找到了一种方法。
诀窍是使用两个固定从句。第一个是禁止从PPA安装所有软件包,第二个是选择您想要的软件包。
因此,对于上面的示例,我首先像往常一样添加ppa:
$ sudo add-apt-repository ppa:webapps/preview
...
$ sudo apt-get update
...
现在如果我运行apt-cache policy,它会显示有一个更新版本的chromium-browser可用,并且它将通过升级安装,因为它与我的当前chromium-browser具有相同的优先级(500)。
$ sudo apt-cache policy chromium-browser
chromium-browser:
Installed: 18.0.1025.168~r134367-0ubuntu0.12.04.1
Candidate: 20.0.1132.47~r144678-0precise1+webapps3
Version table:
20.0.1132.47~r144678-0precise1+webapps3 0
500 http://ppa.launchpad.net/webapps/preview/ubuntu/ precise/main amd64 Packages
*** 18.0.1025.168~r134367-0ubuntu0.12.04.1 0
500 http://us.archive.ubuntu.com/ubuntu/ precise-updates/universe amd64 Packages
500 http://security.ubuntu.com/ubuntu/ precise-security/universe amd64 Packages
500 http://ppa.launchpad.net/chromium-daily/beta/ubuntu/ precise/main amd64 Packages
100 /var/lib/dpkg/status
18.0.1025.151~r130497-0ubuntu1 0
500 http://us.archive.ubuntu.com/ubuntu/ precise/universe amd64 Packages
E: Unable to parse package file /etc/apt/preferences.d/webapps-preview-pin-400 (1)
$
这个包还不错,但我不想安装这个ppa中的其他包(它们也有500的优先级)。如果我现在尝试升级,我会从该软件源获取到更多不只是我想要的chromium包。
$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
bamfdaemon gwibber gwibber-service gwibber-service-facebook gwibber-service-twitter indicator-appmenu libbamf0 libbamf3-0 shotwell
The following packages will be upgraded:
chromium-browser chromium-browser-l10n chromium-codecs-ffmpeg gwibber-service-identica indicator-messages indicator-status-provider-mc5
indicator-status-provider-pidgin libindicator-messages-status-provider1
8 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.
Need to get 25.3 MB of archives.
After this operation, 5,034 kB of additional disk space will be used.
Do you want to continue [Y/n]?
所以我可以告诉apt,我希望那个ppa中的所有软件包,这里是webapps-preview,除了名字中带有"chromium"的软件包之外,都具有较低的优先级。实现这一机制的方法是
固定一个软件包。
我在/etc/apt/preferences.d/目录下创建了一个文件,其中包含两个子句。第一个子句表示给webapps-preview ppa中的所有软件包一个比普通软件包更低的优先级(即使它们具有更高的版本号,也不会被优先选择)。第二个子句部分地覆盖了第一个子句,它表示给那个ppa中名字中带有"chromium"的软件包与其他软件包相同的优先级,以便安装该软件包(因为它具有更高的版本号)。
$ cat /etc/apt/preferences.d/webapps-preview-pin-400
Package: *
Pin: release o=LP-PPA-webapps-preview
Pin-Priority: 400
Package: *chromium*
Pin: release o=LP-PPA-webapps-preview
Pin-Priority: 500
要识别“Pin: release”选项的正确字符串,我们可以再次使用apt-cache policy。
$ apt-cache policy
...
500 http://ppa.launchpad.net/webapps/preview/ubuntu/ precise/main i386 Packages
release v=12.04,o=LP-PPA-webapps-preview,a=precise,n=precise,l=preview,c=main
origin ppa.launchpad.net
...
对于apt版本小于0.8.14的情况,必须明确指定固定的软件包,因为通配符无法使用。
$ cat /etc/apt/preferences.d/webapps-preview-pin-400
Package: *
Pin: release o=LP-PPA-webapps-preview
Pin-Priority: 400
Package: chromium-browser chromium-codecs-ffmpeg chromium-browser-l10n chromium-codecs-ffmpeg-extra
Pin: release o=LP-PPA-webapps-preview
Pin-Priority: 500
现在,当我尝试升级时,我只从那个ppa获取我想要的软件包,而不是其他的。所有的软件包都为我精心挑选好了。
$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
chromium-browser chromium-browser-l10n chromium-codecs-ffmpeg
3 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 25.1 MB of archives.
After this operation, 5,026 kB of additional disk space will be used.
Do you want to continue [Y/n]?