Access file windows from Linux

Linux server
List share file on windows
smbclient --user=windows user -L //IP Address windows server
smbclient --user=U001 -L //172.16.0.xx

Access file on windows server
smbclient //IP Address windows server/File share -U windows user
smbclient //172.16.0.xx/Fileshare -U U0001

install epel-release on centos 8

install epel-release

Turn on EPEL repo on CentOS 8

Make sure EPEL repo enabled and installed. If not, run:
vivek@centos8-box:$ sudo yum -y install epel-release
vivek@centos8-box:$ sudo yum repolist

Ref: how-to-install-htop-on-centos-linux-8

Linux command check IP public when you connect to internet at that location

1. dig +short myip.opendns.com @resolver1.opendns.com
2. dig TXT +short o-o.myaddr.l.google.com @ns1.google.com | awk -F'"' '{ print $2}'

Ref: debian 10 set up openvpn-server in 5 minutes

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

Configure Master / Slave BIND DNS Server on CentOS 8 / RHEL 8

Configure Master / Slave BIND DNS Server on CentOS 8 / RHEL 8

install-bind-private-dns-server-on-rhel-8

for check zone file

named-checkzone abc.com /var/named/abc.com.zone

Directory zone = /var/named/

dnstop ens192
dnstop -l 2 ens192
dnstop -l 3 ens192
yum install dnstop

How to Add New Disks Using LVM to an Existing Linux System

Read on this web site add-new-disks-using-lvm-to-linux

how to change screen login ubuntu 18.04 budgie

1. create file slick-greeter.conf on /etc/lightdm/

sudo vim /etc/lightdm/slick-greeter.conf
------------------------------------------------------
[Greeter]
#background=/usr/share/backgrounds/Definitive_Light_Zen_Orange_by_Pierre_Cante.jpg
background=/usr/share/backgrounds/cat-login.jpg

-----------------------------------------------------
save file

2. bring your screen login to the folder /usr/share/backgrounds/

3. reboot

Ref:
Greeter

How to check if port is in use on Linux or Unix

sudo lsof -i -P -n | grep LISTEN
sudo netstat -tulpn | grep LISTEN
sudo lsof -i:22 ## see a specific port such as 22 ##
sudo nmap -sTU -O IP-address-Here

Option #1: lsof command
$ sudo lsof -i -P -n
$ sudo lsof -i -P -n | grep LISTEN
$ doas lsof -i -P -n | grep LISTEN ### [OpenBSD] ###

Linux netstat syntax
netstat -tulpn | grep LISTEN
watch netstat -tulpn
sudo ss -tulw
sudo ss -tulwn


netstat -tulpn |grep tcp |grep -v 127.0.0.1 |grep -v 192.168.101.36
-v is invert matching (every thing except 127.0.0.1 and 192.168.101.36)

Where ss command options are as follows:

• -t : Show only TCP sockets on Linux
• -u : Display only UDP sockets on Linux
• -l : Show listening sockets. For example, TCP port 22 is opened by SSHD server.
• -p : List process name that opened sockets
• -n : Don’t resolve service names i.e. don’t use DNS

FreeBSD/MacOS X netstat syntax

$ netstat -anp tcp | grep LISTEN
$ netstat -anp udp | grep LISTEN

OpenBSD netstat syntax

$ netstat -na -f inet | grep LISTEN
$ netstat -nat | grep LISTEN

Option #3: nmap command

The syntax is:
$ sudo nmap -sT -O localhost
$ sudo nmap -sU -O 192.168.2.13 ##[ list open UDP ports ]##
$ sudo nmap -sT -O 192.168.2.13 ##[ list open TCP ports ]##

You can combine TCP/UDP scan in a single command:
$ sudo nmap -sTU -O 192.168.2.13

A note about Windows users

You can check port usage from Windows operating system using following command:
netstat -bano | more
netstat -bano | grep LISTENING
netstat -bano | findstr /R /C:"[LISTEING]"

Ref:
unix-linux-check-if-port-is-in-use-command