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5.4. 通过dpkg来操作软件包

dpkg 是系统层面处理 Debian 软件包的基础指令。若您有 .deb 软件包,可以用 dpkg 安装及分析其内容。但此指令只能看到 Debian 世界的部分内容:它知道系统安装那些软件包、指令列给了那些参数,但不知道还有那些可用的软件包。因此,没有相依性就完了。apt 之类的工具,则可产生相依性清单,尽量自动安装软件包。

5.4.1. 安装软件包

首先,dpkg 是安装 Debian 已经可用软件包的工具 (因为不需下载任何东西)。我们使用它的 -i--install 选项。

例 5.2. 通过dpkg来安装一个软件包

# dpkg -i man-db_2.7.6.1-2_amd64.deb
(Reading database ... 110431 files and directories currently installed.)
Preparing to unpack man-db_2.7.6.1-2_amd64.deb ...
Unpacking man-db (2.7.6.1-2) over (2.7.6.1-1) ...
Setting up man-db (2.7.6.1-2) ...
Updating database of manual pages ...
Processing triggers for mime-support (3.60) ...
通过dpkg我们可以看到安装时的不同步骤;因此我们会知道在什么时候可能会发生错误。安装也被分为两个阶段:首先解压包,然后配置它。apt-get会利用这一点,然后有限的调用dpkg(因为每次调用都要把数据加载到内存中,特别是那些在名单中已经被安装的文件)。

例 5.3. 分开解压和配置

# dpkg --unpack man-db_2.7.6.1-2_amd64.deb
(Reading database ... 110431 files and directories currently installed.)
Preparing to unpack man-db_2.7.6.1-2_amd64.deb ...
Unpacking man-db (2.7.6.1-2) over (2.7.6.1-2) ...
Processing triggers for mime-support (3.60) ...
# dpkg --configure man-db
Setting up man-db (2.7.6.1-2) ...
Updating database of manual pages ...
有时dpkg在安装软件包的时候会失败并且返回一个错误;如果用户命令dpkg忽略掉这个错误,那么它仅仅会提示一个警告;这也就是我们有一个不同的--force--*选项。dpkg --force-help,或者是dpkg的帮助文档,有一个这些选项的详细清单。最常见的错误是,你迟到会遇到这样一个文件冲突,当一个软件包包含的文件中已经安装了另外一个软件包。:
Unpacking libgdm (from .../libgdm_3.8.3-2_amd64.deb) ...
dpkg: 处理 /var/cache/apt/archives/libgdm_3.8.3-2_amd64.deb (--unpack) 时发生错误:
 试图覆写 '/usr/bin/gdmflexiserver',也同时在软件包 gdm3 3.4.1-9 内
在这种情况下,如果你认为文件替换该文件可能不会对系统的稳定性造成重大的风险(通常情况下),你可以使用--force-overwrite选项来告诉dpkg去忽略这个错误并且覆盖该文件。
当然这里有非常多的--force-*选项,只是--force-overwrite使用的非常频繁。这些选项仅存在特殊的情况下,所以最好是不去使用它们以便遵守软件包的管理机制。不要忘了,这些管理规则可以确保你的系统的稳定性和一致性。

5.4.2. 软件包移除

使用 dpkg 加上 -r--remove 选项,再加上软件包名称,就可移除该软件包。然而,这种方式的移除并不完整:仍保留所有的配置文件、维护脚本、记录文件 (系统记录档) 及该软件包的其他用户数据。这种方式是停用程序,仍可以相同的配置快速地再安装回来。完全移除该软件包的所有相关文件,应使用 -P--purge 选项,再加上软件包名称。

例 5.4. 移除与清除 debian-cd 软件包

# dpkg -r debian-cd
(Reading database ... 112188 files and directories currently installed.)
Removing debian-cd (3.1.20) ...
# dpkg -P debian-cd
(Reading database ... 111613 files and directories currently installed.)
Purging configuration files for debian-cd (3.1.20) ...

5.4.3. 查询 dpkg 的数据库,并检查 .deb 文件

做结论前,我们将学习查找内部数据库以获取信息的 dpkg 选项。先给长版的选项再给对应的短版选项 (其参数是一样的) 以 --listfiles 软件包 (或 -L) 为例,列出该软件包安装的文件清单;--search 文件 (或 -S),寻找包括该文件的套性;--status 软件包 (或 -s),显示该软件包的标头;--list (或 -l),显示该系统内软件包清单与安装状态;--contents file.deb (或 -c),列出 Debian 指定软件包清单;--info file.deb (或 -I),列出该软件包的标头。

例 5.5. dpkg的各种查询

$ dpkg -L base-passwd
/.
/usr
/usr/sbin
/usr/sbin/update-passwd
/usr/share
/usr/share/base-passwd
/usr/share/base-passwd/group.master
/usr/share/base-passwd/passwd.master
/usr/share/doc
/usr/share/doc/base-passwd
/usr/share/doc/base-passwd/README
/usr/share/doc/base-passwd/changelog.gz
/usr/share/doc/base-passwd/copyright
/usr/share/doc/base-passwd/users-and-groups.html
/usr/share/doc/base-passwd/users-and-groups.txt.gz
/usr/share/doc-base
/usr/share/doc-base/users-and-groups
/usr/share/lintian
/usr/share/lintian/overrides
/usr/share/lintian/overrides/base-passwd
/usr/share/man
/usr/share/man/de
/usr/share/man/de/man8
/usr/share/man/de/man8/update-passwd.8.gz
/usr/share/man/es
/usr/share/man/es/man8
/usr/share/man/es/man8/update-passwd.8.gz
/usr/share/man/fr
/usr/share/man/fr/man8
/usr/share/man/fr/man8/update-passwd.8.gz
/usr/share/man/ja
/usr/share/man/ja/man8
/usr/share/man/ja/man8/update-passwd.8.gz
/usr/share/man/man8
/usr/share/man/man8/update-passwd.8.gz
/usr/share/man/pl
/usr/share/man/pl/man8
/usr/share/man/pl/man8/update-passwd.8.gz
/usr/share/man/ru
/usr/share/man/ru/man8
/usr/share/man/ru/man8/update-passwd.8.gz
$ dpkg -S /bin/date
coreutils: /bin/date
$ dpkg -s coreutils
Package: coreutils
Essential: yes
Status: install ok installed
Priority: required
Section: utils
Installed-Size: 15103
Maintainer: Michael Stone <mstone@debian.org>
Architecture: amd64
Multi-Arch: foreign
Version: 8.26-3
Replaces: mktemp, realpath, timeout
Pre-Depends: libacl1 (>= 2.2.51-8), libattr1 (>= 1:2.4.46-8), libc6 (>= 2.17), libselinux1 (>= 2.1.13)
Conflicts: timeout
Description: GNU core utilities
 This package contains the basic file, shell and text manipulation
 utilities which are expected to exist on every operating system.
 .
 Specifically, this package includes:
 arch base64 basename cat chcon chgrp chmod chown chroot cksum comm cp
 csplit cut date dd df dir dircolors dirname du echo env expand expr
 factor false flock fmt fold groups head hostid id install join link ln
 logname ls md5sum mkdir mkfifo mknod mktemp mv nice nl nohup nproc numfmt
 od paste pathchk pinky pr printenv printf ptx pwd readlink realpath rm
 rmdir runcon sha*sum seq shred sleep sort split stat stty sum sync tac
 tail tee test timeout touch tr true truncate tsort tty uname unexpand
 uniq unlink users vdir wc who whoami yes
Homepage: http://gnu.org/software/coreutils
$ dpkg -l 'b*'
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                 Version         Architecture    Description
+++-====================-===============-===============-=============================================
un  backupninja          <none>          <none>          (no description available)
un  backuppc             <none>          <none>          (no description available)
un  baekmuk-ttf          <none>          <none>          (no description available)
un  base                 <none>          <none>          (no description available)
un  base-config          <none>          <none>          (no description available)
ii  base-files           9.9+deb9u1      amd64           Debian base system miscellaneous files
ii  base-passwd          3.5.43          amd64           Debian base system master password and group 
ii  bash                 4.4-5           amd64           GNU Bourne Again SHell
[...]
$ dpkg -c /var/cache/apt/archives/gnupg_2.1.18-8~deb9u1_amd64.deb
drwxr-xr-x root/root         0 2017-09-18 20:41 ./
drwxr-xr-x root/root         0 2017-09-18 20:41 ./usr/
drwxr-xr-x root/root         0 2017-09-18 20:41 ./usr/bin/
-rwxr-xr-x root/root    996648 2017-09-18 20:41 ./usr/bin/gpg
-rwxr-xr-x root/root      3444 2017-09-18 20:41 ./usr/bin/gpg-zip
-rwxr-xr-x root/root    161192 2017-09-18 20:41 ./usr/bin/gpgconf
-rwxr-xr-x root/root     26696 2017-09-18 20:41 ./usr/bin/gpgparsemail
-rwxr-xr-x root/root     76112 2017-09-18 20:41 ./usr/bin/gpgsplit
-rwxr-xr-x root/root    158344 2017-09-18 20:41 ./usr/bin/kbxutil
-rwxr-xr-x root/root      1081 2014-06-25 16:17 ./usr/bin/lspgpot
-rwxr-xr-x root/root      2194 2017-09-18 20:41 ./usr/bin/migrate-pubring-from-classic-gpg
-rwxr-xr-x root/root     14328 2017-09-18 20:41 ./usr/bin/watchgnupg
drwxr-xr-x root/root         0 2017-09-18 20:41 ./usr/sbin/
-rwxr-xr-x root/root      3078 2017-09-18 20:41 ./usr/sbin/addgnupghome
-rwxr-xr-x root/root      2219 2017-09-18 20:41 ./usr/sbin/applygnupgdefaults
drwxr-xr-x root/root         0 2017-09-18 20:41 ./usr/share/
drwxr-xr-x root/root         0 2017-09-18 20:41 ./usr/share/doc/
drwxr-xr-x root/root         0 2017-09-18 20:41 ./usr/share/doc/gnupg/
-rw-r--r-- root/root     18964 2017-01-23 18:39 ./usr/share/doc/gnupg/DETAILS.gz
[...]
$ dpkg -I /var/cache/apt/archives/gnupg_2.1.18-8~deb9u1_amd64.deb
 new debian package, version 2.0.
 size 1124042 bytes: control archive=2221 bytes.
    1388 bytes,    24 lines      control              
    2764 bytes,    43 lines      md5sums              
 Package: gnupg
 Source: gnupg2
 Version: 2.1.18-8~deb9u1
 Architecture: amd64
 Maintainer: Debian GnuPG Maintainers <pkg-gnupg-maint@lists.alioth.debian.org>
 Installed-Size: 2088
 Depends: gnupg-agent (= 2.1.18-8~deb9u1), libassuan0 (>= 2.0.1), libbz2-1.0, libc6 (>= 2.15), libgcrypt20 (>= 1.7.0), libgpg-error0 (>= 1.14), libksba8 (>= 1.3.4), libreadline7 (>= 6.0), libsqlite3-0 (>= 3.7.15), zlib1g (>= 1:1.1.4)
 Recommends: dirmngr (= 2.1.18-8~deb9u1), gnupg-l10n (= 2.1.18-8~deb9u1)
 Suggests: parcimonie, xloadimage
 Breaks: debsig-verify (<< 0.15), dirmngr (<< 2.1.18-8~deb9u1), gnupg2 (<< 2.1.11-7+exp1), libgnupg-interface-perl (<< 0.52-3), libgnupg-perl (<= 0.19-1), libmail-gnupg-perl (<= 0.22-1), monkeysphere (<< 0.38~), php-crypt-gpg (<= 1.4.1-1), python-apt (<= 1.1.0~beta4), python-gnupg (<< 0.3.8-3), python3-apt (<= 1.1.0~beta4)
 Replaces: gnupg2 (<< 2.1.11-7+exp1)
 Provides: gpg
 Section: utils
 Priority: optional
 Multi-Arch: foreign
 Homepage: https://www.gnupg.org/
 Description: GNU privacy guard - a free PGP replacement
  GnuPG is GNU's tool for secure communication and data storage.
  It can be used to encrypt data and to create digital signatures.
  It includes an advanced key management facility and is compliant
  with the proposed OpenPGP Internet standard as described in RFC4880.
[...]

5.4.4. dpkg的日志文件

dpkg 把所有的交易记录存在名为 /var/log/dpkg.log 的日志档。这个日志档的内容颇为详尽且啰唆,记录软件包被 dpkg 处理的每个进程。追踪 dpkg 的每个作为之外,日志档还保留系统发展的记录:可以覆查每个软件包的安装与移除步骤,对于了解最近的变动极有帮助。此外,还记录所有的版本,可以交互检查 changelog.Debian.gz 的内容,查看有问题的软件包或在线的错误报告。

5.4.5. 多架构支持

所有的 Debian 包在它们的管控信息中都有一个架构 字段。该字段可包含:“全部“(对与架构无关的包),或者它的目标架构名称(如“amd64”, “armhf”,…)。对于后者,默认情况下,dpkg将只能接受安装与主机架构匹配的软件包,主机架构可通过dpkg --print-architecture来获得。
该限制确保用户不会因为错误架构编译的二进制文件而挂掉。一切都很完美,除了(某些)计算机可以运行多架构的二进制文件,或者以本地方式(“amd64“系统可运行”i386“二进制文件)运行,或者以模拟器运行。

5.4.5.1. 启用多架构

dpkg的多架构支持允许用户定义可安装于当前系统的“异质架构” 。这可以方便的通过 dpkg --add-architecture完成,如下例。有一相应的 dpkg --remove-architecture 以放弃对异质架构的支持,但仅可用于未余留该架构软件包的情况。
# dpkg --print-architecture
amd64
# dpkg --print-foreign-architectures
# dpkg -i gcc-6-base_6.3.0-18_armhf.deb
dpkg: error processing archive gcc-6-base_6.3.0-18_armhf.deb (--install):
 package architecture (armhf) does not match system (amd64)
Errors were encountered while processing:
 gcc-6-base_6.3.0-18_armhf.deb
# dpkg --add-architecture armhf
# dpkg --add-architecture armel
# dpkg --print-foreign-architectures
armhf
armel
# dpkg -i gcc-6-base_6.3.0-18_armhf.deb
Selecting previously unselected package gcc-6-base:armhf.
(Reading database ... 112000 files and directories currently installed.)
Preparing to unpack gcc-6-base_6.3.0-18_armhf.deb ...
Unpacking gcc-6-base:armhf (6.3.0-18) ...
Setting up gcc-6-base:armhf (6.3.0-18) ...
# dpkg --remove-architecture armhf
dpkg: error: cannot remove architecture 'armhf' currently in use by the database
# dpkg --remove-architecture armel
# dpkg --print-foreign-architectures
armhf

5.4.5.2. 多架构相关的变更

To make multi-arch actually useful and usable, libraries had to be repackaged and moved to an architecture-specific directory so that multiple copies (targeting different architectures) can be installed alongside. Such updated packages contain the “Multi-Arch: same” header field to tell the packaging system that the various architectures of the package can be safely co-installed (and that those packages can only satisfy dependencies of packages of the same architecture). The most important libraries have been converted since the introduction of multi-arch in Debian Wheezy, but there are many libraries that will likely never be converted unless someone specifically requests it (through a bug report for example).
$ dpkg -s gcc-6-base
dpkg-query: error: --status needs a valid package name but 'gcc-6-base' is not: ambiguous package name 'gcc-6-base' with more than one installed instance

Use --help for help about querying packages.
$ dpkg -s gcc-6-base:amd64 gcc-6-base:armhf | grep ^Multi
Multi-Arch: same
Multi-Arch: same
$ dpkg -L libgcc1:amd64 |grep .so
/lib/x86_64-linux-gnu/libgcc_s.so.1
$ dpkg -S /usr/share/doc/gcc-6-base/copyright
gcc-6-base:amd64, gcc-6-base:armhf: /usr/share/doc/gcc-6-base/copyright
值得注意的是,Multi-Arch: same软件包需具备能够明晰识别架构的名称。它们也能够与相同包的其他实例共享文件;dpkg确保所有的包在共享时具有逐位对应识别的文件。最后但并非最不重要的,一个包的所有实例必须为相同版本。它们必须同时升级。
多架构支持也带来了在依赖处理方式上的一些有趣的挑战。要满足依赖,需要:或者有Multi-Arch: foreign标识的软件包,或者架构上能匹配已声明依赖的软件包(在该依赖方案处理中,架构无关包假定为同样架构,而非主机架构)。通过 软件包 :any语法,依赖可以被弱化,以便允许任意架构能够满足依赖,但异质软件包仅能满足如下依赖:有“ Multi-Arch: allowed ”标识的依赖。