6.2. aptitude
、apt-get
和 apt
命令
APT is a vast project, whose original plans included a graphical interface. It is based on a library which contains the core application, and
apt-get
is the first front end — command-line based — which was developed within the project.
apt
is a second command-line based front end provided by APT which overcomes some design mistakes of
apt-get
.
Both tools are built on top of the same library and are thus very close, but the default behavior of apt
has been improved for interactive use and to actually do what most users expect. The APT developers reserve the right to change the public interface of this tool to further improve it. On the opposite, the public interface of apt-get
is well defined and will not change in any backwards incompatible way. It is thus the tool that you want to use when you need to script package installation requests.
Numerous other graphical interfaces then appeared as external projects: synaptic
, aptitude
(which includes both a text mode interface and a graphical one — even if not complete yet), wajig
, etc. The most recommended interface, apt
, is the one that we will use in the examples given in this section. Note, however, that apt-get
and aptitude
have a very similar command line syntax. When there are major differences between these three commands, these will be detailed.
For any work with APT, the list of available packages needs to be updated; this can be done simply through apt update
. Depending on the speed of your connection and configuration, the operation can take a while, since it involves downloading a certain number of (usually compressed) files (Packages
, Sources
, Translation-language-code
), which have gradually become bigger and bigger as Debian has developed (at least 10 MB of data for the main
section). Of course, installing from a CD-ROM/DVD set does not require any downloading — in this case, the operation is very fast.
With APT, packages can be added or removed from the system, respectively with apt install package
and apt remove package
. In both cases, APT will automatically install the necessary dependencies or delete the packages which depend on the package that is being removed. The apt purge package
command involves a complete uninstallation by deleting the configuration files as well.
If the file
sources.list
mentions several distributions, it is possible to give the version of the package to install. A specific version number can be requested with
apt install package=version
, but indicating its distribution of origin (
Stable,
Testing or
Unstable) — with
apt install package/distribution
— is usually preferred. With this command, it is possible to go back to an older version of a package (if, for instance, you know that it works well), provided that it is still available in one of the sources referenced by the
sources.list
file. Otherwise the
snapshot.debian.org
archive can come to the rescue (see sidebar
进阶旧包版本: snapshot.debian.org
).
例 6.4. Installation of the Unstable version of spamassassin
#
apt install spamassassin/unstable
If the package to install has been made available to you under the form of a simple .deb
file without any associated package repository, it is still possible to use APT to install it together with its dependencies (provided that the dependencies are available in the configured repositories) with a simple command: apt install ./path-to-the-package.deb
. The leading ./
is important to make it clear that we are referring to a filename and not to the name of a package available in one of the repositories.
常规升级是推荐的,因为它们包含最新的安全更新。要升级,可使用apt upgrade
、apt-get upgrade
、aptitude safe-upgrade
(当然需在apt update
之后)。该命令会查找要升级的已安装包,同时不移除任何包。也就是说,目标是确保可能的侵入式升级最小化。apt-get
命令略苛刻于 aptitude
或 apt
命令,因为它会拒绝安装未预先安装的软件包。
apt
会选择最新的版本号 (除了来自 实验版 与 稳定反向植入版,其缺省忽略版本号)。若指定 测试版 或 不稳定版 于 sources.list
内,则 apt upgrade
会把 稳定版 系统切换至 测试版 或 不稳定版,这些都不是您要的。
To tell apt
to use a specific distribution when searching for upgraded packages, you need to use the -t
or --target-release
option, followed by the name of the distribution you want (for example, apt -t stable upgrade
). To avoid specifying this option every time you use apt
, you can add APT::Default-Release "stable";
in the file /etc/apt/apt.conf.d/local
.
对于非常重要的升级,如从一个 Debian 主版本变更为下一版本,你需要使用apt full-upgrade
。使用此命令,apt
将会完全升级,即使必须移除一些废弃包或者安装新的依赖包。这也适用于日常使用 Debian Unstable并每天跟随其演化的用户。它是如此简便以至于几乎无需解释:APT的声誉基于此项强大的功能。
不同于 apt
与 aptitude
,apt-get
不知道 full-upgrade
命令。反而,您应使用 apt-get dist-upgrade
(”升级发行版”),此古老且知名的命令也被 apt
与 aptitude
接受给读者相当的便利。
The results of these operations are logged into /var/log/apt/history.log
and /var/log/apt/term.log
, whereas dpkg
keeps its log in a file called /var/log/dpkg.log
.
Besides the configuration elements already mentioned, it is possible to configure certain aspects of APT by adding directives in a file of the /etc/apt/apt.conf.d/
directory or /etc/apt/apt.conf
itself. Remember, for instance, that it is possible for APT to tell dpkg
to ignore file conflict errors by specifying DPkg::options { "--force-overwrite"; }
.
若只能经由代理服务器近用网页,添加像这样的一列
Acquire::http::proxy "http://yourproxy:3128"
。对 FTP 代理服务器,用
Acquire::ftp::proxy "ftp://yourproxy"
。更多的配置选项,参考
apt.conf(5) 手册页以
man apt.conf
命令 (手删的详情,见
第 7.1.1 节 “手册页面”) 查看。
配置 APT 最重要的层面之一是管理每个软件包来源的优先性。例如,从 测试版、不稳定 或 实验版 中选取一个或多个软件包。可以指令每个软件包的优先性 (视其版本或发行版,同个软件包可以有多个优先性)。这些优先性将影响 APT 的行为:每个软件包总是选择最优先的版本 (除非旧于已安装的版本或优先性小于 1000)。
APT 设置若干缺省的优先性。已安装软件包版本的优先性是 100。未安装版本缺省优先性为 500,若是另个发布的目标则可跳至 990 (以 -t
命令行选项或 APT::Default-Release
配置指令调整)。
You can modify the priorities by adding entries in a file in /etc/apt/preferences.d/
or the /etc/apt/preferences
file with the names of the affected packages, their version, their origin and their new priority.
APT will never install an older version of a package (that is, a package whose version number is lower than the one of the currently installed package) except if its priority is higher than 1000 (or it is explicitely requested by the user, see
第 6.2.2 节 “安装和卸载”). APT will always install the highest priority package which follows this constraint. If two packages have the same priority, APT installs the newest one (whose version number is the highest). If two packages of same version have the same priority but differ in their content, APT installs the version that is not installed (this rule has been created to cover the case of a package update without the increment of the revision number, which is usually required).
In more concrete terms, a package whose priority is
- < 0
will never be installed,
- 1..99
will only be installed if no other version of the package is already installed,
- 100..499
will only be installed if there is no other newer version installed or available in another distribution,
- 500....989
will only be installed if there is no newer version installed or available in the target distribution,
- 990..1000
will be installed except if the installed version is newer,
- > 1000
will always be installed, even if it forces APT to downgrade to an older version.
When APT checks /etc/apt/preferences
and /etc/apt/preferences.d/
, it first takes into account the most specific entries (often those specifying the concerned package), then the more generic ones (including, for example, all the packages of a distribution). If several generic entries exist, the first match is used. The available selection criteria include the package's name and the source providing it. Every package source is identified by the information contained in a Release
file that APT downloads together with the Packages
files. It specifies the origin (usually “Debian” for the packages of official mirrors, but it can also be a person's or an organization's name for third-party repositories). It also gives the name of the distribution (usually Stable, Testing, Unstable or Experimental for the standard distributions provided by Debian) together with its version (for example, 10 for Debian Buster). Let's have a look at its syntax through some realistic case studies of this mechanism.
暂时假设您只需用到 Debian 稳定版的软件包。除非特别指明,不会安装其他版本的软件包。可以在 /etc/apt/preferences
文件内写入以上的条目:
a=stable
设置发行版的名称。o=Debian
限制来自 “Debian” 的软件包。
Let's now assume that you have a server with several local programs depending on the version 5.24 of Perl and that you want to ensure that upgrades will not install another version of it. You could use this entry:
To gain a better understanding of the mechanisms of priority and distribution or repository properties to pin do not hesitate to execute
apt-cache policy
to display the default priority associated with each package source, or
apt-cache policy package
to display the default priority for each available version and source of a package as explained in
秘诀 apt-cache policy
.
The reference documentation for the files /etc/apt/preferences
and /etc/apt/preferences.d/
is available in the manual page apt_preferences(5), which you can display with man apt_preferences
.
apt
是很奇妙的工具,可从其他发行版提取软件包。例如,安装 稳定版 系统之后,或许想要在不偏离系统原来状态下,试试 测试版 或 不稳定版 的软件包。
混用不同版本软件包出问题时,Even if you will occasionally encounter problems while mixing packages from different distributions,
apt
可以处理得极为恰当把风险降到最低。最好的方法是把所有的发行版置于
/etc/apt/sources.list
文件内 (某些人总是置入三个发行版,不过还是要记得
不稳定版 是有经验用户的专属。) 且在
APT::Default-Release
参数中设置偏好的发行版 (见
第 6.2.3 节 “系统升级”) 。
假设 稳定版 是您的参考版本,但是 测试版 与 不稳定版 也列在 sources.list
文件内。在这个情况下,您可使用 apt install 软件包名称/testing
安装来自 测试版 的软件包。若因相依性未满足而安装失败,可以在 测试版 内加入 -t testing
参数。同样的方式也适用于 不稳定版。
在此情况下,除了已经被其他发行版升级之外,升级 (
upgrade
与
full-upgrade
) 只在
稳定版 内完成:其他的升级在各自的发行版内处理。稍后以 APT 缺省的优先性说明此行为。请使用
apt-cache policy
(见专栏
秘诀 apt-cache policy
) 查看指定的优先性。
每件事都围绕在 APT 只处理高于或等于已安装版本号软件包的前提下 (假设 /etc/apt/preferences
还未强迫优先性高于 1000 的某些软件包)。
假设从Let's assume that you have installed version 1 of a first package from 稳定版 安装第一个软件包的第一版且从and that version 2 and 3 are available respectively in 测试版 与 不稳定版 安装同软件包的第二版与第三版水。已安装的版本优先性为 100 但在but the version available in 稳定版 (相同的) 优先性为 990 (因为它是目标发布版的一部分)。在 测试版 与 不稳定版 的软件包其优先性为 500 (缺省不安装版本的优先性)。获选者为优先性 990 的版本1。软件包 “留在 稳定版 内”。
Let's take the example of another package whose version 2 has been installed from Testing. Version 1 is available in Stable and version 3 in Unstable. Version 1 (of priority 990 — thus lower than 1000) is discarded because it is lower than the installed version. This only leaves version 2 and 3, both of priority 500. Faced with this alternative, APT selects the newest version, the one from Unstable. If you don't want a package installed from Testing to migrate to Unstable, you have to assign a priority lower than 500 (490 for example) to packages coming from Unstable. You can modify /etc/apt/preferences
to this effect:
Package: *
Pin: release a=unstable
Pin-Priority: 490
One of the essential functionalities of apt
is the tracking of packages installed only through dependencies. These packages are called “automatic”, and often include libraries.
With this information, when packages are removed, the package managers can compute a list of automatic packages that are no longer needed (because there is no “manually installed” packages depending on them). apt-get autoremove
or apt autoremove
will get rid of those packages. aptitude
does not have this command because it removes them automatically as soon as they are identified. In all cases, the tools display a clear message listing the affected packages.
把软件包标记为自动是个好习惯,不需要时就被自动移除。
apt-mark auto 软件包名称
会标记该软件包为自动而
apt-mark manual 软件包名称
则不标记。
aptitude markauto
与
aptitude unmarkauto
作用相同只是功能较多 (见
第 6.5.1 节 “aptitude
”)。命令交互接口的
aptitude
也可查看多个软件包的 “自动旗标”。
自动安装软件包出现在系统内。系由于从命令行取得该等信息,可使用 aptitude why 软件包名称
(apt
与 apt-get
没有类似的功能):
$
aptitude why python-debian
i aptitude Suggests apt-xapian-index
p apt-xapian-index Depends python-debian (>= 0.1.14)