Linux系统具有强大的包管理能力

一、包管理基本原理

Linux系统具有强大的包管理能力，能够自动从互联网的软件仓库中搜索、安装、升级、卸载软件或操作系统。其基本原理为：

1. 厂商或开源组织将软件包放至服务器中，构成源或软件仓库，以供用户下载使用；
2. 软件仓库有很多，国内常用的源有阿里源、清华源等等。Ubuntu源信息记录在/etc/apt/sources.list中

root@linux:/var/lib/apt/lists$ cat/etc/apt/sources.list deb http://mirrors.aliyun.com/ubuntu/ bionicmain restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiversedeb [arch=amd64] http://mirrors.aliyun.com/docker-ce/linux/ubuntu bionic stable# deb-src [arch=amd64] http://mirrors.aliyun.com/docker-ce/linux/ubuntu bionic stable

3. 执行apt-get update命令，则会根据/etc/apt/sources.list记录的源站信息，扫描源服务器，并建立软件包的索引文件，存放在/var/lib/apt/lists/中

root@linux:/var/lib/apt/lists# lltotal222044drwxr-xr-x4root root12288Feb710:17./ drwxr-xr-x5root root4096Nov132020../ drwxr-xr-x2_apt root4096Nov162020auxfiles/ -rw-r-----1root root0Nov162020lock -rw-r--r--1root root74562Feb707:11mirrors.aliyun.com_ubuntu_dists_bionic-backports_InRelease -rw-r--r--1root root59629Dec1600:17mirrors.aliyun.com_ubuntu_dists_bionic-backports_main_binary-amd64_Packages -rw-r--r--1root root12910Dec1600:17mirrors.aliyun.com_ubuntu_dists_bionic-backports_main_i18n_Translation-en -rw-r--r--1root root17863Dec1600:17mirrors.aliyun.com_ubuntu_dists_bionic-backports_main_source_Sources -rw-r--r--1root root49624Dec1602:14mirrors.aliyun.com_ubuntu_dists_bionic-backports_universe_binary-amd64_Packages -rw-r--r--1root root15723Dec1602:14mirrors.aliyun.com_ubuntu_dists_bionic-backports_universe_i18n_Translation-en -rw-r--r--1root root20023Dec1602:14mirrors.aliyun.com_ubuntu_dists_bionic-backports_universe_source_Sources -rw-r--r--1root root242048Apr272018mirrors.aliyun.com_ubuntu_dists_bionic_InRelease ......

进一步，查看文件的信息，则：

root@linux:/var/lib/apt/lists# cat mirrors.aliyun.com_ubuntu_dists_bionic_InRelease | more-----BEGINPGP SIGNED MESSAGE-----Hash:SHA512Origin:UbuntuLabel:UbuntuSuite:bionicVersion:18.04Codename:bionicDate:Thu,26Apr201823:37:48UTCArchitectures:amd64arm64 armhf i386 ppc64el s390xComponents:main restricted universe multiverseDescription:Ubuntu Bionic18.04MD5Sum:32a92a5c20f378d42dd2d2f4f28f6637628836439Contents-amd64 53c6a594819b51a5755f88b45d1eff7f37766986Contents-arm64.gz cd7bf6d50403da4348ee48138eace986585939706Contents-ppc64el af42d07307c5d1398c75e28986b36509616261664Contents-i386 98f43960ac7029b4948a13614038593c584794633Contents-armhf 31848d4faedf11946ff1af9c281f4e6b39528051Contents-amd64.gz

4. 执行apt-get install XXX，则会根据软件包的索引文件，找到最新版本的软件包及其依赖关系，下载(或更新)、解压、安装和配置软件包。

root@linux:/var/lib/apt/lists# apt-get install gitReading package lists... Done Building dependency tree Reading state information... Done The following package was automatically installedandis no longerrequired:grub-pc-bin Use'apt autoremove'to remove it. Suggestedpackages:git-daemon-run| git-daemon-sysvinit git-doc git-el git-email git-gui gitk gitweb git-cvs git-mediawiki git-svn The following packages will be upgraded: git 1 upgraded, 0 newly installed, 0 to removeand315notupgraded.

5. 执行apt-get upgrade，则可以将所有软件包一次性升级到最新版本。

root@linux:/var/lib/apt/lists# apt-get upgrade ...... Updating certificates in/etc/ssl/certs...0added,0removed; done. Running hooks in/etc/ca-certificates/update.d... done. done. Processing triggersforinitramfs-tools (0.130ubuntu3.13) ... update-initramfs: Generating/boot/initrd.img-4.15.0-122-generic

二、工具apt-get和apt区别：

1. Ubuntu 16.04版本前，使用apt-get、apt-cache和apt-config进行包的管理；存在的问题：命令过于分散，并且apt-cache和apt-config用得比较少。
2. Ubuntu 16.04版本发布时，引入apt命令以解决命令分散的问题；存在的问题：apt并未完全取代apt-get命令。

apt命令 原有命令 命令的功能 apt install apt-getinstall 安装软件包 apt remove apt-getremove 移除软件包 apt purge apt-getpurge 移除软件包及配置文件 aptupdateapt-getupdate刷新存储库索引 apt upgrade apt-getupgrade 升级所有可升级的软件包 apt autoremove apt-getautoremove 自动删除不需要的包 aptfull-upgrade apt-getdist-upgrade 在升级软件包时自动处理依赖关系 aptsearchapt-cachesearch 搜索应用程序 apt show apt-cacheshow 显示安装细节