Contents
1.Setting up SSH remote connection
SSH is a service to connect to a server remotely, and is basically running right after the OS installation, but the default settings are somewhat insecure.
In this section, we will configure the settings to change the default settings and increase the security of the ssh connection.
1.1 Change the configuration file of SSH service.
The configuration file for the SSH service is "/etc/ssh/sshd_config". Open the configuration file with vi editor
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# vi /etc/ssh/sshd_config |
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# $OpenBSD: sshd_config,v 1.104 2021/07/02 05:11:21 dtucker 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:/usr/local/sbin:/usr/sbin # 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. # To modify the system-wide sshd configuration, create a *.conf file under # /etc/ssh/sshd_config.d/ which will be automatically included below Include /etc/ssh/sshd_config.d/*.conf # 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 Port 2244 #AddressFamily any ListenAddress 0.0.0.0 #ListenAddress :: #HostKey /etc/ssh/ssh_host_rsa_key #HostKey /etc/ssh/ssh_host_ecdsa_key #HostKey /etc/ssh/ssh_host_ed25519_key # Ciphers and keying #RekeyLimit default none # Logging #SyslogFacility AUTH #LogLevel INFO # Authentication: #LoginGraceTime 2m PermitRootLogin prohibit-password #StrictModes yes #MaxAuthTries 6 #MaxSessions 10 |
Line 21 "Port 22" This time change to "Port 2244" and proceed
Delete the "#" in line 24 "#ListenAddress 0.0.0.0
Line 41, "#PermitRootLogin prohibit-password", delete "#".
The root user can log in to the server with administrator privileges if the user name is already known and the password is known, so the settings are set to deny this.
Restart SSH
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# systemctl restart sshd.service |
2.How to set up a firewall (firewalld)
In MiracleLinux, the firewall is set to firewalld by default, which is enabled when the OS is installed.
To briefly explain firewalld, when setting up a communication control policy, communication permission/blocking rules are applied to predefined zones, and the zones are assigned to each NIC (network adapter).
2.1 How to use the firewall-cmd command to control "firewalld".
1)Command to check the status and settings of firewalld
①Check firewalld operation status
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# firewall-cmd --state running If "firewalld" is running, "running" will be displayed; if it is not running, "not running" will be displayed. |
OR
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# systemctl status firewalld ● firewalld.service - firewalld - dynamic firewall daemon Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor> Active: active (running) since Tue 2022-11-15 10:33:50 JST; 10min ago Docs: man:firewalld(1) Main PID: 840 (firewalld) Tasks: 2 (limit: 10938) Memory: 41.3M CPU: 575ms CGroup: /system.slice/firewalld.service mq840 /usr/bin/python3 -s /usr/sbin/firewalld --nofork --nopid Nov 15 10:33:42 Lepard systemd[1]: Starting firewalld - dynamic firewall daemon> Nov 15 10:33:50 Lepard systemd[1]: Started firewalld - dynamic firewall daemon. |
Active:The message "inactive (dead)" is displayed, indicating that firewalld is stopped
➁Show default zone settings
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# firewall-cmd --list-all public (active) target: default icmp-block-inversion: no interfaces: ens160 sources: services: cockpit dhcpv6-client ssh ports: protocols: forward: no masquerade: no forward-ports: source-ports: icmp-blocks: rich rules: |
③About the "--permanent" option
In order to prevent the settings from being lost when the server is restarted or the "firewalld" service is restarted, use the "--permanent" option.
If the "--permanent" option is specified, the configuration will not be reflected in "firewalld" as it is, so it is necessary to reflect the configuration using "fiewall-cmd --reload".
As an example, to use the HTTP service permanently without being initialized even if the system is rebooted
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# firewall-cmd --add-service=http --permanent # firewall-cmd --reload |
④How to start and stop
Since firewalld is controlled by systemd, use the systemctl command to start and stop it.
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Start firewalld # systemctl start firewalld Stop firewalld # systemctl stop firewalld |
2.2 Allow modified SSH port 2244
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# firewall-cmd --add-port=2244/tcp --permanent # firewall-cmd --reload # firewall-cmd --list-all public (active) target: default icmp-block-inversion: no interfaces: ens160 sources: services: cockpit dhcpv6-client ssh ports: 2244/tcp protocols: forward: no masquerade: no forward-ports: source-ports: icmp-blocks: rich rules: |
3.Connect remotely from Windows
Setting up in Windows
Use "Tera Term" as a terminal emulator.
Start Tera Term, cancel the startup screen, and then select "New Connection" from "File" in the Tera Term menu.
Enter your own settings in the "Server IP Address" and "TCP Port Number" fields.。Finally, click "OK".
After clicking "OK," click "Continue" on the security confirmation screen.
Enter "User name" and "Passphrase" and click "OK" on the next screen.
If the information is correct, you should be able to log in normally as shown below.
4.NTP Server Settings
Build an NTP server to synchronize the server time with Japan Standard Time
①Chrony Installation and Configuration
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# dnf -y install chrony |
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# vi /etc/chrony.conf Line 3 : comment out and add under it #pool 2.cloudlinux.pool.ntp.org iburst pool ntp.nict.jp iburst |
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# systemctl enable chronyd.service # systemctl restart chronyd.service |
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# firewall-cmd --add-service=ntp --permanent # firewall-cmd --reload |
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# chronyc sources MS Name/IP address Stratum Poll Reach LastRx Last sample ============================================================== ^+ ntp-b2.nict.go.jp 1 6 77 27 -50us[ -342us] +/- 5432us ^+ ntp-b3.nict.go.jp 1 6 77 26 +103us[ +103us] +/- 5681us ^* ntp-k1.nict.jp 1 6 77 26 -250us[ -544us] +/- 3445us ^+ ntp-a2.nict.go.jp 1 6 77 27 -211us[ -503us] +/- 5513us |
If you can see the "*" mark, synchronization is complete.