e; $(CC) -M $(COPTS) $(CFLAGS) $(CPPFLAGS) $< \
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| sed 's/\($*\)\.o[ :]*/\1.o $@ : /g' > $@; \
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[ -s $@ ] || $(RM) $(RMFLAGS) $@
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include $(SOURCES:.c=.d)
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<a name="cross"></a> <h2>Cross compiling</h2>
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<pre> From the net-snmp INSTALL file:
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Specifying the System Type
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==========================
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There may be some features `configure' can not figure out
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automatically, but needs to determine by the type of host the package
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will run on. Usually `configure' can figure that out, but if it prints
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a message saying it can not guess the host type, give it the
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`--host=TYPE' option. TYPE can either be a short name for the system
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type, such as `sun4', or a canonical name with three fields:
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See the file `config.sub' for the possible values of each field. If
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`config.sub' isn't included in this package, then this package doesn't
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need to know the host type.
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If you are building compiler tools for cross-compiling, you can also
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use the `--target=TYPE' option to select the type of system they will
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produce code for and the `--build=TYPE' option to select the type of
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system on which you are compiling the package.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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The most important configure options are:
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--with-cc=[cross-compiler]
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--with-ld=[cross-linker]
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--target=[target-environment]
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--with-endianness=[big|little]
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Other potentially useful options:
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Two simple examples of cross-compiling:
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./configure --target=ppc-linux --with-cc=ppc_405-gcc --with-endianness=big
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./configure --target=powerpc-snmc-linux-gnu --build=i386-redhat-linux \
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--with-endianness=big
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A more complex example involves setting environment variables for all
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the flags for the tools needed for the cross compile:
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export TOOLPATH=/opt/hardhat/devkit/ppc/405
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export PATH=$TOOLPATH/bin:$PATH
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export CFLAGS=' -g -fPIC -msoft-float -D_SOFT_FLOAT -Dlinux -mcpu=403'
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export CPPFLAGS='-I$TOOLPATH/include -I$TOOLPATH/target/usr/include'
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export ASFLAGS='-g -gstabs'
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export LDFLAGS='-Wl,-soname,-Bdynamic -lc'
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./configure --build=i686-pc-linux-gnu --host=powerpc \
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--target=powerpc-hardhat-linux-gnu --with-endianness=big
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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The mibgroup section is the most OS specific part of the agent. It's likely
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that you will have to remove some of them. You just need to figure out which
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For example, agent/mibgroup/mibII/tcpTable.c is a common module that doesn't
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work on new platforms. So if it isn't working, omit it during configure, like
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./configure --with-out-mib-modules=mibII/tcpTable
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Alternatively, you could work the other way. Start with a minimal
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./configure --enable-mini-agent
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and then start adding MIB modules one-by-one:
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./configure --enable-mini-agent
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--with-mib-modules=mibII/system_mib,mibII/sysORTable
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<a name="static"></a> <h2>Static linking</h2>
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<pre> mXaureliu: I want to compile the 5.1 snmptrapd binary with statically linked libraries.. Can anyone help me with this? Is it just a simple configure switch
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rstory: mXaureliu: you want static snmp libraries, or totally static (system libraries too)?
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mXaureliu: totally static.. everything in one executable
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mXaureliu: actually, how do i do both ways?
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rstory: for snmp libs, try 'configure --enable-shared=no'.. that won't build the shared libraries
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rstory: (though if you have previous versions of net-snmp libraries installed, the linker might pick those up and try and use them)
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rstory: for totally static, you'll have to tweak the Makefile
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rstory: add -Bstatic to LDFLAGS
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[note: actually, for totally static, 'configure --with-ldflags=-Bstatic']
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<a name="readfds"></a> <h2>readfds</h2>
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<pre> > can you please tell me the meaning of the third argument. obviously the
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> first parameter to register_readfd is a file descriptor and second is the
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The third parameter is arbitrary data that you can specify when you
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register the file descriptor, and will then be passed to the callback
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function when it's invoked.
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So if you were listening on two separate sockets, for very similar
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types of data, then you could use the same callback for both and
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use this third parameter to distinguish between them:
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fd1 = open( "/proc/tweedledum" );
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fd2 = open( "/proc/tweedledee" );
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register_readfd( fd1, who_broke_the_rattle(), "tweedledee" );
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register_readfd( fd2, who_broke_the_rattle(), "tweedledum" );
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who_broke_the_rattle( int fd, void *data )
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char *he_did = (char *)data;
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printf("%s broke the rattle!\n", he_did );
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<a name="sharing"></a> <h2>sharing data</h2>
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<pre> If two modules are compiled into the same agent/subagent, then just use a
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normal C global var. No need to involve net-snmp in the process.
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if they are different sub-agents, you are better off using tradition IPC
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mechanisms. there is no net-snmp api for sharing data between subagents.
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That said, *IF* you only need the data during processing of GET requests, or
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when you aren't processing a request at all, you send a snmp request to the
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master, which will query the other subagent. If you are processing a GET
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request and are compiled into the master, you will have to delegate the
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It's a little inefficient, compared to direct communication w/the other
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subagent and it *will not* work during set processing.
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<a name="tokens"></a> <h2>Debug Tokens</h2>
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<pre> Some of the more common ones are:
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Agent: agent, agentx, dlmod, handler, helper, snmpd, trap, table
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MIBs: init_mib, mib_init, parse-file, parse-mibs
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Add them to your snmp.conf like so:
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# optionally turn on time stamps
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debugTokens agentx/config
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If you put them in a different conf file, like snmpd.conf or myapp.conf,
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prefix each with '[snmp]', like so:
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This list was generated by running the following command in the main CVS branch:
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find . -name \"*.c\" -print | xargs grep DEBUGMSGT | grep \" | cut -f 2 -d\" | sort -u
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agentx/config/retries
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agentx/config/timeout
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check_getnext_results
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container_iterator:results
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container:null:find_next
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container:null:for_each
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container:null:get_null
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container:null:get_null_factory
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container:null:get_null_noalloc
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container:null:insert
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container:null:remove
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deinit_usm_post_config
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header_complex_add_data
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header_complex_extract_entry
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header_complex_generate_oid
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header_complex_generate_varoid
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header_complex_parse_oid
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helper:watcher:spinlock
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helper:watcher:timestamp
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host/hr_swrun::GetNextHR_SWRun
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initialize_table_ipCidrRouteTable
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initialize_table_mteEventNotificationTable
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initialize_table_mteEventTable
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initialize_table_netSnmpHostsTable
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initialize_table_nlmLogTable
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initialize_table_nlmLogVariableTable
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initialize_table_nsModuleTable
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initialize_table_nsTransactionTable
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lcd_get_enginetime_ex
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mibII/mta_sendmail.c:mta_sendmail_parse_config
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mibII/mta_sendmail.c:open_sendmailst
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mibII/mta_sendmail.c:read_sendmailcf
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mteEventTable:send_events
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mteTriggerBooleanTable
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mteTriggerExistenceTable
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mteTriggerTest:send_mte_trap
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mteTriggerThresholdTable
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netsnmp_agent_check_packet
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netsnmp_deregister_agent_nsap
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netsnmp_ds_handle_config
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netsnmp_ds_set_boolean
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netsnmp_ds_set_string
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netsnmp_ds_toggle_boolean
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netsnmp_instance_counter32_handler
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netsnmp_instance_int_handler
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netsnmp_instance_long_handler
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netsnmp_instance_ulong_handler
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netsnmp_register_agent_nsap
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netsnmp_register_mib_table_row
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netsnmp_table_data_set
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netsnmp_udp6_getSecName
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netsnmp_udp6_parse_security
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netsnmp_udp_getSecName
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netsnmp_udp_parse_security
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netsnmp_unix_getSecName
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netsnmp_unix_parse_security
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netsnmp_unix_transport
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read_config_copy_word
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read_config_read_data
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read_config_read_memory
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read_config_read_objid
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read_config_read_octet_string
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read_config_store_data_prefix
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read_config:traphandle
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snmp_clean_persistent
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snmpd_register_app_config_handler
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snmpNotifyFilterProfileTable
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snmpNotifyFilterTable
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snmp_pdu_realloc_rbuild
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snmpTargetParamsEntry
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ucd-snmp/pass_persist
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ucd-snmp/vmstat_aix4.c:update_stats
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ucd-snmp/vmstat_dynix.c:update_stats
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ucd-snmp/vmstat_hpux.c:update_stats
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ucd-snmp/vmstat_solaris2.c:update_stats
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<a name="steps"></a> <h2>Baby Steps Flow</h2>
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* Baby Steps Flow diagram (rev 2003.09.29.1330)
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* Legend: (test) [optional] <required>
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* ======== ============================================
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* (row exists?) N ->(row_creation) N >-->+
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* |<------------------+ |
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* RESERVE1 <object_syntax_checks> |
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* (err?) Y >------------------------>+
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* +++ (row existed?) N --->[row_creation] |
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* |<--------------N (err?) |
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* | [row_creation_cleanup]--->+
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* RESERVER2 [undo_setup] |
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* (err?) Y --->-------->--------->+ |
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* ACTION <set_values> | |
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* (err?) Y >---------+ \|/ |
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* +++ [consistency_checks] | | |
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* UNDO (err?) Y >-------[undo]-------->+ |
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* [reversible_commit] | |
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* (err?) Y >--[reverse_commit] | |
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* COMMIT <final_commit> | | |
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* (err?) Y >--[log msg] | |
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* | <-----------<+---<-----------+ |
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* FREE [undo_cleanup] |
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* |<--------------<-----------------+
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<!-- Created: Thu Jul 24 10:08:26 MET DST 1997 -->
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Last modified: Wed Mar 12 13:49:32 PST 2003
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