檢查 SELinux 設定，預設啟用

[doraemon@centos8-gui ~]$ getenforce
Enforcing
[doraemon@centos8-gui ~]$ cat /etc/selinux/config

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=enforcing
# SELINUXTYPE= can take one of these three values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

檢查防火牆設定，預設啟用，預設允許的服務有 ssh、dhcp-client、cockpit

[doraemon@centos8-gui ~]$ sudo systemctl status firewalld
[sudo] password for doraemon:
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset>
   Active: active (running) since Sun 2019-09-29 14:45:38 CST; 28min ago
     Docs: man:firewalld(1)
 Main PID: 984 (firewalld)
    Tasks: 2 (limit: 23858)
   Memory: 34.2M
   CGroup: /system.slice/firewalld.service
           └─984 /usr/libexec/platform-python -s /usr/sbin/firewalld --nofork --nopid

 9月 29 14:45:37 centos8-gui.lab.example.com systemd[1]: Starting firewalld - dynami>
 9月 29 14:45:38 centos8-gui.lab.example.com systemd[1]: Started firewalld - dynamic>

[doraemon@centos8-gui ~]$ sudo firewall-cmd --list-all
public (active)
  target: default
  icmp-block-inversion: no
  interfaces: ens160
  sources:
  services: cockpit dhcpv6-client ssh
  ports:
  protocols:
  masquerade: no
  forward-ports:
  source-ports:
  icmp-blocks:
  rich rules:

看到防火牆已經允許了 cockpit 服務了，那看一下此服務目前的執行狀態如何？

[doraemon@centos8-gui ~]$ sudo systemctl status cockpit.socket
● cockpit.socket - Cockpit Web Service Socket
   Loaded: loaded (/usr/lib/systemd/system/cockpit.socket; disabled; vendor preset: disabled)
   Active: inactive (dead)
     Docs: man:cockpit-ws(8)
   Listen: [::]:9090 (Stream)

代表我們只要對 cockpit.socket 立即啟用，即可使用。

[doraemon@centos8-gui ~]$ sudo systemctl enable --now cockpit.socket
Created symlink /etc/systemd/system/sockets.target.wants/cockpit.socket → /usr/lib/systemd/system/cockpit.socket.
[doraemon@centos8-gui ~]$ sudo systemctl status cockpit.socket
● cockpit.socket - Cockpit Web Service Socket
   Loaded: loaded (/usr/lib/systemd/system/cockpit.socket; enabled; vendor preset: disabled)
   Active: active (listening) since Sun 2019-09-29 15:43:36 CST; 6s ago
     Docs: man:cockpit-ws(8)
   Listen: [::]:9090 (Stream)
  Process: 32380 ExecStartPost=/bin/ln -snf active.motd /run/cockpit/motd (code=exited, status=0/SUCCESS)
  Process: 32371 ExecStartPost=/usr/share/cockpit/motd/update-motd  localhost (code=exited, status=0/SUCCESS)
    Tasks: 0 (limit: 23858)
   Memory: 1.2M
   CGroup: /system.slice/cockpit.socket

 9月 29 15:43:36 centos8-gui.lab.example.com systemd[1]: Starting Cockpit Web Service Socket.
 9月 29 15:43:36 centos8-gui.lab.example.com systemd[1]: Listening on Cockpit Web Service Socket.

輸入帳號密碼，按下登入

即可用圖形的方式看到主機概況

接下來繼續透過 yum repolist 來看看內建有哪些軟體庫可以使用

[doraemon@centos8-gui ~]$ yum repolist
上次中介資料過期檢查：0:42:49 以前，時間點為 西元2019年09月29日 (週日) 15時08分13秒。
軟體庫 ID                                         軟體庫名稱                                                    狀態
AppStream                                         CentOS-8 - AppStream                                          4,928
BaseOS                                            CentOS-8 - Base                                               2,713
extras                                            CentOS-8 - Extras                                                 3

看看有哪些模組可供安裝

[doraemon@centos8-gui ~]$ yum module list
上次中介資料過期檢查：0:44:26 以前，時間點為 西元2019年09月29日 (週日) 15時08分13秒。
CentOS-8 - AppStream
Name                 Stream       Profiles                    Summary
389-ds               1.4                                      389 Directory Server (base)
ant                  1.10 [d]     common [d]                  Java build tool
container-tools      1.0          common [d]                  Common tools and dependencies for container runtimes
container-tools      rhel8 [d][e] common [d]                  Common tools and dependencies for container runtimes
freeradius           3.0 [d]      server [d]                  High-performance and highly configurable free RADIUS se
                                                              rver
gimp                 2.8 [d]      common [d], devel           gimp module
go-toolset           rhel8 [d]    common [d]                  Go
httpd                2.4 [d]      common [d], devel, minimal  Apache HTTP Server
idm                  DL1          common [d], adtrust, client The Red Hat Enterprise Linux Identity Management system
                                  , dns, server                module
idm                  client [d]   common [d]                  RHEL IdM long term support client module
inkscape             0.92.3 [d]   common [d]                  Vector-based drawing program using SVG
javapackages-runtime 201801 [d]   common [d]                  Basic runtime utilities to support Java applications
libselinux-python    2.8          common                      Python 2 bindings for libselinux
llvm-toolset         rhel8 [d][e] common [d]                  LLVM
mailman              2.1 [d]      common [d]                  Electronic mail discussion and e-newsletter lists manag
                                                              ing software
mariadb              10.3 [d]     client, server [d], galera  MariaDB Module
maven                3.5 [d]      common [d]                  Java project management and project comprehension tool
mercurial            4.8 [d]      common [d]                  Mercurial -- a distributed SCM
mod_auth_openidc     2.3                                      Apache module suporting OpenID Connect authentication
mysql                8.0 [d]      client, server [d]          MySQL Module
nginx                1.14 [d]     common [d]                  nginx webserver
nodejs               10 [d]       common [d], development, mi Javascript runtime
                                  nimal, s2i
parfait              0.5          common                      Parfait Module
perl                 5.24         common [d], minimal         Practical Extraction and Report Language
perl                 5.26 [d]     common [d], minimal         Practical Extraction and Report Language
perl-App-cpanminus   1.7044 [d]   common [d]                  Get, unpack, build and install CPAN modules
perl-DBD-MySQL       4.046 [d]    common [d]                  A MySQL interface for Perl
perl-DBD-Pg          3.7 [d]      common [d]                  A PostgreSQL interface for Perl
perl-DBD-SQLite      1.58 [d][e]  common [d]                  SQLite DBI driver
perl-DBI             1.641 [d][e] common [d]                  A database access API for Perl
perl-FCGI            0.78 [d]     common [d]                  FastCGI Perl bindings
perl-YAML            1.24 [d]     common [d]                  Perl parser for YAML
php                  7.2 [d]      common [d], devel, minimal  PHP scripting language
pki-core             10.6                                     PKI Core
pki-deps             10.6                                     PKI Dependencies
postgresql           10 [d]       client, server [d]          PostgreSQL server and client module
postgresql           9.6          client, server [d]          PostgreSQL server and client module
python27             2.7 [d]      common [d]                  Python programming language, version 2.7
python36             3.6 [d][e]   common [d], build           Python programming language, version 3.6
redis                5 [d]        common [d]                  Redis persistent key-value database
rhn-tools            1.0 [d]      common [d]                  Red Hat Satellite 5 tools for RHEL
ruby                 2.5 [d]      common [d]                  An interpreter of object-oriented scripting language
rust-toolset         rhel8 [d]    common [d]                  Rust
satellite-5-client   1.0 [d][e]   common [d], gui             Red Hat Satellite 5 client packages
scala                2.10 [d]     common [d]                  A hybrid functional/object-oriented language for the JV
                                                              M
squid                4 [d]        common [d]                  Squid - Optimising Web Delivery
subversion           1.10 [d]     common [d], server          Apache Subversion
swig                 3.0 [d]      common [d], complete        Connects C/C++/Objective C to some high-level programmi
                                                              ng languages
varnish              6 [d]        common [d]                  Varnish HTTP cache
virt                 rhel [d][e]  common [d]                  Virtualization module

Hint: [d]efault, [e]nabled, [x]disabled, [i]nstalled

由此得知，透過內建的軟體庫，可以安裝 Apache (httpd) 2.4、MariaDB 10.3、MySQL 8.0、PHP 7.2。

來跑一下更新吧！

[doraemon@centos8-gui ~]$ sudo yum check-update
[doraemon@centos8-gui ~]$ sudo yum update -y
[sudo] password for doraemon:
上次中介資料過期檢查：0:07:45 以前，時間點為 西元2019年09月29日 (週日) 15時59分26秒。
依賴關係解析完畢。
無事可做。
完成！
[doraemon@centos8-gui ~]$ sudo systemctl reboot