Linux server cannot connect remotely

1. Check whether SSH is installed (check whether the SSH package is installed)

Enter the command:

rpm -qa | grep ssh

As shown below, the system has been installed by default SSH:

#If it is not installed, enter:

yum install openssh-server

to install it.

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2. Check whether the SSH service is running:

Enter the command:

/etc/init.d/shhd status

The above picture shows that the SSH service is started and running.

If it is not enabled, use the following command to enable it.

service shhd start

3. Check whether port 22 is open:

Use command:

netstat -anpt | grep sshd

-a List all options

-p Display and Process name and PID related to the connection

-t List TCP protocol connections

-u List UDP protocol connections

-n Disable reverse domain name resolution (by default netstat will use reverse domain name resolution technology to find the host name corresponding to each IP address. This will slow down the search speed. If you feel that the IP address is enough and there is no need to know the host name, use the -n option to disable the domain name resolution function)

The above picture shows that port 22 is open. If port 22 is not open, you can check whether the firewall is open:

Note: Basic operation commands of the firewall:

Query the firewall status:

[root@localhost ~]# service   iptables status

The red part on the way shows that port 22 is open. If port 22 of ssh is not opened, open /etc/sysconfig/iptables, add a column

-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT

Save and exit, and restart the firewall configuration.

4. Check whether SSHD is set to boot at this run level.

Enter the command:

chkconfig --list sshd

centos as shown in the figure The SSH server in the 6.5 system has been set to start at boot under this run level. If it is not set to start, use the following command:

5. After that, you can use remote Connection tool for remote connection.

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