[Ericsson AB]

5 Running the application

The chapter Running the application describes how the application is configured and started. The topics include:

Refer also to the chapter(s) Definition of Agent Configuration Files and Definition of Manager Configuration Files which contains more detailed information about the agent and manager configuration files.

5.1 Configuring the application

The following two directories must exist in the system to run the agent:

The following directory must exist in the system to run the manager:

The agent and manager uses (application) configuration parameters to find out where these directories are located. The parameters should be defined in an Erlang system configuration file. The following configuration parameters are defined for the SNMP application:

agent = [agent_opt()]
agent_opt() = {restart_type, restart_type()} | {agent_type, agent_type()} | {agent_verbosity, verbosity()} | {versions, versions()} | {priority, priority()} | {multi_threaded, multi_threaded()} | {db_dir, db_dir()} | {db_init_error, db_init_error()} | {local_db, local_db()} | {net_if, net_if()} | {mibs, mibs()} | {mib_storage, mib_storage()} | {mib_server, mib_server()} | {audit_trail_log, audit_trail_log()} | {error_report_mod, error_report_mod()} | {note_store, note_store()} | {symbolic_store, symbolic_store()} | {config, agent_config()}
The SNMP agent specific options.
manager = [manager_opt()]
manager_opt() = {restart_type, restart_type()} | {net_if, manager_net_if()} | {server, server()} | {note_store, note_store()} | {config, manager_config()} | {inform_request_behaviour, manager_irb()} | {mibs, manager_mibs()} | {priority, priority()} | {audit_trail_log, audit_trail_log()} | {versions, versions() | {def_user_module, def_user_module() | {def_user_data, def_user_data()}
The SNMP manager specific options.

Agent specific config options and types:

agent_type() = master | sub <optional>
If master, one master agent is started. Otherwise, no agents are started.
Default is master.
multi_threaded() = bool() <optional>
If true, the agent is multi-threaded, with one thread for each get request.
Default is false.
db_dir() = string() <mandatory>
Defines where the SNMP agent internal db files are stored.
local_db() = [local_db_opt()] <optional>
local_db_opt() = {repair, agent_repair()} | {auto_save, agent_auto_save()} | {verbosity, verbosity()}
Defines options specific for the SNMP agent local database.
For defaults see the options in local_db_opt().
agent_repair() = false | true | force <optional>
When starting snmpa_local_db it always tries to open an existing database. If false, and some errors occur, a new database is created instead. If true, an existing file will be repaired. If force, the table will be repaired even if it was properly closed.
Default is true.
agent_auto_save() = integer() | infinity <optional>
The auto save interval. The table is fluched to disk whenever not accessed for this amount of time.
Default is 5000.
agent_net_if() = [agent_net_if_opt()] <optional>
agent_net_if_opt() = {module, agent_net_if_module()} | {verbosity, verbosity()} | {options, agent_net_if_options()}
Defines options specific for the SNMP agent network interface entity.
For defaults see the options in agent_net_if_opt().
agent_net_if_module() = atom() <optional>
Module which handles the network interface part for the SNMP agent. Must implement the snmpa_network_interface behaviour.
Default is snmpa_net_if.
agent_net_if_options() = [agent_net_if_option()] <optional>
agent_net_if_option() = {bind_to, bind_to()} | {sndbuf, sndbuf()} | {recbuf, recbuf()} | {no_reuse, no_reuse()} | {req_limit, req_limit()}
These options are actually specific to the used module. The ones shown here are applicable to the default agent_net_if_module().
For defaults see the options in agent_net_if_option().
req_limit() = integer() | infinity <optional>
Max number of simultanious requests handled by the agent.
Default is infinity.
agent_mibs() = [string()] <optional>
Specifies a list of MIBs (including path) that defines which MIBs are initially loaded into the SNMP master agent.
Note that the following will allways be loaded:
Default is [].
mib_storage() = ets | {ets, Dir} | {ets, Dir, Action} | dets | {dets, Dir} | {dets, Dir, Action} | mnesia | {mnesia, Nodes} | {mnesia, Nodes, Action} <optional>
Specifies how info retrieved from the mibs will be stored.
If mib_storage is {ets, Dir}, the table will also be stored on file. If Dir is default, then db_dir will be used.
If mib_storage is dets or if Dir is default, then db_dir will be used for Dir.
If mib_storage is mnesia then erlang:nodes() will be used for Nodes.
Default is ets.
Dir = default | string(). Dir is the directory where the files will be stored. If default, then db_dir will be used.
Nodes = visible | connected | [node()]. Nodes = <c>visible is translated to erlang:nodes(visible). Nodes = <c>connected is translated to erlang:nodes(connected). If Nodes = [] then the own node is assumed.
Action = clear | keep. Default is keep. Action is used to specify what shall be done if the mnesia/dets table already exist.
mib_server() = [mib_server_opt()] <optional>
mib_server_opt() = {mibentry_override, mibentry_override()} | {trapentry_override, trapentry_override()} | {verbosity, verbosity()}
Defines options specific for the SNMP agent mib server.
For defaults see the options in mib_server_opt().
mibentry_override() = bool() <optional>
If this value is false, then when loading a mib each mib- entry is checked prior to installation of the mib. The perpose of the check is to prevent that the same symbolic mibentry name is used for different oid's.
Default is false.
trapentry_override() = bool() <optional>
If this value is false, then when loading a mib each trap is checked prior to installation of the mib. The perpose of the check is to prevent that the same symbolic trap name is used for different trap's.
Default is false.
error_report_mod() = atom() <optional>
Defines an error report module, implementing the snmpa_error_report behaviour. Two modules are provided with the toolkit: snmpa_error_logger and snmpa_error_io.
Default is snmpa_error_logger.
symbolic_store() = [symbolic_store_opt()]
symbolic_store_opt() = {verbosity, verbosity()}
Defines options specific for the SNMP agent symbolic store.
For defaults see the options in symbolic_store_opt().
agent_config() = [agent_config_opt()] <mandatory>
agent_config_opt() = {dir, agent_config_dir()} | {force_load, force_load()} | {verbosity, verbosity()}
Defines specific config related options for the SNMP agent.
For defaults see the options in agent_config_opt().
agent_config_dir = dir() <mandatory>
Defines where the SNMP agent configuration files are stored.
force_load() = bool() <optional>
If true the configuration files are re-read during startup, and the contents of the configuration database ignored. Thus, if true, changes to the configuration database are lost upon reboot of the agent.
Default is false.

Manager specific config options and types:

server() = [server_opt()] <optional>
server_opt() = {timeout, server_timeout()} | {verbosity, verbosity()}
Specifies the options for the manager server process.
Default is silence.
server_timeout() = integer() <optional>
Asynchroneous request cleanup time. For every requests, some info is stored internally, in order to be able to deliver the reply (when it arrives) to the proper destination. If the reply arrives, this info will be deleted. But if there is no relpy (in time), the info has to be deleted after the best before time has been passed. This cleanup will be performed at regular intervals, defined by the server_timeout() time. The information will have a best before time, defined by the Expire time given when calling the request function (see ag, agn and as).
Time in milli-seconds.
Default is 30000.
manager_config() = [manager_config_opt()] <mandatory>
manager_config_opt() = {dir, manager_config_dir()} | {db_dir, manager_db_dir()} | {db_init_error, db_init_error()} | {repair, manager_repair()} | {auto_save, manager_auto_save()} | {verbosity, verbosity()}
Defines specific config related options for the SNMP manager.
For defaults see the options in manager_config_opt().
manager_config_dir = dir() <mandatory>
Defines where the SNMP manager configuration files are stored.
manager_db_dir = dir() <mandatory>
Defines where the SNMP manager store persistent data.
manager_repair() = false | true | force <optional>
Defines the repair option for the persistent database (if and how the table is repaired when opened).
Default is true.
manager_auto_save() = integer() | infinity <optional>
The auto save interval. The table is fluched to disk whenever not accessed for this amount of time.
Default is 5000.
manager_irb() = auto | user | {user, integer()} <optional>
This option defines how the manager will handle the sending of response (acknowledgement) to received inform-requests.
See snmpm_network_interface , handle_inform and definition of the manager net if for more info.
Default is auto.
manager_mibs() = [string()] <optional>
Specifies a list of MIBs (including path) and defines which MIBs are initially loaded into the SNMP manager.
Default is [].
manager_net_if() = [manager_net_if_opt()] <optional>
manager_net_if_opt() = {module, manager_net_if_module()} | {verbosity, verbosity()} | {options, manager_net_if_options()}
Defines options specific for the SNMP manager network interface entity.
For defaults see the options in manager_net_if_opt().
manager_net_if_options() = [manager_net_if_option()] <optional>
manager_net_if_option() = {bind_to, bind_to()} | {sndbuf, sndbuf()} | {recbuf, recbuf()} | {no_reuse, no_reuse()}
These options are actually specific to the used module. The ones shown here are applicable to the default manager_net_if_module().
For defaults see the options in manager_net_if_option().
manager_net_if_module() = atom() <optional>
Module which handles the network interface part for the SNMP manager. Must implement the snmpm_network_interface behaviour.
Default is snmpm_net_if.
def_user_module() = atom() <optional>
The module implementing the default user. See the snmpm_user behaviour.
Default is snmpm_user_default.
def_user_data() = term() <optional>
Data for the default user. Passed to the user when calling the callback functions.
Default is undefined.

Common config types:

restart_type() = permanent | transient | temporary
See supervisor documentaion for more info.
Default is permanent for the agent and transient for the manager.
db_init_error() = terminate | create
Defines what to do if the agent is unable to open an existing database file. terminate means that the agent/manager will terminate and create means that the agent/manager will remove the faulty file(s) and create new ones.
Default is terminate.
priority() = atom() <optional>
Defines the Erlang priority for all SNMP processes.
Default is normal.
versions() = [version()] <optional>
version() = v1 | v2 | v3
Which SNMP versions shall be accepted/used.
Default is [v1,v2,v3].
verbosity() = silence | info | log | debug | trace <optional>
Verbosity for a SNMP process. This specifies now much debug info is printed.
Default is silence.
bind_to() = bool() <optional>
If true, net_if binds to the IP adress. If false, net_if listens on any IP address on the host where it is running.
Default is false.
no_reuse() = bool() <optional>
If true, net_if does not specify that the IP and port address should be reusable. If false, the address is set to reusable.
Default is false.
recbuf() = integer() <optional>
Receive buffer size.
Default value is defined by gen_udp.
sndbuf() = integer() <optional>
Send buffer size.
Default value is defined by gen_udp.
note_store() = [note_store_opt()] <optional>
note_store_opt() = {timeout, note_store_timeout()} | {verbosity, verbosity()}
Specifies the options for the SNMP note store.
For defaults see the options in note_store_opt().
note_store_timeout() = integer() <optional>
Note cleanup time. When storing a note in the note store, each note is given lifetime. Every timeout the note_store process performs a GC to remove the expired note's. Time in milli-seconds.
Default is 30000.
audit_trail_log() [audit_trail_log_opt()] <optional>
audit_trail_log_opt() = {type, atl_type()} | {dir, atl_dir()} | {size, atl_size()} | {repair, atl_repair()}
If present, this option specifies the options for the audit trail logging. The disk_log module is used to maintain a wrap log. If present, the dir and size options are mandatory.
If not present, audit trail logging is not used.
atl_type() = read | write | read_write <optional>
Specifies what type of an audit trail log should be used. The effect of the type is actually different for the the agent and the manager.
For the agent:
For the manager:
Default is read_write.
atl_dir = dir() <mandatory>
Specifies where the audit trail log should be stored.
If audit_trail_log specifies that logging should take place, this parameter must be defined.
atl_size() = {integer(), integer()} <mandatory>
Specifies the size of the audit trail log. This parameter is sent to disk_log.
If audit_trail_log specifies that logging should take place, this parameter must be defined.
atl_repair() = true | false | truncate | snmp_repair <optional>
Specifies if and how the audit trail log shall be repaired when opened. Unless this parameter has the value snmp_repair it is sent to disk_log. If, on the other hand, the value is snmp_repair, snmp attempts to handle certain faults on it's own. And even if it cannot repair the file, it does not truncate it directly, but instead moves it aside for later off-line analysis.
Default is true.

5.2 Modifying the Configuration Files

To to start the application (agent and/or manager), the configuration files must be modified and there are two ways of doing this. Either edit the files manually, or run the configuration tool as follows.

If authentication or encryption is used (SNMPv3 only), start the crypto application. 

1> snmp:config().

Simple SNMP configuration tool (version 4.0)
------------------------------------------------
Note: Non-trivial configurations still has to be
      done manually. IP addresses may be entered 
      as dront.ericsson.se (UNIX only) or
      123.12.13.23
------------------------------------------------

Configure an agent (y/n)? [y] 

Agent system config: 
--------------------
1. Agent process priority (low/normal/high) [normal] 
2. What SNMP version(s) should be used (1,2,3,1&2,1&2&3,2&3)? [3] 1&2&3
3. Configuration directory (absolute path)? [/ldisk/snmp] /ldisk/snmp/agent/conf
4. Config verbosity (silence/info/log/debug/trace)? [silence] 
5. Database directory (absolute path)? [/ldisk/snmp] /ldisk/snmp/agent/db
6. Mib storage type (ets/dets/mnesia)? [ets] 
7. Symbolic store verbosity (silence/info/log/debug/trace)? [silence] 
8. Local DB verbosity (silence/info/log/debug/trace)? [silence] 
9. Local DB repair (true/false/force)? [true] 
10. Local DB auto save (infinity/milli seconds)? [5000] 
11. Error report module? [snmpa_error_logger] 
12. Agent type (master/sub)? [master] 
13. Master-agent verbosity (silence/info/log/debug/trace)? [silence] log
14. Shall the agent re-read the configuration files during startup 
    (and ignore the configuration database) (true/false)? [true] 
15. Multi threaded agent (true/false)? [false] true
16. Check for duplicate mib entries when installing a mib (true/false)? [false] 
17. Check for duplicate trap names when installing a mib (true/false)? [false] 
18. Mib server verbosity (silence/info/log/debug/trace)? [silence] 
19. Note store verbosity (silence/info/log/debug/trace)? [silence] 
20. Note store GC timeout? [30000] 
21. Shall the agent use an audit trail log (y/n)? [n] y
21b. Audit trail log type (write/read_write)? [read_write] 
21c. Where to store the audit trail log? [/ldisk/snmp] /ldisk/snmp/agent/log
21d. Max number of files? [10] 
21e. Max size (in bytes) of each file? [10240] 
21f. Audit trail log repair (true/false/truncate)? [true] 
22. Which network interface module shall be used? [snmpa_net_if] 
23. Network interface verbosity (silence/info/log/debug/trace)? [silence] log
24. Bind the agent IP address (true/false)? [false] 
25. Shall the agents IP address and port be not reusable (true/false)? [false] 
26. Agent request limit (used for flow control) (infinity/pos integer)? [infinity] 32
27. Receive buffer size of the agent (in bytes) (default/pos integer)? [default] 

Agent snmp config: 
------------------
1. System name (sysName standard variable) [bmk's agent] 
2. Engine ID (snmpEngineID standard variable) [bmk's engine] 
3. Max message size? [484] 
4. The UDP port the agent listens to. (standard 161) [4000] 
5. IP address for the agent (only used as id 
   when sending traps) [127.0.0.1] 
6. IP address for the manager (only this manager 
   will have access to the agent, traps are sent 
   to this one) [127.0.0.1] 
7. To what UDP port at the manager should traps 
   be sent (standard 162)? [5000] 
8. Do you want a none- minimum- or semi-secure configuration? 
   Note that if you chose v1 or v2, you won't get any security for these
   requests (none, minimum, semi_des, semi_aes) [minimum] 
making sure crypto server is started...
8b. Give a password of at least length 8. It is used to generate 
    private keys for the configuration:  kalle-anka
9. Current configuration files will now be overwritten. Ok (y/n)? [y] 

- - - - - - - - - - - - -
Info: 1. SecurityName "initial" has noAuthNoPriv read access
         and authenticated write access to the "restricted"
         subtree.
      2. SecurityName "all-rights" has noAuthNoPriv read/write
         access to the "internet" subtree.
      3. Standard traps are sent to the manager.
      4. Community "public" is mapped to security name "initial".
      5. Community "all-rights" is mapped to security name "all-rights".
The following agent files were written: agent.conf, community.conf,
standard.conf, target_addr.conf, target_params.conf, 
notify.conf, vacm.conf and usm.conf
- - - - - - - - - - - - -

Configure a manager (y/n)? [y] 

Manager system config: 
----------------------
1. Manager process priority (low/normal/high) [normal] 
2. What SNMP version(s) should be used (1,2,3,1&2,1&2&3,2&3)? [3] 1&2&3
3. Configuration directory (absolute path)? [/ldisk/snmp] /ldisk/snmp/manager/conf
4. Config verbosity (silence/info/log/debug/trace)? [silence] log
5. Database directory (absolute path)? [/ldisk/snmp] /ldisk/snmp/manager/db
6. Database repair (true/false/force)? [true] 
7. Database auto save (infinity/milli seconds)? [5000] 
8. Server verbosity (silence/info/log/debug/trace)? [silence] log
9. Server GC timeout? [30000] 
10. Note store verbosity (silence/info/log/debug/trace)? [silence] 
11. Note store GC timeout? [30000] 
12. Which network interface module shall be used? [snmpm_net_if] 
13. Network interface verbosity (silence/info/log/debug/trace)? [silence] log
14. Bind the manager IP address (true/false)? [false] 
15. Shall the manager IP address and port be not reusable (true/false)? [false] 
16. Receive buffer size of the manager (in bytes) (default/pos integer)? [default] 
17. Shall the manager use an audit trail log (y/n)? [n] y
17b. Where to store the audit trail log? [/ldisk/snmp] /ldisk/snmp/manager/log
17c. Max number of files? [10] 
17d. Max size (in bytes) of each file? [10240] 
17e. Audit trail log repair (true/false/truncate)? [true] 
18. Do you wish to assign a default user [yes] or use
    the default settings [no] (y/n)? [n] 

Manager snmp config: 
--------------------
1. Engine ID (snmpEngineID standard variable) [bmk's engine] 
2. Max message size? [484] 
3. IP address for the manager (only used as id 
   when sending requests) [127.0.0.1] 
4. Port number (standard 162)? [5000] 
5. Configure a user of this manager (y/n)? [y] 
5b. User id? kalle
5c. User callback module? snmpm_user_default
5d. User (callback) data? [undefined] 
5. Configure a user of this manager (y/n)? [y] n
6. Configure an agent handled by this manager (y/n)? [y] 
6b. User id? kalle
6c. Target name? [bmk's agent] 
6d. Version (1/2/3)? [1] 3
6e. Community string ? [public] 
6f. Engine ID (snmpEngineID standard variable) [bmk's engine] 
6g. IP address for the agent [127.0.0.1] 
6h. The UDP port the agent listens to. (standard 161) [4000] 
6i. Retransmission timeout (infinity/pos integer)? [infinity] 
6j. Max message size? [484] 
6k. Security model (any/v1/v2c/usm)? [any] usm
6l. Security name? ["initial"] 
6m. Security level (noAuthNoPriv/authNoPriv/authPriv)? [noAuthNoPriv] authPriv
6. Configure an agent handled by this manager (y/n)? [y] n
7. Configure an usm user handled by this manager (y/n)? [y] 
7a. Engine ID [bmk's engine] 
7b. User name? hobbes
7c. Security name? [hobbes] 
7d. Authentication protocol (no/sha/md5)? [no] sha
7e  Authentication [sha] key (length 0 or 20)? [""] [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
7d. Priv protocol (no/des/aes)? [no] des
7f  Priv [des] key (length 0 or 16)? [""] 10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25
7. Configure an usm user handled by this manager (y/n)? [y] n
8. Current configuration files will now be overwritten. Ok (y/n)? [y] 

- - - - - - - - - - - - -
The following manager files were written: manager.conf, agents.conf , users.conf and usm.conf
- - - - - - - - - - - - -

--------------------
Configuration directory for system file (absolute path)? [/ldisk/snmp] 
ok

5.3 Starting the application

Start Erlang with the command: 

erl -config /tmp/snmp/sys

If authentication or encryption is used (SNMPv3 only), start the crypto application. If this step is forgotten, the agent will not start, but report a {config_error,{unsupported_crypto,_}} error. 

1> application:start(crypto).
ok
    

2> application:start(snmp).
ok

5.4 Debugging the application

It is possible to debug every (non-supervisor) process of the application (both agent and manager), possibly with the exception of the net_if module(s), which could be supplied by a user of the application). This is done by calling the snmpa:verbosity/2 and snmpm:verbosity/2 function(s) and/or using configuration parameters. The verbosity itself has several levels: silence | info | log | debug | trace. For the lowest verbosity silence, nothing is printed. The higher the verbosity, the more is printed. Default value is always silence. 

3> snmpa:verbosity(master_agent, log).
ok
5> snmpa:verbosity(net_if, log).
ok
6> 
%% Example of output from the agent when a get-next-request arrives:
** SNMP NET-IF LOG: 
   got paket from {147,12,12,12}:5000

** SNMP NET-IF MPD LOG: 
   v1, community: all-rights

** SNMP NET-IF LOG: 
   got pdu from {147,12,12,12}:5000 {pdu, 'get-next-request',
                                          62612569,noError,0,
                                          [{varbind,[1,1],'NULL','NULL',1}]}

** SNMP MASTER-AGENT LOG: 
   apply: snmp_generic,variable_func,[get,{sysDescr,persistent}]

** SNMP MASTER-AGENT LOG: 
   returned: {value,"Erlang SNMP agent"}

** SNMP NET-IF LOG: 
   reply pdu: {pdu,'get-response',62612569,noError,0,
                   [{varbind,[1,3,6,1,2,1,1,1,0],
                             'OCTET STRING',
                             "Erlang SNMP agent",1}]}

** SNMP NET-IF INFO: time in agent: 19711 mysec

Another useful function for debugging is snmpa_local_db:print/0,1,2. For example, this function can show the counters snmpInPkts and snmpOutPkts. Enter the following command: 

4> snmpa_local_db:print().
%% A lot of information.
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