control
文件
dpkg
来操作软件包
dpkg
的数据库,并检查 .deb
文件
dpkg
的日志文件
作为 Debian 系统管理员,你经常地要处理
.deb
包,因为它们包含一致的功能单元(应用程序、文档等),使得安装和维护更容易。所以了解它们是什么及如何使用它们是个好主意。 This chapter describes the structure and contents of “binary” and “source” packages. The former are files directly usable by
dpkg
, while the latter contain the source code, as well as instructions for building binary packages.
The Debian package format is designed so that its content may be extracted on any Unix system that has the classic commands
ar
,
tar
, and
xz
or sometimes
gzip
or
bzip2
. This seemingly trivial property is important for portability and disaster recovery. Imagine, for example, that you mistakenly deleted the
dpkg
program, and that you could thus no longer install Debian packages.
dpkg
being a Debian package itself, it would seem your system would be done for... Fortunately, you know the format of a package and can therefore download the
.deb
file of the
dpkg package and install it manually (see sidebar
工具
dpkg
、
APT
和
ar
). If by some misfortune one or more of the programs
ar
,
tar
or
gzip
/
xz
/
bzip2
have disappeared, you will only need to copy the missing program from another system (since each of these operates in a completely autonomous manner, without dependencies, a simple copy will suffice). If your system suffered some even more outrageous fortune, and even these don't work (maybe the deepest system libraries are missing?), you should try the static version of
busybox
(provided in the
busybox-static package), which is even more self-contained, and provides subcommands such as
busybox ar
,
busybox tar
and
busybox xz
.
In case of a misfortune you better also have a backup of your system (see 第 9.10 节 “备份”).
工具 dpkg
、APT
和 ar
dpkg
is the program that handles
.deb
files (binary packages), notably extracting, analyzing, and unpacking them. APT (the abbreviation of "Advanced Packaging Tool") is a group of programs that allows the execution of higher-level modifications to the system: installing or removing a package (while keeping dependencies satisfied), updating and upgrading the system, listing the available packages, etc. As for the
ar
program, it allows handling files of the same name:
ar t archive
displays the list of files contained in such an archive,
ar x archive
extracts the files from the archive into the current working directory,
ar d archive file
deletes a file from the archive, etc. Its man page (
ar(1)) documents all its other features.
ar
is a very rudimentary tool that a Unix administrator would only use on rare occasions, but admins routinely use
tar
, a more evolved archive and file management program. This is why it is easy to restore
dpkg
in the event of an erroneous deletion. You would only have to download the Debian package and extract the content from the
data.tar.xz
archive in the system's root (
/
):
#
ar x dpkg_1.19.7_amd64.deb
#
tar -C / -p -xJf data.tar.xz
基础知识 Man 手册注记
初学者可能会在看到“
ar(1)”这样的文字注记时感到疑惑。这通常是个简写,它表示指向 man 手册第一类中标题是
ar
的页面。 有时这种注记也用来避免歧义,比如要区分清楚是
printf
命令,可以用
printf(1) 来指明,如果是 C 语言里的
printf
函数,就可以用
printf(3) 来引用。 第 7 章
问题的解决与相关信息的检索 更详细地讨论手册页 (参见 第 7.1.1 节 “手册页面”)。 来看看
.deb
文件的内容:
$
ar t dpkg_1.19.7_amd64.deb
debian-binary control.tar.gz data.tar.xz $
ar x dpkg_1.19.7_amd64.deb
$
ls
control.tar.gz data.tar.xz debian-binary dpkg_1.19.7_amd64.deb $
tar tJf data.tar.xz | head -n 16
./ ./ ./etc/ ./etc/alternatives/ ./etc/alternatives/README ./etc/cron.daily/ ./etc/cron.daily/dpkg ./etc/dpkg/ ./etc/dpkg/dpkg.cfg ./etc/dpkg/dpkg.cfg.d/ ./etc/logrotate.d/ ./etc/logrotate.d/alternatives ./etc/logrotate.d/dpkg ./sbin/ ./sbin/start-stop-daemon ./usr/ ./usr/bin/ $
tar tJf control.tar.xz
./ ./conffiles ./control ./md5sums ./postinst ./postrm $
cat debian-binary
2.0
如你所见, Debian 包的
ar
存档格式由三个文件组成:
debian-binary
.deb
file package format version. In Debiancontrol.tar.xz
data.tar.xz
, data.tar.bz2
, data.tar.gz
xz
,bzip2
orgzip
.
当前题目:【Debian管理员手册】第 5 章 包管理系统:工具和基本原则
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