SNMP_CONFIG(5) Net-SNMP SNMP_CONFIG(5)
NAME
snmp_config - handling of Net-SNMP configuration files
DESCRIPTION
The Net-SNMP package uses various configuration files to configure its
applications. This manual page merely describes the overall nature of
them, so that the other manual pages don't have to.
DIRECTORIES SEARCHED
First off, there are numerous places that configuration files can be
found and read from. By default, the applications look for configura-
tion files in the following 4 directories, in order: /etc/snmp,
/usr/share/snmp, /usr/lib/x86_64-linux-gnu/snmp, and $HOME/.snmp. In
each of these directories, it looks for files snmp.conf, snmpd.conf
and/or snmptrapd.conf, as well as snmp.local.conf, snmpd.local.conf
and/or snmptrapd.local.conf. *.local.conf are always read last. In this
manner, there are 8 default places a configuration file can exist for
any given configuration file type.
Additionally, the above default search path can be overridden by setting
the environment variable SNMPCONFPATH to a colon-separated list of di-
rectories to search for. The path for the persistent data should be in-
cluded when running applications that use persistent storage, such as
snmpd.
Applications will read persistent configuration files in the following
order of preference:
file in SNMP_PERSISTENT_FILE environment variable
directories in SNMPCONFPATH environment variable
directory defined by persistentDir snmp.conf variable
directory in SNMP_PERSISTENT_DIR environment variable
default /var/lib/snmp directory
Finally, applications will write persistent configuration files in the
following order of preference:
file in SNMP_PERSISTENT_FILE environment variable
directory defined by persistentDir snmp.conf variable
directory in SNMP_PERSISTENT_DIR environment variable
default /var/lib/snmp directory
Note: When using SNMP_PERSISTENT_FILE, the filename should match the
application name. For example, /var/net-snmp/snmpd.conf.
CONFIGURATION FILE TYPES
Each application may use multiple configuration files, which will con-
figure various different aspects of the application. For instance, the
SNMP agent (snmpd) knows how to understand configuration directives in
both the snmpd.conf and the snmp.conf files. In fact, most applications
understand how to read the contents of the snmp.conf files. Note, how-
ever, that configuration directives understood in one file may not be
understood in another file. For further information, read the associ-
ated manual page with each configuration file type. Also, most of the
applications support a -H switch on the command line that will list the
configuration files it will look for and the directives in each one that
it understands.
The snmp.conf configuration file is intended to be a application suite
wide configuration file that supports directives that are useful for
controlling the fundamental nature of all of the SNMP applications, such
as how they all manipulate and parse the textual SNMP MIB files.
SWITCHING CONFIGURATION TYPES IN MID-FILE
It's possible to switch in mid-file the configuration type that the
parser is supposed to be reading. Since that sentence doesn't make much
sense, lets give you an example: say that you wanted to turn on packet
dumping output for the agent by default, but you didn't want to do that
for the rest of the applications (ie, snmpget, snmpwalk, ...). Normally
to enable packet dumping in the configuration file you'd need to put a
line like:
dumpPacket true
into the snmp.conf file. But, this would turn it on for all of the ap-
plications. So, instead, you can put the same line in the snmpd.conf
file so that it only applies to the snmpd daemon. However, you need to
tell the parser to expect this line. You do this by putting a special
type specification token inside a [] set. In other words, inside your
snmpd.conf file you could put the above snmp.conf directive by adding a
line like so:
[snmp] dumpPacket true
This tells the parser to parse the above line as if it were inside a
snmp.conf file instead of an snmpd.conf file. If you want to parse a
bunch of lines rather than just one then you can make the context switch
apply to the remainder of the file or until the next context switch di-
rective by putting the special token on a line by itself:
# make this file handle snmp.conf tokens:
[snmp]
dumpPacket true
logTimestamp true
# return to our original snmpd.conf tokens:
[snmpd]
rocommunity mypublic
The same approach can be used to set configuration directives for a par-
ticular client application (or group of applications). For example, any
program that uses the 'snmp_parse_args()' call to handle command-line
arguments (including the standard command-line tools shipped as part of
the Net-SNMP distributions) will automatically read the config file 'sn-
mpapp.conf'. To set library-level settings for these applications (but
not other more-specific tools), use configuration such as the following:
[snmp] defCommunity myCommunity
for a single directive, or
# make this file handle snmp.conf tokens:
[snmp]
defCommunity myCommunity
defVersion 2c
# return to our original snmpapp.conf tokens:
[snmpapp]
for multiple settings. Similarly for any other application token (as
passed to init_snmp()).
COMMENTS
Any lines beginning with the character '#' in the configuration files
are treated as a comment and are not parsed.
INCLUDING OTHER CONFIGURATION FILES
It is possible to include other configuration files for processing dur-
ing normal configuration file processing.:
# include site specific config
includeFile site.conf
This will load the specified configuration file. The
path to file must be either absolute, starting with '/',
or relative. The relative path is then relative to the directory
where the parent file with 'includeFile' directive resides.
The included file name does not need to have '.conf' suffix.
# include a all *.conf files in a directory
includeDir /etc/snmp/config.d
This will search specified directory for all files with '.conf'
suffix and process them as if they were included using includeFile
directive. The configuration files are not processed in any particular
order.
The specified directory must be absolute directory path.
API INTERFACE
Information about writing C code that makes use of this system in either
the agent's MIB modules or in applications can be found in the net-
snmp_config_api(3) manual page.
SEE ALSO
snmpconf(1), netsnmp_config_api(3), snmp.conf(5), snmpd.conf(5)
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