Dts12: Latest FAQ revision - preparing for 5.5 release

2009-07-19T16:24:38Z

Latest FAQ revision - preparing for 5.5 release

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Although this is definitely a Frequently Asked Question on the project
mailing lists, it hasn't really been a Frequently ''Answered'' Question.
The basic problem is that none of the core development team have much
involvement or experience with embedded systems. And although we have
repeatedly put out a plea for implementation reports and advice, this
has not so far been particularly successful. So the first thing to say
is that the following suggestions should be treated with a greater than
usual level of suspicion.

The second thing to say is that compiling the Net-SNMP project for use
on an embedded system typically means compiling the '''agent''' (rather than
the trap receiver, or command-line tools). So that is what this entry
will concentrate on.

There are three main aspects to consider:
* how to compile the code,
* ''what'' code to compile, and
* how to install the resulting agent binary.

The Net-SNMP project uses the standard <CODE>configure</CODE> mechanism, so the
usual cross-compilation options are available - in particular <CODE>--host</CODE>
and <CODE>--target</CODE>. It is also possible to specify the compiler and linker
to use (<CODE>--with-cc</CODE> and <CODE>--with-ld</CODE>), and any special flags to pass
to them (<CODE>--with-cflags</CODE> and <CODE>--with-ldflags</CODE>). There shouldn't be
anything particularly special about compiling the Net-SNMP code, so
see the documentation for your target environment for more information.<br>
(And please let us know if there '''is''' anything special that should be
mentioned here!)

If the aim is simply to generate an SNMP agent to run on the target
system, it's probably not necessary to compile the command-line tools
or trap receiver. The configure option <CODE>--disable-applications</CODE> will
omit these elements. See the [[FAQ:Compiling_05|previous entry]] for other potentially
relevant useful options.

Unfortunately, the SNMP agent (and in particular, the code for individual
MIB modules) is the most system-specific part of the Net-SNMP software.
It may prove necessary to disable particular MIB modules if they do not
compile successfully, or attempt to use the wrong system-specific APIs.
This can be done using the configure option <CODE>--with-out-mib-modules</CODE>.
Alternatively, the option <CODE>--enable-mini-agent</CODE> will omit all but the
core MIB module code. Additional modules can then be added individually
using <CODE>--with-mib-modules</CODE>.

Further information about how to deal with problems with individual MIB
modules is reliant on suitable reports being forthcoming from the wider
Net-SNMP community. The ball is in your court!

Finally, installing the agent binary is '''not''' simply a matter of copying
the <CODE>snmpd</CODE> file onto the target system. The agent typically relies on
a number of additional libraries (and possibly the presence of assorted
MIB files, unless this has been explicitly omitted). It is normally
necessary to run <CODE>make install</CODE>, before copying the installed framework
to the target system.

If the install destination needs to be different to the eventual location
on the target system, this can be handled using the configure options
<CODE>--prefix</CODE> (for the target location) and <CODE>--with-install-prefix</CODE> (for the
temporary install location). Alternatively, this can be handled as part
of the install command:
make install prefix={target location} INSTALL_PREFIX={temp location}

Alternatively, if the agent is compiled with static linking (and no MIB
files), then it may be possible to simply copy the agent binary across to
the target system. See the [[FAQ:Compiling_07|next entry]] for details.

Template:FAQ:Compiling 06b - Revision history

Dts12: Latest FAQ revision - preparing for 5.5 release