SSH, or Secure Shell, is a protocol used to securely log onto
remote systems. It is the most common way to access remote Linux and
Unix-like servers.
in this blog I am explain to create ssh pem key for login on remote server and disable password authentication.
in this blog I am explain to create ssh pem key for login on remote server and disable password authentication.
1. Create SSH Key
for User user
Generating
public/private rsa key pair.
Enter file in which
to save the key (/root/.ssh/id_rsa):
Enter passphrase
(empty for no passphrase):
Enter same
passphrase again:
Your identification
has been saved in /root/.ssh/centos.
Your public key has
been saved in /root/.ssh/centos.pub.
The key fingerprint
is:
SHA256:nyvUUxXSRpqpAkydVjoF9RS1Kyz1WOA6Q8THNWV+rTw
root@sshserver.example.com
The key's randomart
image is:
+---[RSA 2048]----+
| ...*=.=**oo|
| o ++.+o*+=.|
| o.o ..Boo +|
| . o =.= o.|
| S.*.+ E |
| .oo= . . |
| . o. |
| . . |
| .. |
+----[SHA256]-----+
[root@sshserver ~]#
cd /root/.ssh/
2. copy centos.pub key in authorized_keys file.
[root@sshserver ~]#
cp ~/.ssh id_rsa.pub >> authorized_keys
3. Move centos private key into centos.pem key
[root@sshserver ~]# mv id_rsa.pub centos.pub
[root@sshserver ~]# mv id_rsa centos.pem
[root@sshserver ~]# mv id_rsa.pub centos.pub
[root@sshserver ~]# mv id_rsa centos.pem
[root@sshserver ~]#
ls -l .ssh/
total 16
-rw-------. 1 root
root 616 May 16 13:33 authorized_keys
-rw-------. 1 root
root 668 May 16 13:33 centos.pem
-rw-r--r--. 1 root
root 616 May 16 13:33 centos.pub
-rw-r--r--. 1 root
root 175 May 16 13:35 known_hosts
[root@sshserver ~]#
4. Now change below configure in sshd_config file.
[root@sshserver ~]#
vim /etc/ssh/sshd_config
[root@sshserver ~]#
cat /etc/ssh/sshd_config
# $OpenBSD:
sshd_config,v 1.100 2016/08/15 12:32:04 naddy Exp $
# This is the sshd
server system-wide configuration file. See
# sshd_config(5) for
more information.
# This sshd was
compiled with PATH=/usr/local/bin:/usr/bin
# 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.
# If you want to
change the port on a SELinux system, you have to tell
# SELinux about this
change.
# semanage port -a
-t ssh_port_t -p tcp #PORTNUMBER
#
#Port 22
#AddressFamily any
#ListenAddress
0.0.0.0
#ListenAddress ::
HostKey
/etc/ssh/ssh_host_rsa_key
#HostKey
/etc/ssh/ssh_host_dsa_key
HostKey
/etc/ssh/ssh_host_ecdsa_key
HostKey
/etc/ssh/ssh_host_ed25519_key
# Ciphers and keying
#RekeyLimit default
none
# Logging
#SyslogFacility AUTH
SyslogFacility
AUTHPRIV
#LogLevel INFO
# Authentication:
#LoginGraceTime 2m
#PermitRootLogin yes
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10
PubkeyAuthentication
yes
# The default is to
check both .ssh/authorized_keys and .ssh/authorized_keys2
# but this is
overridden so installations will only check .ssh/authorized_keys
AuthorizedKeysFile .ssh/authorized_keys
#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
yes
#PermitEmptyPasswords
no
PasswordAuthentication
no
# Change to no to
disable s/key passwords
#ChallengeResponseAuthentication
yes
ChallengeResponseAuthentication
no
# Kerberos options
#KerberosAuthentication
no
#KerberosOrLocalPasswd
yes
#KerberosTicketCleanup
yes
#KerberosGetAFSToken
no
#KerberosUseKuserok
yes
# GSSAPI options
GSSAPIAuthentication
yes
GSSAPICleanupCredentials
no
#GSSAPIStrictAcceptorCheck
yes
#GSSAPIKeyExchange
no
#GSSAPIEnablek5users
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'.
# WARNING: 'UsePAM
no' is not supported in Red Hat Enterprise Linux and may cause
several
# problems.
UsePAM yes
#AllowAgentForwarding
yes
#AllowTcpForwarding
yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation
sandbox
#PermitUserEnvironment
no
#Compression delayed
#ClientAliveInterval
0
#ClientAliveCountMax
3
#ShowPatchLevel no
#UseDNS no
#PidFile
/var/run/sshd.pid
#MaxStartups
10:30:100
#PermitTunnel no
#ChrootDirectory
none
#VersionAddendum
none
# no default banner
path
#Banner none
# Accept
locale-related environment variables
AcceptEnv LANG
LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER
LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv
LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS
# override default
of no subsystems
Subsystem sftp /usr/libexec/openssh/sftp-server
# Example of
overriding settings on a per-user basis
#Match User anoncvs
# X11Forwarding no
# AllowTcpForwarding
no
# PermitTTY no
# ForceCommand cvs
server
[root@sshserver ~]#
5. After changing above configure in sshd_config we need to restart sshd service.
[root@sshserver ~]#service sshd restart
6. Now copy ssh key pem file to remote server via scp command
[root@sshserver ~]#
scp centos.pem user@remote.server:/home/user
7. Now try ssh with -i option in ssh server without enter password.
[root@remote ~]#
scp -i /home/user/centos.pem root@sshserver.example.com
Enjoy.
