Linux¶

With the same Linux Kernel, there are different distributions of Linux based on different modes of software management, such as CentOS based on RPM and Ubuntu on DPKG.

Installation¶

Download and install CentOS ISO. Without a server, VMware is an option where to install the system.

Remote Connection¶

If the system needs to be connected to remotely, XShell is a fine tool and SSH which is commonly configured on the Linux is required. Check with service sshd status. If not, execute following commands in order:

yum install openssh-server installs SSH
vim /etc/ssh/ssh_config edits the configuration file
/bin/systemctl start sshd.service starts SSH service
/bin/systemctl enable sshd.service starts the service at startup.

Most remote connections like MySQL and Redis support connection through SSH. In this case, AllowTcpForwarding yes is required to set in the /etc/ssh/sshd_config.

Mirror¶

Change mirror to aliyun:

base: wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
epel: wget -O /etc/yum.repos.d/epel-7.repo http://mirrors.aliyun.com/repo/epel-7.repo

Execute yum clean all to update mirrors and yum makecache to create caches.

Directory¶

Directories of RPM are commonly set as following by default:

/etc: configuration files
/usr/bin: executable files
/usr/lib: dynamic libraries
/usr/share/doc: use documentations
/usr/share/man: man page files

Get Started¶

Linux is a multi-user system with limits of authority. Use su command to access system as root when logging in as a common user and exit to get back.

Development Tools¶

Install common development tools.

yum -y groupinstall "Development tools"
yum install -y bash-completion vim lrzsz wget expect net-tools nc nmap tree dos2unix htop iftop iotop unzip telnet sl psmisc nethogs glances bc

System and Partitions¶

Each hardware device in Linux is regarded as a file. They are almost all under /dev directory.

Service¶

Relative commands are shown as follows:

/bin/systemctl start <service>
service <service> status
/bin/systemctl enable <service> # start at startup

User and Privilege¶

id show ids
useradd add a new user
passwd [username] change password for users

Files and Directories Management¶

Path¶

Absolute paths start with the root path /, such as /usr/share/doc. But on the contrary, relative paths don't start with /, share/etc for example.

Commands¶

Use -help to list some options of the command or use man/info commands to show details, such as man cd. Following are some common commands.

Directory¶

cd change directory
pwd print working directory
mkdir make a directory by a level. Append -p after the command if recursion is required.
rmdir remove an empty directory by a level. Append -p if recursion is required.

Operator¶

ls list
cp copy
rm remove
mv move

Text Document¶

cat concatenate content of file
tac concatenate content in reverse direction
nl print with line numbers
more print one page. Click Space to next page or Enter to next line.
less familiar to more
head defaults to the first 10 lines
tail familiar to head

Upload and Download¶

Install toolkit rz and sz by yum install lrzsz. Then use commands rz to upload or sz to download. Target files will be upload to current directory.

Vim¶

Misc¶

Firewall¶

The service name is firewalld and the command is firewall-cmd.

Open the specific port when remote connections are refused.

firewall-cmd --zone=public --add-port=<port/tcp> [--permanent]

FAQ¶

Pane is dead¶

If it occurs to Pane is dead when installing, open settings of hardwares and then change CD/DVD (IDE) connection to the path of the ISO file.

Connect to Internet¶

If failed, open settings of current network connection of the host and allow Internet Connection Sharing.

Static IP¶

Edit the /etc/sysconfig/network-scripts/ifcfg-ens33 file:

BOOTPROTO="static"
IPADDR=<ip>
NETMASK=255.255.255.0
GATEWAY=<gateway> # same as that of the host
DNS1=<dns1> # also same as those of the host
DNS2=<dns2>

References¶

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