ubuntu server 18.04 boot slow more 2 minute

After install ubuntu server 18.04 and found boot more 2 minute and have a error "a start job is running for wait for network to be configured"

How to fix this error check network interface
sudo networkctl
IDX LINK             TYPE               OPERATIONAL SETUP   
  1 lo               loopback           carrier     unmanaged
  2 enp4s5           ether              routable    configured
  3 enp5s0           ether              no-carrier  configuring

sudo networkctl status enp4s5

1. sudo vim /run/systemd/generator/network-online.target.wants/systemd-networkd-wait-online.service

change this line
ExecStart=/lib/systemd/systemd-networkd-wait-online
to
ExecStart=/lib/systemd/systemd-networkd-wait-online --interface=enp4s5 --quiet

------------------edit-----------------------------------

[Service]
Type=oneshot
ExecStart=/lib/systemd/systemd-networkd-wait-online --interface=enp4s5 --quiet
RemainAfterExit=yes
Ô

------------------end------------------------------------

2. reboot

Ref: a-start-job-is-running-for-wait-for-network-to-be-configured-ubuntu-server-17-1

install and configure x11vnc on ubuntu server 18.04 LTS

sudo apt-get install x11vnc

x11vnc -storepasswd 

Enter VNC password: *********
Verify password: *********  
Write password to /home/rahul/.vnc/passwd?  [y]/n y
Password written to: /home/rahul/.vnc/passwd

sudo x11vnc -auth guess -forever -loop -noxdamage -repeat -rfbauth /home/rahul/.vnc/passwd -rfbport 5900 -shared

script auto start

1. make file x11vnc.service in /etc/systemd/system :
sudo mcedit /etc/systemd/system/x11vnc.service (mcedit – my prefered editor , i’m sorry for vi :)))

with text (change RAHUL for you name):

[Unit]
Description=x11vnc remote desktop server
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/x11vnc -auth guess -forever -loop -noxdamage -repeat -rfbauth /home/RAHUL/.vnc/passwd -rfbport 5900 -shared

Restart=on-failure

[Install]
WantedBy=multi-user.target

2. sudo systemctl daemon-reload
sudo systemctl start x11vnc
sudo systemctl status x11vnc

3. if it’s worked
sudo systemctl enable x11vnc.service

Ref: setup-x11vnc-server-on-ubuntu-linuxmint

install and configure snmp

1. For CentOS 7
install service snmp

yum install net-snmp net-snmp-utils -y

Set configure file /etc/snmp/snmpd.conf
--------------------------------edit------------------------------------------------------------
#       sec.name  source          community
com2sec mynetwork  default       systemsecret

####
# Second, map the security name into a group name:

#       groupName      securityModel securityName
group   notConfigGroup v1           mynetwork
group   notConfigGroup v2c          mynetwork

# Make at least  snmpwalk -v 1 localhost -c public system fast again.

#       name           incl/excl     subtree         mask(optional)

view    systemview    included   .1.3.6.1.2.1.1

view    systemview    included   .1.3.6.1.2.1.25.1.1

####

# Finally, grant the group read-only access to the systemview view.

#       group          context sec.model sec.level prefix read   write  notif

access  notConfigGroup ""      any       noauth    exact  systemview none none

--------------------------------save configure-----------------------------------------------

Enable service

systemctl enable snmpd

systemctl start snmpd

systemctl status snmpd

Check port runing

netstat -tulpn

udp        0      0 0.0.0.0:161             0.0.0.0:*                           21402/snmpd

Test snmpd at local server

snmpwalk -v 1 -c systemsecret -O e 127.0.0.1

Add firewall

firewall-cmd --permanent --add-port=161/udp

firewall-cmd --reload

firewall-cmd --list-all

Ref: install-configure-snmp-rhel-7-centos-7

2. For Debain 9
Install service snmpd

apt install snmpd snmp libsnmp-dev

Edit configure /etc/snmp/snmpd.con
---------------------------------------------------------
#  AGENT BEHAVIOUR
#
#  Listen for connections from the local system only
agentAddress  udp:127.0.0.1:161,udp:192.168.0.xx:161

#  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

 rocommunity serversecret  default    -V systemonly

                                                 #  rocommunity6 is for IPv6

 rocommunity6 public  default   -V systemonly

#rocommunity secret  10.0.0.0/16

                                                 #  Full read-only access for SNMPv3

 rouser   authOnlyUser

#  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

                                                 # Application + End-to-End layers

sysServices    72

---------------------------------------------------------------------------

Enable service

systemctl enable snmpd

systemctl start snmpd

systemctl status snmpd

Check port runing

netstat -tulpn

udp        0      0 192.168.0.xx:161         0.0.0.0:*                           12142/snmpd         

udp        0      0 127.0.0.1:161           0.0.0.0:*                           12142/snmpd

ss -alnp | grep snmp | grep 161

udp    UNCONN     0      0      192.168.0.xx:161                   *:*                   users:(("snmpd",pid=12142,fd=12))

udp    UNCONN     0      0      127.0.0.1:161                   *:*                   users:(("snmpd",pid=12142,fd=9))

Test snmpd at local server

snmpwalk -v2c -c serversecret localhost

Add firewall

firewall-cmd --permanent --add-port=161/udp

firewall-cmd --reload

firewall-cmd --list-all

Ref: how-to-configure-snmp-version-2c-on-debian-9