[root@mail samba]# useradd -s /sbin/nologin -M sftp_user #创建一个系统用户，按需设置登录的shell和家目录

[root@mail samba]# passwd sftp_user  #设置密码，也是sftp登录的密码，公网上尽可能复杂点

[root@mail samba]# mkdir /var/sftp/sftp_user -pv  #创建sftp的根目录

[root@mail samba]# chown root:root -R  /var/sftp/sftp_user  #将属组和属主都设置为root，必须，这里最容易出错

[root@mail sftp_user]# cd /var/sftp/sftp_user/

[root@mail sftp_user]# mkdir public  #创建共享目录

[root@mail sftp_user]# chown sftp_user:sftp_user -R /var/sftp/sftp_user/public/  #将共享目录的属组属主设为我们的sftp用户

#   $OpenBSD: sshd_config,v 1.80 // :: djm Exp $

# This is the sshd server system-wide configuration file.  See

# sshd_config() for more information.

# This sshd was compiled with PATH=/usr/local/bin:/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 change a

# default value.

#Port

#AddressFamily any

#ListenAddress 0.0.0.0

#ListenAddress ::

# Disable legacy (protocol version ) support in the server for new

# installations. In future the default will change to require explicit

# activation of protocol

Protocol 2 #支持的SSH协议的版本号

# HostKey for protocol version

#HostKey /etc/ssh/ssh_host_key

# HostKeys for protocol version

#HostKey /etc/ssh/ssh_host_rsa_key

#HostKey /etc/ssh/ssh_host_dsa_key

# Lifetime and size of ephemeral version  server key

#KeyRegenerationInterval 1h

#ServerKeyBits 

# Logging

# obsoletes QuietMode and FascistLogging

#SyslogFacility AUTH

SyslogFacility AUTHPRIV   #将日志消息通过哪个日志子系统(facility)发送

#LogLevel INFO

# Authentication:

#LoginGraceTime 2m

#PermitRootLogin yes

#StrictModes yes

#MaxAuthTries

#MaxSessions 

#RSAAuthentication yes

#PubkeyAuthentication yes

#AuthorizedKeysFile .ssh/authorized_keys

#AuthorizedKeysCommand none

#AuthorizedKeysCommandRunAs nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts

#RhostsRSAAuthentication no

# similar for protocol version

#HostbasedAuthentication no

# Change to yes if you don't trust ~/.ssh/known_hosts for

# RhostsRSAAuthentication and 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 yes  #允许通过密码进行登录

# Change to no to disable s/key passwords

#ChallengeResponseAuthentication yes

ChallengeResponseAuthentication no  #是否允许质疑-应答(challenge-response)认证。默认值是"yes"。

# Kerberos options

#KerberosAuthentication no

#KerberosOrLocalPasswd yes

#KerberosTicketCleanup yes

#KerberosGetAFSToken no

#KerberosUseKuserok yes

# GSSAPI options

#GSSAPICleanupCredentials yes

GSSAPICleanupCredentials yes  #是否在用户退出登录后自动销毁用户凭证缓存。默认值是"yes"。仅用于SSH-2。

#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 no

UsePAM yes  #是否启用pam认证

# Accept locale-related environment variables

AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES  #指定客户端发送的哪些环境变量将会被传递到会话环境中。[注意]只有SSH-2协议支持环境变量的传递，可以设置多个

AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT

AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE

AcceptEnv XMODIFIERS

#AllowAgentForwarding yes

#AllowTcpForwarding yes

#GatewayPorts no

#X11Forwarding no

X11Forwarding yes  #是否允许进行 X11 转发。默认值是"no"，设为"yes"表示允许

#X11DisplayOffset

#X11UseLocalhost yes

#PrintMotd yes

#PrintLastLog yes

#TCPKeepAlive yes

#UseLogin no

#UsePrivilegeSeparation yes

#PermitUserEnvironment no

#Compression delayed

#ClientAliveInterval

#ClientAliveCountMax

#ShowPatchLevel no

#PidFile /var/run/sshd.pid

#MaxStartups ::

#PermitTunnel no

#ChrootDirectory none

# no default banner path

#Banner none

# override default of no subsystems

#Subsystem  sftp    /usr/libexec/openssh/sftp-server

Subsystem       sftp    internal-sftp    #配置一个外部子系统，仅用于SSH-2协议。值是一个子系统的名字和对应的命令行(含选项和参数)。比如"sftp /usr/libexec/openssh/sftp-server"。，###这里配置为内部的

# Example of overriding settings on a per-user basis

#Match User anoncvs

#   X11Forwarding no

#   AllowTcpForwarding no

#   ForceCommand cvs server

GSSAPIAuthentication no #是否允许使用基于 GSSAPI 的用户认证。默认值为"no"。仅用于SSH-2。

UseDNS no   #是否对远程主机名进行反向解析

AllowTcpForwarding yes   #是否允许TCP转发

Compression yes #是否对通信数据进行加密，还是延迟到认证成功之后再对通信数据加密

MaxAuthTries 6  #指定每个连接最大允许的认证次数。默认值是 6

PermitRootLogin yes  #是否允许 root 登录

PrintMotd yes  #是否在每一次交互式登录时打印 /etc/motd 文件的内容

PubkeyAuthentication yes  #是否允许公钥认证。仅可以用于SSH-2。默认值为"yes"。

RSAAuthentication no  #是否允许使用纯 RSA 公钥认证。仅用于SSH-1。默认值是"yes"

Match User sftp_user  #对特定的用户单独配置，匹配到的用户会强制使用/bin/false shell,只能以sftp登录，无法使用ssh登录服务器，没有匹配到的用户或组可以直接sftp登录，但是根目录为自己的家目录，无法指定具体的根目录。也可以设置为组，例如：Match Group sftp 

ChrootDirectory   /var/sftp/sftp_user/  #限定用户的根目录

X11Forwarding no

AllowTcpForwarding yes

ForceCommand internal-sftp  #强制执行这里指定的命令而忽略客户端提供的任何命令

[root@mail sftp_user]# /etc/init.d/sshd restart

停止 sshd：                                                [确定]

正在启动 sshd：                                          [确定]