计算机基础教程

整理 google doc：Basics: Linux Basic

# 命令执行本质

一个命令行终端是一个shell进程，在这个终端里执行的程序都是作为该shell进程的子进程。如果子进程命令阻塞终端shell进程，shell进程就会等待子进程退出才能接收其他命令；如果关掉了shell终端，，依附的所有子进程都会退出；加上&号可以避免这种情况，原理是将命令挂在systemd系统守护进程名下，其他办法还有nohup或者开tmux或者screen，并且加&可以让shell进程不再阻塞，从而继续响应新命令；

set -x 可以显示shell在执行什么程序

当使用 sudo 时，系统会使用 /etc/sudoers 这个文件中规定的该用户的权限和环境变量

# 重定向/管道

重定向

输入<+输出流>

exec 8<> /dev/tcp/www.baidu.com/80

重定向到文件：> file

重定向到文件描述符要加&>& fd

echo -e "GET / HTTP/1.0\n" 1>& 8 cat 0<& 8 或 cat<&8
标准输出重定向：

比如标准输出重定向 java -jar **.jar > log.txt

2>&1 标准错误输出重定向到标准输出

如果需要sudo权限，可以用tee：sudo tee
```
cat shopee.sg.domain.uniq | filter-resolved > shopee.sg.domain.uniq.resolved
cat shopee.sg.domain.uniq | filter-resolved | sudo tee shopee.sg.domain.uniq.resolved
```
标准输入重定向：管道|和<<< 以及命令替换$()：

首先$()主要则是command substitution，比如 rm $(where connect.sh)

dos2unix $(find . -type f)

echo $(cmd) 和 echo "$(cmd)"，结果差不多，但是仍然有区别。注意观察，双引号转义完成的结果会自动增加单引号，而前者不会，如果 $ 读取出的参数字符串包含空格，应该用双引号括起来，否则就会出错。

管道：

ps -aef | grep -v grep | grep "java -server -jar" | awk '{print $2}' $(2)获取管道前面等输出结果第二列,此时可以用$2替代；

标准输入重定向符：

<<< String 比如脚本中读取第一个参数并取分隔''的第一个值 IFS='/' read -ra target_arr <<< "$1"
位置参数${}：

${}主要是作为positional parameter，

$｛2｝还可以表示获取脚本输入参数等第二个，此时也可以用$2替代，$#是输入参数个数；
```
$ animal=cat
$ echo $animals
# No such variable as “animals”.
$ echo ${animal}s
cats
```
{}https://askubuntu.com/questions/339015/what-does-mean-in-the-find-command

https://labuladong.gitbook.io/algo/di-wu-zhang-ji-suan-ji-ji-shu/linux-jin-cheng https://labuladong.gitbook.io/algo/di-wu-zhang-ji-suan-ji-ji-shu/linuxshell

difference between ${} and $() in shell script https://superuser.com/questions/935374/difference-between-and-in-shell-scriptcd /proc/$$/fd $$代表当前解释程序
哪些命令接受标准输入

命令默认都接受参数 -argument，有些命令还接受标准输入（可以使用管道符|和重定向符< <<<）, 简单判别方式：命令是否可以阻塞终端（如cat不加任何命令会阻塞终端）如 echo"trade:trade"|chpasswd

# 用户身份和权限

su _gvm
This account is currently not available.

sudo -u _gvm gvmd --migrate
sudo su -l _gvm -s /bin/bash

sudo sh -c "cmds"

Permissions take a different meaning for directories. Here's what they mean:

read determines if a user can view the directory's contents, i.e. do ls in it.
write determines if a user can create new files or delete file in the directory. (Note here that this essentially means that a user with write access toa directory can delete files in the directory even if he/she doesn't have write permissions for the file! So be careful with this.)
execute determines if the user can cd into the directory.

# 安装包管理

# 不同发行版选择

Ubuntu / kali / parrotOS

based on debian,
Centos

for bigdata
Redhat

for databases(because those database companies use redhat, it’s tested)

# 基本安装方法

apt或yum安装

add to apt/yum repository, and then apt-get/yum install ***

Normally will be put in /usr/bin/

Additionally, you can use yum localinstall <packagename> to intelligently install dependencies as needed.

Know the version before installing:

apt policy <packagename>

yum info/search <packagename>
deb或rpm安装

download deb for ubuntu or rpm for centos, and install it, it will help you install all related dependencies
- 版本
  
  amd64, i386,x64 https://askubuntu.com/questions/32402/amd64-i386-32bit-64bit-which-version-to-choose
- 包类型：dpkg(Ubuntu) , rpm(centos)
  
  http://linuxintro.org/index.php?title=Dpkg-rpm_equivalent_commands&redirect=no
  
  deb for debian
```
dpkg -i google-chrome-stable_current_amd64.deb
apt install ./google-chrome-stable_current_amd64.deb
```
  rpm for # CentOS/RHEL
```
rpm -Uvh gitlab-ce-<version>.rpm
如果是第一次安装可以用rpm -ivh gitlab-ce-<version>.rpm
yum localinstall gitlab-ce-<version>.rpm
```
解压直接使用 download tar file, and extract, then:
1. set env variable or persist it in:
e.g. export PATH=$PATH:/usr/local/go/bin

i) 特定用户的PATH ~/bashrc ~/bash_profile

ii) system wide全局PATH /etc/profile或/root/.bashrc

Anything in ~/.profile and ~/.bashrc is run after /etc/profile and /bash.bashrc

所以如果是修改了/etc/profile对root或sudo操作无效，要看下root下面的~/.bashXXX是不是有PATH设置，

如果还不生效，就要看下 Defaults secure_path = /sbin:/bin:/usr/sbin:/usr/bin，可以使用 sudo -E 绕过

For some setups the -E switch will not work. To "workaround" it you can use sudo env "PATH=$PATH" bash. This will also carry your current $PATH forward to your sudo environment.
1. or just mv it into /usr/local/bin/
2. or link
cd /usr/bin sudo ln -s /home/lyhistory/.local/bin/tldr tldr OR

sudo ln -sf /usr/local/share/$PHANTOM_JS/bin/phantomjs /usr/local/bin

缺点: if there is dependencies, you have to manually install them
源码编译安装

configuration或cmake之后make install，通常安装的路径在 install_manifest.txt，所以删除方式：cat install_manifest.txt | xargs echo sudo rm | sh
The steps:
1. The autogen.sh script generates the configure script (from configure.ac, using autoconf) and any files it needs (like creating Makefile.in from Makefile.am using automake). This requires autotools to be installed on your system, and it must be run when checking out the project from source control (if configure isn’t checked in). People who download source tarballs can usually skip this step, because output of this step is included in source tarballs.
  
  Note This is usually equivalent to autoreconf --install. If there is not autogen.sh file, then just run autoreconf --install instead. If you have inherited a project with an autogen.sh, consider deleting it if you can use autoreconf --install.
2. The configure script generates Makefile and other files needed to build. Typically Makefile.in is used as a template to generate Makefile (and config.h.in to generate config.h). This process happens using only standard tools installed on your system, like sed and awk, and doesn't require autotools to be installed.
3. The make command builds the software.
4. The make install command installs it.
https://stackoverflow.com/questions/50044091/what-is-the-job-of-autogen-sh-when-building-a-c-package-on-linux

常见问题：

前面几种安装方法的比较：rpm -ivh -uvh VS yum install vs yum localinstall

[https://serverfault.com/questions/825320/difference-between-rpm-ivh-package-and-yum-install-package#:~:text=there%20is%20no%20difference%20if,works%20with%20file(s).](https://serverfault.com/questions/825320/difference-between-rpm-ivh-package-and-yum-install-package#:~:text=there is no difference if,works with file(s).)
安装后管理
- rpm包安装的，可以用rpm -qa | grep "软件或者包的名字"。
- deb包安装的，可以用dpkg -l | grep "软件或者包的名字"；
- yum方法安装的，可以用yum list installed | grep "软件名或者包名"；
- apt方法安装的，apt list --installed|grep "TEXT"
- 如果是以源码包自己编译安装的，例如.tar.gz或者tar.bz2形式的，这个只能看可执行文件是否存在了，如果是以root用户安装的，可执行程序通常都在/sbin:/usr/bin目录下。
安装后找不到命令，因为安装的位置不在系统path上，可以参考上面的“解压后使用”的方式中的，link或设置环境变量方式来搞；

# apt

apt vs apt-get
apt update
apt upgrade / apt full-upgrade
apt search "PKG"
apt list --installed | grep "PKG"

# yum

yum history
yum history info 21


[[email protected] ~]# yum repolist
Loaded plugins: fastestmirror, langpacks
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
Determining fastest mirrors
 * base: mirror.newmediaexpress.com
 * epel: mirrors.aliyun.com
 * extras: mirror.newmediaexpress.com
 * updates: mirror.newmediaexpress.com
repo id                                                                                   repo name                                                                                                       status

!base/7/x86_64                                                                            CentOS-7 - Base                                                                                                 10,097

!docker-ce-stable/x86_64                                                                  Docker CE Stable - x86_64                                                                                           63

!epel/x86_64                                                                              Extra Packages for Enterprise Linux 7 - x86_64                                                                  13,499

!extras/7/x86_64                                                                          CentOS-7 - Extras                                                                                                  307

!ius/x86_64                                                                               IUS for Enterprise Linux 7 - x86_64                                                                                714

!updates/7/x86_64                                                                         CentOS-7 - Updates                                                                                                 997

repolist: 25,677


#yum repolist
Loaded plugins: product-id, search-disabled-repos, subscription-manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
repo id                                                                              repo name                                                                                                            status

nodesource/x86_64                                                                    Node.js Packages for Enterprise Linux 7 - x86_64                                                                         37

repolist: 55,117

DNF, or Dandified Yum, which is the next major version of the Yum package manager was introduced with Fedora 18. As of Fedora 22, it has become the default package manager.

https://www.rootusers.com/how-to-install-dnf-package-manager-in-centosrhel/

# 基础服务

# 网络

Ubuntu

注意,对于Ubuntu 17.10 switched from ifupdown (which uses the /etc/network/interfaces file) to netplan,

所以新版本已经找不到 /etc/network/interfaces

netplan貌似只是个接口: https://netplan.io/examples/

具体的控制还是: NetworkManager 和 networkd, 其中desktop版本默认是 NetworkManager，而对于无UI的server版本只能用networkd https://askubuntu.com/questions/1031439/am-i-running-networkmanager-or-networkd

To configure netplan, save configuration files under /etc/netplan/ with a .yaml extension (e.g. /etc/netplan/config.yaml), then run sudo netplan apply. This command parses and applies the configuration to the system. Configuration written to disk under /etc/netplan/ will persist between reboots.

---------------------------------------------------------
对于NetworkManager:
---------------------------------------------------------
First any interfaces defined in /etc/network/interfaces are ignored by network-manager. (man 5 NetworkManager)
systemctl status network-manager

vim /etc/netplan/01-network-manager-all.yaml
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager       

UI是使用NetworkManager,所以直接打开控制面板来设置静态IP和DNS即可
address 192.168.0.109
netmask 255.255.255.0
gateway 192.168.0.1
DNS: 8.8.8.8
设置完等一会即可    

---------------------------------------------------------
对于Networkd：
---------------------------------------------------------
systemd-networkd will only manage network addresses and routes for any link for which it finds a .network file with an appropriate [Match] section. (man 8 systemd-networkd).
systemctl status systemd-netword

vim /etc/netplan/01-network-manager-all.yaml
network:
    version: 2
    renderer: networkd
    ethernets:
        enp3s0:
            dhcp4: true

Debain based : Kali

--- for debain:
配置静态ip
/etc/network/interfaces：
#auto eth0
#iface eth0 inet dhcp
auto eth0
iface eth0 inet static
address 192.168.0.109
netmask 255.255.255.0
gateway 192.168.0.1

sudo ifdown eth0
sudo ifup eth0
or
sudo /etc/init.d/networking restart

如果还是无法上网（上面172.17.5.36是某ISP提供的，貌似虚拟机无法用）：
/etc/resolv.conf
nameserver 8.8.8.8

sudo systemctl restart systemd-resolved.service

解决后看下当前路由情况：
route -n

#Verify new IP settings:
ip a s eth0
#Verify new routing settings:
ip r
#Verify DNS servers settings:
cat /etc/resolv.conf
#Verify the internet connectivity:
ping -c 4 google.com

[email protected]:/home/lyhistory# ip -4 addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    inet 192.168.0.109/24 brd 192.168.0.255 scope global eth0
       valid_lft forever preferred_lft forever

[email protected]:/home/lyhistory# ip route
default via 192.168.0.1 dev eth0 onlink 
192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.109

Centos

--- for centos
vim /etc/sysconfig/network-scripts/ifcfg-eth0
HWADDR=00:08:A2:0A:BA:B8
TYPE=Ethernet
#BOOTPROTO=dhcp
BOOTPROTO=none	
# Server IP #
IPADDR=192.168.0.110
# Subnet #
PREFIX=24
# Set default gateway IP #
GATEWAY=192.168.0.1
# Set dns servers #
DNS1=8.8.8.8
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
# Disable ipv6 #
IPV6INIT=no
NAME=eth0
# This is system specific and can be created using 'uuidgen eth0' command #
UUID=41171a6f-bce1-44de-8a6e-cf5e782f8bd6
DEVICE=eth0
ONBOOT=yes

systemctl restart network