关闭TCP 25 端口对应的服务
[0 root@Qvps /root] #cat /etc/centos-release
CentOS Linux release 7.9.2009 (Core)
[0 root@Qvps /root] #uname -r
3.10.0-1160.el7.x86_64
1. 确认对应端口的进程
#ss -ntl
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 100 127.0.0.1:25 *:*
LISTEN 0 128 *:22 *:*
LISTEN 0 100 [::1]:25 [::]:*
LISTEN 0 128 [::]:22 [::]:*
#netstat -antlp | grep 25
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 695/master
tcp6 0 0 ::1:25 :::* LISTEN 695/master
[0 root@Qvps /data] #ps aux | grep 695
root 695 0.0 0.1 89708 2076 ? Ss 08:34 0:00 /usr/libexec/postfix/master -w
root 13526 0.0 0.0 112816 944 pts/0 S+ 09:26 0:00 grep --color=auto 695
# rpm -qf '/usr/libexec/postfix/master'
postfix-2.10.1-9.el7.x86_64
2. 查找与关闭对应服务
# chkconfig --list
Note: This output shows SysV services only and does not include native
systemd services. SysV configuration data might be overridden by native
systemd configuration.
If you want to list systemd services use 'systemctl list-unit-files'.
To see services enabled on particular target use
'systemctl list-dependencies [target]'.
netconsole 0:off 1:off 2:off 3:off 4:off 5:off 6:off
network 0:off 1:off 2:off 3:off 4:off 5:off 6:off
#systemctl list-unit-files | grep post
postfix.service enabled
#systemctl disable --now postfix.service
Removed symlink /etc/systemd/system/multi-user.target.wants/postfix.service.
3. 确认结果，端口已关闭
[0 root@Qvps /data] #systemctl list-unit-files | grep postfix
postfix.service disabled
[0 root@Qvps /data] #ps aux | grep postf
root 13743 0.0 0.0 112812 944 pts/0 S+ 09:29 0:00 grep --color=auto postf
[0 root@Qvps /data] #ss -ntl
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:22 *:*
LISTEN 0 128 [::]:22 [::]:*