[troubleshooting] what if SFTP cannot connect to the server?

Today, when I transferred a file on a springboard machine, I found that when I used SFTP to connect, there was such a rejection:

Log in to the jump machine, use # tail / var/log/secure, and see the specific information of rejection, as follows:

At this point, I need # locate sftp-server to locate the sftp file with locate, only to find that the server answered me "- bash: locate: command not found".

So # yum-y install mlocate, execute updatedb after installing mlocate, wait a while, and then execute # locate sftp-server again to get the file path of sftp-server, as shown below:

Open the configuration file for sshd, # vi / etc/ssh/sshd_config, and remove the # in front of the Subsystem line:

Then restart and start the ssh service with the statement # / etc/init.d/sshd reload, reconnect and find that it is back to normal.