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OS 7 minimal installation for servers comes with some default pre installed services, such as Postfix Mail Transfer Agent daemon, Avahi mdns daemon multicast Domain Name System and Chrony service, which is responsible to maintain system clock. Remove Services in Cent. OS 7. Now comes to the question. Why wed need to disable all these services. One of the main reason would be to increase system security level degree, the second reason is system final destination and the third is system resources. Requirements. Cent. OS 7 Minimal Installation. RHEL 7 Minimal Installation. If you are planning to use your newly installed RHELCent. OS 7 to host, lets say, a small website which runs on Apache or Nginx, or to provide network services like DNS, DHCP, PXE boot, FTP server, etc or other services that dont require to run Postifx MTA daemon, Chrony or Avahi daemon, then why we should keep all these unnecessary daemons installed or even running on your server. The main external services that your server truly requires to run after you perform a minimal installation would be just a SSH daemon, in order to allow remote logins on system, and, in some cases, NTP service, to accurately synchronize your server internal clock with external NTP servers. DisableRemove Postfix MTA, Avahi and Chrony Services. After the installation finishes, login on your server with root account or a user with root privileges and perform a system update, to make sure that your system is up to date with all packages and security patches. Upgrade System. 2. The next step would be to install some useful system utilities using YUM Package Manager, such as net tools this package provides the olderbut good ifconfig command, nano text editor, wget and curl for URL transfers, lsof to list your open files and bash completion, which auto completes typed commands. Install System Utilities. Now you can start disabling and remove pre installed unwanted services. First of all get a list of all your enabled and running services by running netstat command against TCP, UDP and Listen state network sockets. For Delphi 7. To output numerical service sockets. To output literal service sockets. List Enabled Services. As you can see Postfix is started and listens on localhost on port 2. Avahi daemon binds on all network Interfaces and Chronyd service binds on localhost and all network interfaces on different ports. Proceed with Postfix MTA service removal by issuing the following commands. Remove Postfix Service. Next remove Chronyd service, which will be replaced by NTP server, by issuing the following commands. Remove Chronyd Service. Now its time to remove Avahi daemon. Looks like in RHELCent. OS 7 Avahi daemon is strongly tight and depends on Network Manager service. Performing Avahi daemon removal can leave your system without any network connections. So, pay extra attention to this step. If you really need automatic network configuration provided by Network Manager or you need to edit your interfacesthrough nmtui network and interface utility, then you should only stop and disable Avahi daemon and perform no removal at all. If you still want to completely remove this service then you must manually edit network configuration files located in etcsysconfignetwork scriptsifcfg interfacename, then start and enable networking service. Issue the following commands to remove Avahi mdns daemon. Caution Do not attempt to remove Avahi daemon if you connected through SSH. Stop here if you dont want removal . Remove Avahi Daemon. This step is required only if you removed Avahi daemon and your network connections crashed and you need to manually configure Network Interface Card again. To edit your NIC to use IPv. IP Address, go to etcsysconfignetwork scripts path, open NIC interface file usually the first card is named ifcfg eno. Network Manager and use the following excerpt as a guide in case yournetwork interface has no configuration. IPV6. INITno. IPV6AUTOCONFyes. DEVICEeno. 16. 77. UUIDc. 3f. 0dc. 21 d. IPV4FAILUREFATALno. IPV6DEFROUTEno. IPV6FAILUREFATALno. NAMESystem eno. IPV6PEERDNSyes. IPV6PEERROUTESyes. HWADDR0. 0 0. C 2. E2 0. 6 E9. IPADDR1. NETMASK2. 55. 2. GATEWAY1. DNS11. 92. 1. 68. Configure Network Interface. The most important settings here you should take into consideration are BOOTPROTO Set to none or static for static IP Address. ONBOOT Set to yes to bring up your interface after reboot. DEFROUTE Statement commented with a or completely removed do not use default route If you use it here you should add DEFROUTE no to all network interfaces, not used as the default route. If your infrastructure has an DHCP Server that automatically assigns IP Addresses, use the following excerpt for Network Interfaces Configuration. IPV6. INITno. IPV6AUTOCONFyes. DEVICEeno. 16. 77. UUIDc. 3f. 0dc. 21 d. IPV4FAILUREFATALno. IPV6DEFROUTEno. IPV6FAILUREFATALno. NAMESystem eno. IPV6PEERDNSyes. IPV6PEERROUTESyes. HWADDR0. 0 0. C 2. E2 0. 6 E9. Configure DHCP Interface. Same as the configuration with Static IP Address, assure that BOOTPROTO is set to dhcp, DEFROUTE statement is commented or removed and the device is configured to automatically start on boot. If you dont use IPv. IPV6. 9. In order to apply the new configurations for your network interfaces you must restart network service. After you restart network daemon use ifconfigor ip addr show command to get your interface settings and try to ping a domain name to see if network is functional. Use this command before systemctl. Confirm Network Settings. As a final setting make sure you set up a name for system hostname using hostnamectl utility and review your configuration with hostname command. FQDNsystemname. Short name. FQDN name. Setup System Hostname. Thats all As a final test run netstat command again to get a look of what services are running on your system. Verify Running Services. Besides SSH server, if your network uses DHCP to pull dynamic IP configurations, a DHCP Client should run and be active on UDP ports. Verify DHCP Service. As an alternative to netstat utility you can output your running network sockets with the help of Sockets Statistics command. Command to Check Network. Reboot your server and run systemd analize command to determine your system boot up time performance and, also, use free and Disk. Free command to display RAM and HDD statistics and top command to see a top of the most used system resources. Check System Boot Time. Check Memory and Disk Usage. Congratulations Now you have a clean minimal RHELCent. OS 7 system environment with less services installed and running and more resources available for future configurations. Read Also Stop and Disable Unwanted Services from Linux.