cat /etc/ssh/sshd_config

#	$OpenBSD: sshd_config,v 1.101 2017/03/14 07:19:07 djm Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key

# Ciphers and keying
#RekeyLimit default none

# Logging
#SyslogFacility AUTH
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#PubkeyAuthentication yes

# Expect .ssh/authorized_keys2 to be disregarded by default in future.
#AuthorizedKeysFile	.ssh/authorized_keys .ssh/authorized_keys2

#AuthorizedPrincipalsFile none

#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
PasswordAuthentication no
#PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
PrintMotd no
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none

# no default banner path
#Banner none

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

# override default of no subsystems
Subsystem	sftp	/usr/lib/openssh/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#	X11Forwarding no
#	AllowTcpForwarding no
#	PermitTTY no
#	ForceCommand cvs server

#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key

head -1 ~/.ssh/known_hosts

github.com,192.30.255.113 ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ==

ssh-keygen -t ed25519 -f ~/.ssh/id_sample

Generating public/private ed25519 key pair.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/wand/.ssh/id_sample.
Your public key has been saved in /home/wand/.ssh/id_sample.pub.
The key fingerprint is:
SHA256:zmuiudfSAw7bXap1j5rHnfj0pWMUWSkM1zsWxt1jKPc wand@lpic2-study-1
The key's randomart image is:
+--[ED25519 256]--+
|           .o.+ +|
|           ..= O+|
|            o =o+|
|              oE |
|        S     ...|
|    . .o  .   .  |
|     = =++.o.o  .|
|    ..*.B+++o.oo |
|    ++.=++..o.o. |
+----[SHA256]-----+

ssh-keygen -p -P hoge -N piyo -f ~/.ssh/id_sample

Key has comment 'wand@lpic2-study-1'
Your identification has been saved with the new passphrase.

ssh-keygen -l -f ~/.ssh/id_sample

256 SHA256:zmuiudfSAw7bXap1j5rHnfj0pWMUWSkM1zsWxt1jKPc wand@lpic2-study-1 (ED25519)

ssh-keygen -R ホスト

ssh-agent bash

command="コマンド" ssh-rsa AAAAB...
from="ネットワーク" ssh-rsa AAAAB...
no-X11-forwarding ssh-rsa AAAAB...

ssh -L 13306:db_host:3306 ssh_user@bastion

mysql -h 127.0.0.1 -P 13306 -u db_user -p

Protocol 2

PasswordAuthentication no

PermitRootLogin no

ldd $(which sshd) | grep libwrap

	libwrap.so.0 => /lib64/libwrap.so.0 (0x00007f5564405000)

sshd: 172.16.

sshd: ALL

yum provides fail2ban

Failed to set locale, defaulting to C
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: ty1.mirror.newmediaexpress.com
 * epel: d2lzkl7pfhq30w.cloudfront.net
 * extras: ty1.mirror.newmediaexpress.com
 * updates: ty1.mirror.newmediaexpress.com
google-cloud-sdk                                                                                      974/974
fail2ban-0.11.1-10.el7.noarch : Daemon to ban hosts that cause multiple authentication errors
Repo        : epel

sudo yum -y install nmap

sudo nmap localhost

Starting Nmap 6.40 ( http://nmap.org ) at 2021-01-07 16:22 UTC
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000019s latency).
Other addresses for localhost (not scanned): 127.0.0.1
Not shown: 997 closed ports
PORT    STATE SERVICE
22/tcp  open  ssh
25/tcp  open  smtp
111/tcp open  rpcbind

Nmap done: 1 IP address (1 host up) scanned in 1.62 seconds

sudo nmap -sX localhost

Starting Nmap 6.40 ( http://nmap.org ) at 2021-01-07 16:24 UTC
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000098s latency).
Other addresses for localhost (not scanned): 127.0.0.1
Not shown: 997 closed ports
PORT    STATE         SERVICE
22/tcp  open|filtered ssh
25/tcp  open|filtered smtp
111/tcp open|filtered rpcbind

Nmap done: 1 IP address (1 host up) scanned in 96.66 seconds

sudo netstat -atun

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN     
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:49145           0.0.0.0:*               LISTEN     
tcp        0      0 10.146.0.4:22           xx.xx.xx.xx:59862    ESTABLISHED
tcp        0      0 10.146.0.4:44854        169.254.169.254:80      ESTABLISHED
tcp        0      0 10.146.0.4:22           xx.xx.xx.xx:59832    ESTABLISHED
tcp        0      0 10.146.0.4:44862        169.254.169.254:80      ESTABLISHED
tcp        0      0 10.146.0.4:60018        172.217.26.42:443       ESTABLISHED
tcp        0      0 10.146.0.4:33622        172.217.161.74:443      ESTABLISHED
tcp6       0      0 :::39753                :::*                    LISTEN     
tcp6       0      0 :::111                  :::*                    LISTEN     
tcp6       0      0 :::22                   :::*                    LISTEN     
tcp6       0      0 ::1:25                  :::*                    LISTEN     
udp        0      0 0.0.0.0:623             0.0.0.0:*                          
udp        0      0 0.0.0.0:111             0.0.0.0:*                          
udp        0      0 127.0.0.1:659           0.0.0.0:*                          
udp        0      0 127.0.0.1:323           0.0.0.0:*                          
udp        0      0 0.0.0.0:33285           0.0.0.0:*                          
udp        0      0 0.0.0.0:68              0.0.0.0:*                          
udp6       0      0 :::623                  :::*                               
udp6       0      0 :::111                  :::*                               
udp6       0      0 ::1:323                 :::*                               
udp6       0      0 :::46532                :::*                               

ss -atun

Netid  State      Recv-Q Send-Q       Local Address:Port                      Peer Address:Port              
udp    UNCONN     0      0                        *:623                                  *:*                  
udp    UNCONN     0      0                        *:111                                  *:*                  
udp    UNCONN     0      0                127.0.0.1:659                                  *:*                  
udp    UNCONN     0      0                127.0.0.1:323                                  *:*                  
udp    UNCONN     0      0                        *:33285                                *:*                  
udp    UNCONN     0      0                        *:68                                   *:*                  
udp    UNCONN     0      0                     [::]:623                               [::]:*                  
udp    UNCONN     0      0                     [::]:111                               [::]:*                  
udp    UNCONN     0      0                    [::1]:323                               [::]:*                  
udp    UNCONN     0      0                     [::]:46532                             [::]:*                  
tcp    LISTEN     0      128                      *:111                                  *:*                  
tcp    LISTEN     0      128                      *:22                                   *:*                  
tcp    LISTEN     0      100              127.0.0.1:25                                   *:*                  
tcp    LISTEN     0      128                      *:49145                                *:*                  
tcp    ESTAB      0      1148            10.146.0.4:22                      xx.xx.xx.xx:59862              
tcp    ESTAB      0      0               10.146.0.4:44854                  169.254.169.254:80                 
tcp    ESTAB      0      0               10.146.0.4:22                      xx.xx.xx.xx:59832              
tcp    ESTAB      0      0               10.146.0.4:44862                  169.254.169.254:80                 
tcp    ESTAB      0      0               10.146.0.4:60018                    172.217.26.42:443                
tcp    ESTAB      0      0               10.146.0.4:33622                   172.217.161.74:443                
tcp    LISTEN     0      128                   [::]:39753                             [::]:*                  
tcp    LISTEN     0      128                   [::]:111                               [::]:*                  
tcp    LISTEN     0      128                   [::]:22                                [::]:*                  
tcp    LISTEN     0      100                  [::1]:25                                [::]:*                  

sudo lsof -i -n

COMMAND    PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
rpcbind    460     rpc    6u  IPv4  14770      0t0  UDP *:sunrpc 
rpcbind    460     rpc    7u  IPv4  14820      0t0  UDP *:asf-rmcp 
rpcbind    460     rpc    8u  IPv4  14821      0t0  TCP *:sunrpc (LISTEN)
rpcbind    460     rpc    9u  IPv6  14822      0t0  UDP *:sunrpc 
rpcbind    460     rpc   10u  IPv6  14823      0t0  UDP *:asf-rmcp 
rpcbind    460     rpc   11u  IPv6  14824      0t0  TCP *:sunrpc (LISTEN)
chronyd    475  chrony    5u  IPv4  15105      0t0  UDP 127.0.0.1:323 
chronyd    475  chrony    6u  IPv6  15106      0t0  UDP [::1]:323 
dhclient   645    root    6u  IPv4  16617      0t0  UDP *:bootpc 
google_os  879    root    3u  IPv4  18661      0t0  TCP 10.146.0.4:44854->169.254.169.254:http (ESTABLISHED)
google_os  879    root    6u  IPv4  52750      0t0  TCP 10.146.0.4:48040->216.58.197.170:https (ESTABLISHED)
rpc.statd  888 rpcuser    7u  IPv4  18461      0t0  UDP *:33285 
rpc.statd  888 rpcuser    8u  IPv4  18468      0t0  TCP *:49145 (LISTEN)
rpc.statd  888 rpcuser    9u  IPv6  18472      0t0  UDP *:46532 
rpc.statd  888 rpcuser   10u  IPv6  18476      0t0  TCP *:39753 (LISTEN)
rpc.statd  888 rpcuser   25u  IPv4  17227      0t0  UDP 127.0.0.1:659 
google_gu  902    root    3u  IPv4  18675      0t0  TCP 10.146.0.4:44862->169.254.169.254:http (ESTABLISHED)
google_gu  902    root    6u  IPv4  52066      0t0  TCP 10.146.0.4:37878->216.58.220.106:https (ESTABLISHED)
master    1034    root   13u  IPv4  18244      0t0  TCP 127.0.0.1:smtp (LISTEN)
master    1034    root   14u  IPv6  18245      0t0  TCP [::1]:smtp (LISTEN)
sshd      1241    root    3u  IPv4  19520      0t0  TCP *:ssh (LISTEN)
sshd      1241    root    4u  IPv6  19522      0t0  TCP *:ssh (LISTEN)
sshd      2702    root    3u  IPv4  40897      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59832 (ESTABLISHED)
sshd      2705    wand    3u  IPv4  40897      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59832 (ESTABLISHED)
sshd      3341    root    3u  IPv4  48914      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59862 (ESTABLISHED)
sshd      3344    wand    3u  IPv4  48914      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59862 (ESTABLISHED)

sudo lsof -i:22 -n

COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
sshd    1241 root    3u  IPv4  19520      0t0  TCP *:ssh (LISTEN)
sshd    1241 root    4u  IPv6  19522      0t0  TCP *:ssh (LISTEN)
sshd    2702 root    3u  IPv4  40897      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59832 (ESTABLISHED)
sshd    2705 wand    3u  IPv4  40897      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59832 (ESTABLISHED)
sshd    3341 root    3u  IPv4  48914      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59862 (ESTABLISHED)
sshd    3344 wand    3u  IPv4  48914      0t0  TCP 10.146.0.4:ssh->xx.xx.xx.xx:59862 (ESTABLISHED)

sudo fuser -v -n tcp 22

                     USER        PID ACCESS COMMAND
22/tcp:              root       1241 F.... sshd
                     root       2702 F.... sshd
                     wand       2705 F.... sshd
                     root       3341 F.... sshd
                     wand       3344 F.... sshd

ALL: .friendly.domain: ALLOW
ALL: ALL: DENY

ALL: .bad.domain: DENY
ALL: ALL: ALLOW

sshd: LOCAL

ALL:ALL:spawn (/some/where/safe_finger -l @%h | /usr/ucb/mail root) &

in.ftpd : ... : twist /bin/echo 421 Some bounce message
in.telnetd : ... : twist PATH=/some/other; exec in.telnetd

type ls

ls is /usr/bin/ls

type echo

echo is a shell builtin

echo *

Maildir httpd ldap lo public_html tmp

rpm -Va

...
..?......  c /etc/sysconfig/sshd
S.5....T.  c /etc/sysconfig/authconfig
S.5....T.  c /etc/postfix/main.cf
S.5....T.  c /etc/chrony.conf
missing     /etc/dhcp/dhclient.d/chrony.sh (Permission denied)
...
.M.......  g /var/lock/iscsi
...
....L....  c /etc/pam.d/fingerprint-auth

sudo yum -y install openvpn

sudo yum -y install openvpn

sudo ls -lR /etc/openvpn/

/etc/openvpn/:
total 0
drwxr-x---. 2 root openvpn 6 Dec  9 16:57 client
drwxr-x---. 2 root openvpn 6 Dec  9 16:57 server

/etc/openvpn/client:
total 0

/etc/openvpn/server:
total 0

sudo curl -L https://github.com/OpenVPN/easy-rsa/archive/v2.2.0.tar.gz -o v2.2.0.tar.gz
sudo tar xvzf v2.2.0.tar.gz

cd /etc/openvpn/easy-rsa-2.2.0/easy-rsa/2.0

ls

build-ca     build-key-pass    build-req-pass  openssl-0.9.6.cnf  revoke-full
build-dh     build-key-pkcs12  clean-all       openssl-0.9.8.cnf  sign-req
build-inter  build-key-server  inherit-inter   openssl-1.0.0.cnf  vars
build-key    build-req	       list-crl        pkitool		  whichopensslcnf

cat vars

# easy-rsa parameter settings

# NOTE: If you installed from an RPM,
# don't edit this file in place in
# /usr/share/openvpn/easy-rsa --
# instead, you should copy the whole
# easy-rsa directory to another location
# (such as /etc/openvpn) so that your
# edits will not be wiped out by a future
# OpenVPN package upgrade.

# This variable should point to
# the top level of the easy-rsa
# tree.
export EASY_RSA="`pwd`"

#
# This variable should point to
# the requested executables
#
export OPENSSL="openssl"
export PKCS11TOOL="pkcs11-tool"
export GREP="grep"


# This variable should point to
# the openssl.cnf file included
# with easy-rsa.
export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`

# Edit this variable to point to
# your soon-to-be-created key
# directory.
#
# WARNING: clean-all will do
# a rm -rf on this directory
# so make sure you define
# it correctly!
export KEY_DIR="$EASY_RSA/keys"

# Issue rm -rf warning
echo NOTE: If you run ./clean-all, I will be doing a rm -rf on $KEY_DIR

# PKCS11 fixes
export PKCS11_MODULE_PATH="dummy"
export PKCS11_PIN="dummy"

# Increase this to 2048 if you
# are paranoid.  This will slow
# down TLS negotiation performance
# as well as the one-time DH parms
# generation process.
export KEY_SIZE=1024

# In how many days should the root CA key expire?
export CA_EXPIRE=3650

# In how many days should certificates expire?
export KEY_EXPIRE=3650

# These are the default values for fields
# which will be placed in the certificate.
# Don't leave any of these fields blank.
export KEY_COUNTRY="US"
export KEY_PROVINCE="CA"
export KEY_CITY="SanFrancisco"
export KEY_ORG="Fort-Funston"
export KEY_EMAIL="me@myhost.mydomain"
export KEY_EMAIL=mail@host.domain
export KEY_CN=changeme
export KEY_NAME=changeme
export KEY_OU=changeme
export PKCS11_MODULE_PATH=changeme
export PKCS11_PIN=1234

export KEY_COUNTRY="JP"
export KEY_PROVINCE="TOKYO"
export KEY_CITY="Shinjuku"
export KEY_ORG="LPIC"
export KEY_EMAIL="me@myhost.mydomain"
export KEY_EMAIL=mail@host.domain
export KEY_CN=changeme
export KEY_NAME=changeme
export KEY_OU=changeme
export PKCS11_MODULE_PATH=changeme
export PKCS11_PIN=1234

sudo -i

# cd /etc/openvpn/easy-rsa-2.2.0/easy-rsa/2.0
# . vars

NOTE: If you run ./clean-all, I will be doing a rm -rf on /etc/openvpn/easy-rsa-2.2.0/easy-rsa/2.0/keys

# ./clean-all

Please source the vars script first (i.e. "source ./vars")
Make sure you have edited it to reflect your configuration.

# ./build-ca

Generating a 1024 bit RSA private key
...............++++++
....++++++
writing new private key to 'ca.key'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [JP]:
State or Province Name (full name) [TOKYO]:
Locality Name (eg, city) [Shinjuku]:
Organization Name (eg, company) [LPIC]:
Organizational Unit Name (eg, section) [changeme]:
Common Name (eg, your name or your server's hostname) [changeme]:
Name [changeme]:
Email Address [mail@host.domain]:

ls keys

ca.crt	ca.key	index.txt  serial

# ./build-key-server server

Generating a 1024 bit RSA private key
..............................++++++
........................++++++
writing new private key to 'server.key'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [JP]:
State or Province Name (full name) [TOKYO]:
Locality Name (eg, city) [Shinjuku]:
Organization Name (eg, company) [LPIC]:
Organizational Unit Name (eg, section) [changeme]:
Common Name (eg, your name or your server's hostname) [server]:
Name [changeme]:
Email Address [mail@host.domain]:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
Using configuration from /etc/openvpn/easy-rsa-2.2.0/easy-rsa/2.0/openssl-1.0.0.cnf
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
countryName           :PRINTABLE:'JP'
stateOrProvinceName   :PRINTABLE:'TOKYO'
localityName          :PRINTABLE:'Shinjuku'
organizationName      :PRINTABLE:'LPIC'
organizationalUnitName:PRINTABLE:'changeme'
commonName            :PRINTABLE:'server'
name                  :PRINTABLE:'changeme'
emailAddress          :IA5STRING:'mail@host.domain'
Certificate is to be certified until Jan  6 17:17:53 2031 GMT (3650 days)
Sign the certificate? [y/n]:y


1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated

ls keys

01.pem	ca.key	   index.txt.attr  serial      server.crt  server.key
ca.crt	index.txt  index.txt.old   serial.old  server.csr

# ./build-dh

Generating DH parameters, 1024 bit long safe prime, generator 2
This is going to take a long time
......................+............... ...

ls keys

01.pem	ca.key	    index.txt	    index.txt.old  serial.old  server.csr
ca.crt	dh1024.pem  index.txt.attr  serial	   server.crt  server.key

# ./build-key client

Generating a 1024 bit RSA private key
..........++++++
.....++++++
writing new private key to 'client.key'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [JP]:
State or Province Name (full name) [TOKYO]:
Locality Name (eg, city) [Shinjuku]:
Organization Name (eg, company) [LPIC]:
Organizational Unit Name (eg, section) [changeme]:
Common Name (eg, your name or your server's hostname) [client]:
Name [changeme]:
Email Address [mail@host.domain]:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
Using configuration from /etc/openvpn/easy-rsa-2.2.0/easy-rsa/2.0/openssl-1.0.0.cnf
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
countryName           :PRINTABLE:'JP'
stateOrProvinceName   :PRINTABLE:'TOKYO'
localityName          :PRINTABLE:'Shinjuku'
organizationName      :PRINTABLE:'LPIC'
organizationalUnitName:PRINTABLE:'changeme'
commonName            :PRINTABLE:'client'
name                  :PRINTABLE:'changeme'
emailAddress          :IA5STRING:'mail@host.domain'
Certificate is to be certified until Jan  6 17:25:15 2031 GMT (3650 days)
Sign the certificate? [y/n]:y


1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
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ls /usr/share/doc/openvpn-2.4.10/sample/sample-scripts

auth-pam.pl  bridge-start  bridge-stop	ucn.pl	verify-cn

cat /usr/share/doc/openvpn-2.4.10/sample/sample-scripts/bridge-start

#!/bin/sh

#################################
# Set up Ethernet bridge on Linux
# Requires: bridge-utils
#################################

# Define Bridge Interface
br="br0"

# Define list of TAP interfaces to be bridged,
# for example tap="tap0 tap1 tap2".
tap="tap0"

# Define physical ethernet interface to be bridged
# with TAP interface(s) above.
eth="eth0"
eth_ip="192.168.8.4"
eth_netmask="255.255.255.0"
eth_broadcast="192.168.8.255"

for t in $tap; do
    openvpn --mktun --dev $t
done

brctl addbr $br
brctl addif $br $eth

for t in $tap; do
    brctl addif $br $t
done

for t in $tap; do
    ifconfig $t 0.0.0.0 promisc up
done

ifconfig $eth 0.0.0.0 promisc up

ifconfig $br $eth_ip netmask $eth_netmask broadcast $eth_broadcast

cat /usr/share/doc/openvpn-2.4.10/sample/sample-scripts/bridge-stop

#!/bin/sh

####################################
# Tear Down Ethernet bridge on Linux
####################################

# Define Bridge Interface
br="br0"

# Define list of TAP interfaces to be bridged together
tap="tap0"

ifconfig $br down
brctl delbr $br

for t in $tap; do
    openvpn --rmtun --dev $t
done

ls /usr/share/doc/openvpn-2.4.10/sample/

sample-config-files  sample-scripts  sample-windows

ls /usr/share/doc/openvpn-2.4.10/sample/sample-config-files/

README		 office.up		  static-home.conf
client.conf	 openvpn-shutdown.sh	  static-office.conf
firewall.sh	 openvpn-startup.sh	  tls-home.conf
home.up		 roadwarrior-client.conf  tls-office.conf
loopback-client  roadwarrior-server.conf  xinetd-client-config
loopback-server  server.conf		  xinetd-server-config

cat /usr/share/doc/openvpn-2.4.10/sample/sample-config-files/server.conf

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#                                               #
# This file is for the server side              #
# of a many-clients <-> one-server              #
# OpenVPN configuration.                        #
#                                               #
# OpenVPN also supports                         #
# single-machine <-> single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#                                               #
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#                                               #
# Comments are preceded with '#' or ';'         #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
;proto tcp
proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one.  On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca ca.crt
cert server.crt
key server.key  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh2048.pem 2048
dh dh2048.pem

# Network topology
# Should be subnet (addressing via IP)
# unless Windows clients v2.0.9 and lower have to
# be supported (then net30, i.e. a /30 per client)
# Defaults to net30 (not recommended)
;topology subnet

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.0 255.255.255.0

# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses.  You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.10.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
;push "redirect-gateway def1 bypass-dhcp"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
;push "dhcp-option DNS 208.67.222.222"
;push "dhcp-option DNS 208.67.220.220"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
;client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
tls-auth ta.key 0 # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
cipher AES-256-CBC

# Enable compression on the VPN link and push the
# option to the client (v2.4+ only, for earlier
# versions see below)
;compress lz4-v2
;push "compress lz4-v2"

# For compression compatible with older clients use comp-lzo
# If you enable it here, you must also
# enable it in the client config file.
;comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nobody

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         openvpn.log
;log-append  openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

# Notify the client that when the server restarts so it
# can automatically reconnect.

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
;proto tcp
proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca ca.crt
cert server.crt
key server.key  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh2048.pem 2048
dh dh2048.pem

# Enable compression on the VPN link and push the
# option to the client (v2.4+ only, for earlier
# versions see below)
;compress lz4-v2
;push "compress lz4-v2"

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nobody

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         openvpn.log
;log-append  openvpn.log

cat /usr/share/doc/openvpn-2.4.10/sample/sample-config-files/client.conf

##############################################
# Sample client-side OpenVPN 2.0 config file #
# for connecting to multi-client server.     #
#                                            #
# This configuration can be used by multiple #
# clients, however each client should have   #
# its own cert and key files.                #
#                                            #
# On Windows, you might want to rename this  #
# file so it has a .ovpn extension           #
##############################################

# Specify that we are a client and that we
# will be pulling certain config file directives
# from the server.
client

# Use the same setting as you are using on
# the server.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel
# if you have more than one.  On XP SP2,
# you may need to disable the firewall
# for the TAP adapter.
;dev-node MyTap

# Are we connecting to a TCP or
# UDP server?  Use the same setting as
# on the server.
;proto tcp
proto udp

# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote my-server-1 1194
;remote my-server-2 1194

# Choose a random host from the remote
# list for load-balancing.  Otherwise
# try hosts in the order specified.
;remote-random

# Keep trying indefinitely to resolve the
# host name of the OpenVPN server.  Very useful
# on machines which are not permanently connected
# to the internet such as laptops.
resolv-retry infinite

# Most clients don't need to bind to
# a specific local port number.
nobind

# Downgrade privileges after initialization (non-Windows only)
;user nobody
;group nobody

# Try to preserve some state across restarts.
persist-key
persist-tun

# If you are connecting through an
# HTTP proxy to reach the actual OpenVPN
# server, put the proxy server/IP and
# port number here.  See the man page
# if your proxy server requires
# authentication.
;http-proxy-retry # retry on connection failures
;http-proxy [proxy server] [proxy port #]

# Wireless networks often produce a lot
# of duplicate packets.  Set this flag
# to silence duplicate packet warnings.
;mute-replay-warnings

# SSL/TLS parms.
# See the server config file for more
# description.  It's best to use
# a separate .crt/.key file pair
# for each client.  A single ca
# file can be used for all clients.
ca ca.crt
cert client.crt
key client.key

# Verify server certificate by checking that the
# certicate has the correct key usage set.
# This is an important precaution to protect against
# a potential attack discussed here:
#  http://openvpn.net/howto.html#mitm
#
# To use this feature, you will need to generate
# your server certificates with the keyUsage set to
#   digitalSignature, keyEncipherment
# and the extendedKeyUsage to
#   serverAuth
# EasyRSA can do this for you.
remote-cert-tls server

# If a tls-auth key is used on the server
# then every client must also have the key.
tls-auth ta.key 1

# Select a cryptographic cipher.
# If the cipher option is used on the server
# then you must also specify it here.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
cipher AES-256-CBC

# Enable compression on the VPN link.
# Don't enable this unless it is also
# enabled in the server config file.
#comp-lzo

# Set log file verbosity.
verb 3

# Silence repeating messages
;mute 20

# Specify that we are a client and that we
# will be pulling certain config file directives
# from the server.
client

# Are we connecting to a TCP or
# UDP server?  Use the same setting as
# on the server.
;proto tcp
proto udp

# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote my-server-1 1194
;remote my-server-2 1194

# SSL/TLS parms.
# See the server config file for more
# description.  It's best to use
# a separate .crt/.key file pair
# for each client.  A single ca
# file can be used for all clients.
ca ca.crt
cert client.crt
key client.key

# /usr/sbin/openvpn /etc/openvpn/client.conf