{"id":11748,"date":"2019-03-16T04:31:01","date_gmt":"2019-03-16T04:31:01","guid":{"rendered":"http:\/\/www.appservgrid.com\/paw92\/?p=11748"},"modified":"2019-03-16T04:31:01","modified_gmt":"2019-03-16T04:31:01","slug":"initial-server-setup-and-configurations-on-centos-7","status":"publish","type":"post","link":"https:\/\/www.appservgrid.com\/paw92\/index.php\/2019\/03\/16\/initial-server-setup-and-configurations-on-centos-7\/","title":{"rendered":"Initial Server Setup and Configurations on CentOS 7"},"content":{"rendered":"

This tutorial will explain the first basic steps you need to go through after installing a minimal\u00a0CentOS 7<\/strong>\u00a0system with no graphical environment in order to obtain information about the installed system, the hardware on top of which runs the system and configure other specific system tasks, such as networking, root privileges, software, services and others.<\/p>\n

Requirements<\/h4>\n
    \n
  1. CentOS 7 Minimal Installation<\/a><\/li>\n<\/ol>\n

    Important<\/strong>: RHEL 7 users, can follow this article to do a\u00a0Initial Server Setup on RHEL 7<\/a>.<\/p>\n

    Update CentOS 7 System<\/h3>\n

    The first step you need to perform on a fresh installed CentOS system is to make sure the system is up-to-date with the latest kernel and system security patches, software repositories and packages.<\/p>\n

    To fully update a\u00a0CentOS 7<\/strong>\u00a0system, issue the following commands with root privileges.<\/p>\n

    # yum check-update\r\n# yum upgrade<\/pre>\n
    After the upgrade process completes, in order to release disk space you can remove all downloaded packages that where used in the process of upgrading alongside with all cached repositories information by executing the following command.<\/p>\n
    # yum clean all\r\n<\/pre>\n
    \n
    \"Yum<\/a><\/p>\n
    Yum Clean All on CentOS 7<\/p>\n<\/div>\n
    Install System Utilities on CentOS 7<\/h3>\n
    The following utilities packages can prove to be useful for day-by-day system administration:\u00a0nano<\/strong>\u00a0(text editor to replace\u00a0vi editor<\/a>),\u00a0wget<\/a>,\u00a0curl<\/strong>\u00a0(utilities used for downloading packages over network mostly)\u00a0net-tools<\/strong>,\u00a0lsof<\/a>(utilities for managing local networking) and bash-completion (command line autocomplete).<\/p>\n
    Install them all in one-shot by executing the below command.<\/p>\n
    # yum install nano wget curl net-tools lsof bash-completion\r\n<\/pre>\n
    \n
    \"Install<\/a><\/p>\n
    Install System Utilities<\/p>\n<\/div>\n
    Setup Networking in CentOS 7<\/h3>\n
    CentOS 7<\/strong>\u00a0has a wide range of tools that can be used to configure and manage networking, from manually editing the network configuration file to using commands such as\u00a0ip<\/a>,\u00a0ifconfig<\/a>,\u00a0nmtui<\/strong>,\u00a0nmcli<\/a>\u00a0or\u00a0route<\/strong>.<\/p>\n
    The easiest utility a beginner can use to manage and change network configurations is\u00a0nmtui<\/strong>\u00a0graphical command line.<\/p>\n
    In order to change the system hostname via\u00a0nmtui<\/strong>\u00a0utility, execute\u00a0nmtui-hostname<\/strong>\u00a0command, set your machine hostname and press\u00a0OK<\/strong>\u00a0to finish, as illustrated in the below screenshot.<\/p>\n
    # nmtui-hostname\r\n<\/pre>\n
    \n
    \"Set<\/a><\/p>\n
    Set Hostname in CentOS 7<\/p>\n<\/div>\n
    To manipulate a network interface, execute\u00a0nmtui-edit<\/strong>\u00a0command, choose the interface you want to edit and select\u00a0edit<\/strong>\u00a0from the right menu, as shown in the below screenshot.<\/p>\n
    # nmtui-edit\r\n<\/pre>\n
    \n
    \"Configure<\/a><\/p>\n
    Configure Network in CentOS 7<\/p>\n<\/div>\n
    Once you\u2019re in the graphical interface provided by\u00a0nmtui<\/strong>\u00a0utility you can setup the network interface IP settings as illustrated in the below screenshot. When you finish, navigate to\u00a0OK<\/strong>\u00a0using\u00a0[tab]<\/strong>\u00a0key to save the configuration and quit.<\/p>\n
    \n
    \"Setup<\/a><\/p>\n
    Setup Network IP Address<\/p>\n<\/div>\n
    In order to apply the network interface new configuration, execute\u00a0nmtui-connect<\/strong>\u00a0command, select the interface you want to manage and hit on\u00a0Deactivate\/Activate<\/strong>\u00a0option to decommission and rise-up the interface with the IP settings, as presented in the below screenshots.<\/p>\n
    # nmtui-connect\r\n<\/pre>\n
    \n
    \"Active<\/a><\/p>\n
    Active Network Interface<\/p>\n<\/div>\n
    In order to view the network interface settings, you can inspect the content of the interface file or you can issue the below commands.<\/p>\n
    # ifconfig enp0s3\r\n# ip a\r\n# ping -c2 google.com\r\n<\/pre>\n
    \n
    \"Verify<\/a><\/p>\n
    Verify Network Configuration<\/p>\n<\/div>\n
    Other useful utilities that can be used to manage speed, link state or obtain information about machine network interfaces are\u00a0ethtool<\/strong>\u00a0and\u00a0mii-tool<\/strong>.<\/p>\n
    # ethtool enp0s3\r\n# mii-tool enp0s3\r\n<\/pre>\n
    \n
    \"Check<\/a><\/p>\n
    Check Network Connection<\/p>\n<\/div>\n
    An important aspect of your machine networking is to list all open network sockets in order to see what programs are listening on what ports and what\u2019s the state of the established network connections.<\/p>\n
    To list all servers that have opened\u00a0TCP<\/strong>\u00a0or\u00a0UDP<\/strong>\u00a0sockets in listening state issue the following commands. However,\u00a0UDP<\/strong>\u00a0server won\u2019t list any socket state due to the fact that UDP is a connectionless protocol which only sends packets over network and doesn\u2019t establish connections.<\/p>\n
    # netstat -tulpn\r\n# ss -tulpn\r\n# lsof -i4 -6\r\n<\/pre>\n
    Manage Services in CentOS 7<\/h3>\n
    CentOS 7<\/strong>\u00a0manages daemons or service via\u00a0systemctl utility<\/a>. In order to list all services state, issue the following command.<\/p>\n
    # systemctl list-units\r\n<\/pre>\n
    \n
    \"List<\/a><\/p>\n
    List All Services State<\/p>\n<\/div>\n
    To check if a daemon or service is enabled to automatically start when the system starts, issue the following command.<\/p>\n
    # systemctl list-unit-files -t service\r\n<\/pre>\n
    \n
    \"List<\/a><\/p>\n
    List Enabled Services<\/p>\n<\/div>\n
    To list the old\u00a0SysV<\/strong>\u00a0services present in your system and disable them issue the following\u00a0chkconfig commands<\/a>.<\/p>\n
    # chkconfig --list\r\n# chkconfig service_name off\r\n<\/pre>\n
    5. Disable Unwanted Services in CentOS 7<\/h3>\n
    It\u2019s recommended after installing\u00a0CentOS 7<\/strong>, to list what services are running in the system by running the above commands and disable and remove them in order to reduce the attacks vectors against your system.<\/p>\n
    For instance,\u00a0Postfix<\/strong>\u00a0daemon is installed and enabled by default in CentOS 7. If your system don\u2019t require running a mail server, it\u2019s best to stop, disable and remove the postfix service by issuing the below commands.<\/p>\n
    # systemctl stop postfix\r\n# systemctl disable postfix\r\n# yum remove postfix\r\n<\/pre>\n
    In addition to\u00a0netstat<\/a>,\u00a0ss<\/strong>,\u00a0lsof<\/a>\u00a0or\u00a0systemctl<\/a>\u00a0commands, you can also run\u00a0ps<\/a>,\u00a0top<\/a>\u00a0or\u00a0pstree<\/strong>\u00a0commands in order to discover and identify what unwanted services are running in your system and disable or remove them.<\/p>\n
    By default,\u00a0pstree<\/strong>\u00a0utility is not installed in CentOS 7. To install it execute the following command.<\/p>\n
    # yum install psmisc\r\n# pstree -p\r\n<\/pre>\n
    \n
    \"List<\/a><\/p>\n
    List Linux Processes in Tree Format<\/p>\n<\/div>\n
    Enable Firewall in CentOs 7<\/h3>\n
    Firewalld<\/a>\u00a0is the main firewall utility that uses interacts with in order to manage iptables rules.
    \nTo enable and start and verify the firewall in CentOS 7, execute the following commands.<\/p>\n
    # systemctl enable firewalld\r\n# systemctl start firewalld\r\n# systemctl status firewalld\r\n<\/pre>\n
    In order to open a specific service to incoming connections, first verify if the application is already present in\u00a0firewalld<\/strong>\u00a0rules and, then, add the rule for the service, as shown in the below example which allows\u00a0SSH<\/strong>incoming connections. Use\u00a0--permanent<\/code>\u00a0switch to add the rule permanently.<\/p>\n
    # firewall-cmd --add-service=[tab]  #List services\r\n# firewall-cmd --add-service=ssh\r\n# firewall-cmd --add-service=ssh --permanent\r\n<\/pre>\n
    \n
    \"Open<\/a><\/p>\n
    Open Service in Firewalld<\/p>\n<\/div>\n
    In case the service is now already defined in firewalld rules, you can manually add the service port, as shown in the below example.<\/p>\n
    # firewall-cmd --add-port=22\/tcp --permanent\r\n# firewall-cmd --reload     #Apply the rule on-fly\r\n<\/pre>\n
    Enable Sudo Permissions on User Accounts<\/h3>\n
    In order to grant root permissions for a normal user, first create the user by issuing\u00a0adduser command<\/a>, set the password for the user and grant root permissions to the user by executing the below command which adds the new user to the administrative wheel group.<\/p>\n
    # adduser tecmint\r\n# passwd tecmint\r\n# usermod -aG wheel tecmint\r\n<\/pre>\n
    To test if the new user has root privileges, login to the system with user\u2019s credentials and run yum command with sudo permissions, as shown in the below excerpt.<\/p>\n
    # su - tecmint\r\n# sudo yum update\r\n<\/pre>\n
    \n
    \"Verify<\/a><\/p>\n
    Verify Sudo User Permissions<\/p>\n<\/div>\n
    Configure SSH Public Key Authentication on CentOS 7<\/h3>\n
    In order to secure SSH your server and set up public key authentication to increase the security of your server with a private SSH key to log in, first generate a SSH Key Pair with a following command.<\/p>\n
    Don\u2019t not enter a passphrase in case you want to automate server management via SSH.<\/p>\n
    # ssh-keygen -t RSA\r\n<\/pre>\n
    After the SSH key pairs had been generated, copy the key to the server you want to connect to by issuing the below command. Initially, enter you remote SSH user password in order to copy the public key.<\/p>\n
    # ssh-copy-id remote_user@SSH_SERVER_IP\r\n<\/pre>\n
    After the SSH public key has been copied to the remote server, login to the remote SSH server with the following command.<\/p>\n
    # ssh remote_user@SSH_SERVER_IP\r\n<\/pre>\n
    Finally, in order to secure the SSH server, make sure you disallow remote SSH access to the root account by opening the configuration SSH file\u00a0\/etc\/ssh\/sshd_config<\/strong>\u00a0with your text editor as root and change it from\u00a0Yes<\/code>\u00a0to\u00a0No<\/code>.<\/p>\n
    PermitRootLogin no\r\n<\/pre>\n
    To apply the setting you need to restart the SSH service so that it will use the new configuration.<\/p>\n
    # systemctl restart sshd\r\n<\/pre>\n
    That\u2019s all! These are just a few basic settings and commands every system administrator needs to know and apply on a fresh installed CentOS system or in order to perform day to day tasks on the system.<\/p>\n
    To secure and harden CentOS 7 server, check out these following articles.<\/p>\n
      \n
    1. The Mega Guide To Harden and Secure CentOS 7 \u2013 Part 1<\/a><\/li>\n
    2. The Mega Guide To Harden and Secure CentOS 7 \u2013 Part 2<\/a><\/li>\n<\/ol>\n
      If you\u2019re planning to deploy websites on this CentOS 7 system, learn how to setup and configure\u00a0LAMP stack<\/a>\u00a0or\u00a0LEMP stack<\/a>.<\/p>\n
      Source<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
      This tutorial will explain the first basic steps you need to go through after installing a minimal\u00a0CentOS 7\u00a0system with no graphical environment in order to obtain information about the installed system, the hardware on top of which runs the system and configure other specific system tasks, such as networking, root privileges, software, services and others. … <\/p>\n
      Continue reading “Initial Server Setup and Configurations on CentOS 7”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-11748","post","type-post","status-publish","format-standard","hentry","category-linux"],"_links":{"self":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/11748","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/comments?post=11748"}],"version-history":[{"count":1,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/11748\/revisions"}],"predecessor-version":[{"id":11749,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/11748\/revisions\/11749"}],"wp:attachment":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/media?parent=11748"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/categories?post=11748"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/tags?post=11748"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}