记录：340

场景：在CentOS 7.9操作系统上，修改默认的ssh端口。ssh默认22端口，在实际开展业务中的生产环境中，通常会修改为指定端口号，以满足规范。

版本：

操作系统：CentOS 7.9

1.修改sshd_config配置文件

修改命令：vi /etc/ssh/sshd_config

修改内容：Port 10022

解析：在/etc/ssh/目录下，是ssh相关的配置信息。

2.重启sshd服务

重启命令：systemctl restart sshd

解析：修改端口后，需重启服务

3.查看端口信息

查看命令：netstat -atunlp | grep sshd

解析：使用netstat查看监听的端口和进程。

4.查看防火墙状态

查看状态：systemctl status firewalld

解析：查看防火墙状态，如果是Active: active (running)，则已经开启防火墙。如果是Active: inactive (dead)，则已关闭防火墙。

5.把端口10022添加到防火墙开放端口列表

添加端口：firewall-cmd --zone=public --add-port="10022"/tcp --permanent

解析：把10022端口持久化配置到开放端口列表中。

6.重新加载防火墙

命令：firewall-cmd --reload

解析：加载防火墙，使最新配置生效。

7.查看端口防火墙放行状态

命令：firewall-cmd --permanent --query-port="10022"/tcp

解析：查看端口防火墙已放行。

8.查看防火墙已放行的端口号列表

命令：firewall-cmd --zone=public --list-ports

解析：查看防火墙已放行的端口号列表。

9.使用Xshell客户端连接服务器

确认修改端口后，且开通防火墙后，可以使用Xshell等客户端工具连接服务器。

10.小结

(1)sshd服务支持配置多个端口号

ssh的配置文件sshd_config支持设置多个端口，比如22和10022可以都使用。

(2)确认新增端口可以使用后再关闭22端口

在实际工作中，确认新增端口可以使用后，再关闭22端口。因为一旦重启sshd服务后，22端口失效了。如果只修改了sshd端口，而没有开放防火墙，那么客户端是连接不上服务器。

这种情况，一旦发生，极有可能要到机房操作。一般而言，进机房审批流程等非常麻烦。因此，修改系统级别配置时，需多次自行确认无误，再下手操作。

11.附录sshd_config原始文件

命令：cat /etc/ssh/sshd_config

解析：查看原始文件，可以了解更多信息。

#	$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 yes

# 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 yes
#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

以上，感谢。

2022年11月27日