snmpget : Unknown user name - ubuntu-16.04

Question

I am trying to install net-snmp from scratch to make snmpv3 to work on my computer.
I did install net-snmp and create the user, but when I want to make snmpget it reject me with snmpget: Unknown user name
To install net-snmp I followed the official guide
I did install the packages libperl-dev, snmp-mibs-downloader and snmp too using sudo apt-get install
Here is my /usr/local/share/snmp configuration where you can find the particular line rouser neutg
###############################################################################
#
# EXAMPLE.conf:
# An example configuration file for configuring the Net-SNMP agent ('snmpd')
# See the 'snmpd.conf(5)' man page for details
#
# Some entries are deliberately commented out, and will need to be explicitly activated
#
###############################################################################
#
# AGENT BEHAVIOUR
#
# Listen for connections from the local system only
# agentAddress udp:127.0.0.1:161
# Listen for connections on all interfaces (both IPv4 *and* IPv6)
agentAddress udp:161,udp6:[::1]:161
###############################################################################
#
# SNMPv3 AUTHENTICATION
#
# Note that these particular settings don't actually belong here.
# They should be copied to the file /var/lib/snmp/snmpd.conf
# and the passwords changed, before being uncommented in that file *only*.
# Then restart the agent
# createUser authOnlyUser MD5 "remember to change this password"
# createUser authPrivUser SHA "remember to change this one too" DES
# createUser internalUser MD5 "this is only ever used internally, but still change the password"
# If you also change the usernames (which might be sensible),
# then remember to update the other occurances in this example config file to match.
###############################################################################
#
# ACCESS CONTROL
#
# system + hrSystem groups only
view systemonly included .1.3.6.1.2.1.1
view systemonly included .1.3.6.1.2.1.25.1
# Full access from the local host
#rocommunity public localhost
# Default access to basic system info
rocommunity public default -V systemonly
# rocommunity6 is for IPv6
rocommunity6 public default -V systemonly
# Full access from an example network
# Adjust this network address to match your local
# settings, change the community string,
# and check the 'agentAddress' setting above
#rocommunity secret 10.0.0.0/16
# Full read-only access for SNMPv3
rouser authOnlyUser
# Full write access for encrypted requests
# Remember to activate the 'createUser' lines above
#rwuser authPrivUser priv
# It's no longer typically necessary to use the full 'com2sec/group/access' configuration
# r[ow]user and r[ow]community, together with suitable views, should cover most requirements
###############################################################################
#
# SYSTEM INFORMATION
#
# Note that setting these values here, results in the corresponding MIB objects being 'read-only'
# See snmpd.conf(5) for more details
sysLocation Sitting on the Dock of the Bay
sysContact Me <me#example.org>
# Application + End-to-End layers
sysServices 72
#
# Process Monitoring
#
# At least one 'mountd' process
proc mountd
# No more than 4 'ntalkd' processes - 0 is OK
proc ntalkd 4
# At least one 'sendmail' process, but no more than 10
proc sendmail 10 1
# Walk the UCD-SNMP-MIB::prTable to see the resulting output
# Note that this table will be empty if there are no "proc" entries in the snmpd.conf file
#
# Disk Monitoring
#
# 10MBs required on root disk, 5% free on /var, 10% free on all other disks
disk / 10000
disk /var 5%
includeAllDisks 10%
# Walk the UCD-SNMP-MIB::dskTable to see the resulting output
# Note that this table will be empty if there are no "disk" entries in the snmpd.conf file
#
# System Load
#
# Unacceptable 1-, 5-, and 15-minute load averages
load 12 10 5
# Walk the UCD-SNMP-MIB::laTable to see the resulting output
# Note that this table *will* be populated, even without a "load" entry in the snmpd.conf file
###############################################################################
#
# ACTIVE MONITORING
#
# send SNMPv1 traps
trapsink localhost public
# send SNMPv2c traps
#trap2sink localhost public
# send SNMPv2c INFORMs
#informsink localhost public
# Note that you typically only want *one* of these three lines
# Uncommenting two (or all three) will result in multiple copies of each notification.
#
# Event MIB - automatically generate alerts
#
# Remember to activate the 'createUser' lines above
iquerySecName internalUser
rouser internalUser
# generate traps on UCD error conditions
defaultMonitors yes
# generate traps on linkUp/Down
linkUpDownNotifications yes
###############################################################################
#
# EXTENDING THE AGENT
#
#
# Arbitrary extension commands
#
extend test1 /bin/echo Hello, world!
extend-sh test2 echo Hello, world! ; echo Hi there ; exit 35
#extend-sh test3 /bin/sh /tmp/shtest
# Note that this last entry requires the script '/tmp/shtest' to be created first,
# containing the same three shell commands, before the line is uncommented
# Walk the NET-SNMP-EXTEND-MIB tables (nsExtendConfigTable, nsExtendOutput1Table
# and nsExtendOutput2Table) to see the resulting output
# Note that the "extend" directive supercedes the previous "exec" and "sh" directives
# However, walking the UCD-SNMP-MIB::extTable should still returns the same output,
# as well as the fuller results in the above tables.
#
# "Pass-through" MIB extension command
#
#pass .1.3.6.1.4.1.8072.2.255 /bin/sh PREFIX/local/passtest
#pass .1.3.6.1.4.1.8072.2.255 /usr/bin/perl PREFIX/local/passtest.pl
# Note that this requires one of the two 'passtest' scripts to be installed first,
# before the appropriate line is uncommented.
# These scripts can be found in the 'local' directory of the source distribution,
# and are not installed automatically.
# Walk the NET-SNMP-PASS-MIB::netSnmpPassExamples subtree to see the resulting output
#
# AgentX Sub-agents
#
# Run as an AgentX master agent
master agentx
# Listen for network connections (from localhost)
# rather than the default named socket /var/agentx/master
#agentXSocket tcp:localhost:705
rouser neutg
Here is my persistant configuration file /var/net-snmp/snmpd.conf
createUser neutg SHA "password" AES passphrase
The command I run is :
snmpget -u neutg -A password -a SHA -X 'passphrase'
-x AES -l authPriv localhost -v 3 1.3.6.1.2.1.1
I don't understand why it do not take in count my user. (I did restart the snmpd after entering the user - multiple times!)
The version of net-snmp I use :
Thanks in advance :)

Answer 1

After many research I've found what the problem is.
snmpd was not taking in count my configuration files. I saw it using the command :
snmpd -Dread_config -H 2>&1 | grep "Reading" | sort -u
Which tells you which configurations files are loaded by snmpd.
You can see it as well looking at the configuration file /var/lib/snmp/snmpd.conf. When snmpd handle your users it creates special lines in the file. It looks like :
usmUser 1 3 0x80001f888074336938f74f7c5a00000000 "neutg" "neutg" NULL .1.3.6.1.6.3.10.1.1.3 0xf965e4ab0f35eebb3f0e3b30\
6bc0797c025821c5 .1.3.6.1.6.3.10.1.2.4 0xe277044beccd9991d70144c4c8f4b672 0x
usmUser 1 3 0x80001f888074336938f74f7c5a00000000 "myuser" "myuser" NULL .1.3.6.1.6.3.10.1.1.2 0x2223c2d00758353b7c3076\
236be02152 .1.3.6.1.6.3.10.1.2.2 0x2223c2d00758353b7c3076236be02152 0x
setserialno 1424757026
So if you do not see any usmUser it's probably that your badly added your users.
The soluce
sudo /usr/local/sbin/snmpd -c /var/net-snmp/snmpd.conf -c /usr/local/share/snmp/snmpd.conf