SSH - OpenSSH Server (sshd)

> SSH (Secure Shell) - Remote Access

1 - About

OpenSSH Server is a ssh server

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3 - Conf

3.1 - Default

/etc/default/ssh

3.2 - Set

The OpenSSH server reads a configuration file when it is started.

# Without arg, the conf file is located at /etc/ssh/sshd_config
sshd
# or with the f arg
sshd -f /path/to/conf/file

3.3 - Read

sshd -T

3.4 - Example

The system configuration file is /etc/ssh/sshd_config

It contains configuration data for sshd. The file format and configuration options are described in sshd_config(5).

/etc/ssh/sshd_config
# Package generated configuration file
# See the sshd_config(5) manpage for details
 
# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 2
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
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes
 
# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024
 
# Logging
SyslogFacility AUTH
LogLevel INFO
 
# Authentication:
LoginGraceTime 120
PermitRootLogin no
StrictModes yes
 
RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile	%h/.ssh/authorized_keys
 
# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes
 
# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no
 
# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no
 
# Change to no to disable tunnelled clear text passwords
PasswordAuthentication no
 
# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
 
# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
 
X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no
 
#MaxStartups 10:30:60
Banner /etc/azsec/banner.txt
# Allow client to pass locale environment variables
AcceptEnv LANG LC_*
 
Subsystem sftp /usr/lib/openssh/sftp-server
 
# 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
 
# CLOUD_IMG: This file was created/modified by the Cloud Image build process
ClientAliveInterval 120
Ciphers aes128-ctr,aes192-ctr,aes256-ctr

where:

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4 - Management

4.1 - Start

It is normally started at boot (init dameon dependent)

Example:

  • /etc/init.d/ssh
  • or /etc/init/ssh.conf (on systems using the Upstart init daemon)
/usr/sbin/sshd -D

4.2 - Pid

/var/run/sshd.pid

4.3 - Status

/sbin/service sshd status
systemdctl sshd status

4.4 - Start

/sbin/service sshd start
systemdctl sshd start
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4.5 - Test it

ssh -l user-name host-name

5 - Documentation / Reference

ssh/sshd.txt · Last modified: 2019/05/19 12:09 by gerardnico