Red Hat RHCSARHCE 7 Cert Guide（三）

zhangleivod

1.console and terminal
        A console is basically what you see when you are looking at your computer screen
        A terminal is an environment that is opened on the console, and which provides
                access to a text shell, which is the command-line environment that can be used to
                type commands
2.pts:除了在桌面使用CTRL+ALT+Fn打开的终端（open a terminal）
  tty:在桌面使用CTRL+ALT+F1打开的终端
  in the graphical environment, you need to use Ctrl+Alt+Fn key instead
  in the tty ,you need to use Alt+Fn
3.Alt+F1 through Alt+F6 .(chvt 1(6))
4.The systemd process is the first process that was started when the server was started
5.
        sytemctl reboot (reboot)
        systemctl halt(halt)
        systemctl poweroff(poweroff)
        echo b > /proc/sysrq-trigger #force a machine to reset(Notice that this command should be used only if there are no other options!)
6.sshd service must be running and offering services at port 22
        ssh -p followed by the port number you want to connect to.
        ssh remoteserver -l root(ssh root@remoteserver)
        ssh -p 22 192.168.101.111
        ssh 192.168.101.111 -l root
        systemctl status sshd #This should show you that the sshd process is currently up and running.
        systemctl stop firewalld
        ip a |grep 'inet'
        ssh -v: This will start SSH in verbose mode and show all the individual components that are contacted.
7.After connecting to the remote server, a public key fingerprint is stored in the file ~/.ssh/known_hosts.
8./etc/ssh/ssh_config :ForwardX11 yes
        The next time you use the ssh command, X forwarding will be available by default.
9.scp
        scp /etc/hosts server2:/tmp
        scp root@server2:/etc/passwd ~
        scp -r server2:/etc/ /tmp
        scp -P: the port number you want to connect to
        ssh -p(lowercase):the port number you want to connect to
10.rsync
11.The public key(~/.ssh/known_hosts) is stored in the home directory of the target user on the SSH server.
12.Connecting to a Remote Server with Public/Private Keys
        ssh-keggen
        ssh-copy-id server2
13.yum install -y screen
        screen
        (Ctrl+a, d )key sequence to detach from the screen session and log out from the SSH session.
        screen -r(Attach to the screen session again using screen -r)
        Ctrl+a, ? . This shows a list of all commands that are available
        Ctrl+a, / , which will close the screen session
        Make sure to remove screen sessions that you do not need anymore, otherwise they will stay
                active until the next time you reboot your server!
        To find out which screen sessions currently are running, use the screen -ls
        The second user can just connect to the screen session, using screen -x
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1.To get information about a user account, you can use the id command.
        id linda
2.
        su Opens a subshell as a different user, with the advantage that only in the subshell commands are executed as root
        sudo Allows you to set up an environment where specific tasks are executed with administrative privileges
        su:If you need complete access to the entire environment of the target user account, you can use su - to start a login shell.
        sudo:This is definitely more secure because you will only be able to act as if you have administrator permissions while running this specific command.
3.sudo:
        1. Make the administrative user account member of the group wheel by using
                usermod -aG wheel user .
        2. Type visudo and make sure the line %wheel ALL=(ALL) ALL is included.
4.pkexec and polkit
5./etc/passwd and /etc/shadow