From a008b109aa7da7051f42c3a3d43c1daed4dc8088 Mon Sep 17 00:00:00 2001 From: DarkSun Date: Fri, 30 Oct 2020 05:01:42 +0800 Subject: [PATCH] =?UTF-8?q?=E9=80=89=E9=A2=98[tech]:=2020201030=20How=20to?= =?UTF-8?q?=20Use=20apt-cache=20Command=20in=20Debian,=20Ubuntu=20and=20Ot?= =?UTF-8?q?her=20Linux=20Distributions?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit sources/tech/20201030 How to Use apt-cache Command in Debian, Ubuntu and Other Linux Distributions.md --- ...n, Ubuntu and Other Linux Distributions.md | 167 ++++++++++++++++++ 1 file changed, 167 insertions(+) create mode 100644 sources/tech/20201030 How to Use apt-cache Command in Debian, Ubuntu and Other Linux Distributions.md diff --git a/sources/tech/20201030 How to Use apt-cache Command in Debian, Ubuntu and Other Linux Distributions.md b/sources/tech/20201030 How to Use apt-cache Command in Debian, Ubuntu and Other Linux Distributions.md new file mode 100644 index 0000000000..23b314319b --- /dev/null +++ b/sources/tech/20201030 How to Use apt-cache Command in Debian, Ubuntu and Other Linux Distributions.md @@ -0,0 +1,167 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (How to Use apt-cache Command in Debian, Ubuntu and Other Linux Distributions) +[#]: via: (https://itsfoss.com/apt-cache-command/) +[#]: author: (Abhishek Prakash https://itsfoss.com/author/abhishek/) + +How to Use apt-cache Command in Debian, Ubuntu and Other Linux Distributions +====== + +_**With apt-cache command, you can search for package details in the local APT cache. Learn to use apt-cache command in this tutorial.**_ + +### What is apt-cache command used for? + +The [apt][1] [package manager][2] works on a local cache of package metadata. The metadata usually consists information like package name, version, description, dependencies, its repository and developers. With the apt-cache command, you can query this local APT cache and get relevant information. + +You can search for the availability of a package, its version number, its dependencies among other things. I’ll show you how to use the apt-cache command with examples. + +The **location of APT cache** is /var/lib/apt/lists/ directory. Which repository metadata to cache depends on the repositories added in your source list in the /etc/apt/sources.list file and additional repository files located in ls /etc/apt/sources.list.d directory. + +Surprisingly, apt-cache doesn’t clear the APT cache. For that you’ll have to [use the apt-get clean command][3]. + +Needless to say, the APT packaging system is used on Debian and Debian-based Linux distributions like Ubuntu, Linux Mint, elementary OS etc. You cannot use it on Arch or Fedora. + +### Using apt-cache command + +![][4] + +Like any other Linux command, there are several options available with apt-cache and you can always refer to its man page to read about them. + +However, you probably won’t need to use all of them. This is why I am going to show you only the most common and useful examples of the apt-cache command in this tutorial. + +Always update + +It is always a good idea to update the local APT cache to sync it with the remote repositories. How do you do that? You use the command: + +**sudo apt update** + +#### Search for packages + +The most common use of apt-cache command is for finding package. You can use a regex pattern to search for a package in the local APT cache. + +``` +apt-cache search package_name +``` + +By default, it looks for the search term in both the name and description of the package. It shows the matching package along with its short description in alphabetical order. + +![][5] + +You can narrow down your search to look for the search term in package names only. + +``` +apt-cache search --names-only package_name +``` + +![][6] + +If you want complete details of all the matched packages, you may use the `--full` flag. It can also be used with `--names-only` flag. + +![][7] + +#### Get detailed package information + +If you know the exact package name (or if you have manged to find it with the search), you can get the detailed metadata information on the package. + +``` +apt-cache show package_name +``` + +![][8] + +You can see all kind of details in the package metadata like name, version, developer, maintainer, repository, short and long description, package size and even checksum. + +There is another option showpkg that displays information about the package name, version and its forward and reverse dependencies. + +``` +apt-cache showpkg package_name +``` + +#### apt-cache policy + +This is one of the rarely used option of apt-cache command. The policy options helps you debug the issue related to the [preference file][9]. + +If you specify the package name, it will show whether the package is installed, which version is available from which repository and its priority. + +![][10] + +By default, each installed package version has a priority of 100 and a non-installed package has a priority of 500. The same package may have more than one version with a different priority. APT installs the version with higher priority unless the installed version is newer. + +If this doesn’t make sense, it’s okay. It will be extremely rare for a regular Linux user to dwell this deep into package management. + +#### Check dependencies and reverse dependencies of a package + +You can [check the dependencies of a package][11] before (or even after) installing it. It also shows all the possible packages that can fulfill the dependency. + +``` +apt-cache depends package +``` + +![][12] + +You may also check which packages are dependent on a certain package by checking the reverse dependencies with apt-cahce. + +![][13] + +Frankly, I was also surprised to see that a DevOps tool like Ansible has a dependency on a [funny Linux command like Cowsay][14]. I think it’s perhaps because after [installing Ansible][15], it displays some message on the nodes. + +#### Check unmet dependencies + +You may get troubled with [unmet dependencies issue in Ubuntu][16] or other Linux. The apt-cache command provides option to check all the unmet dependencies of various available packages on your system. + +``` +apt-cache unmet +``` + +![][17] + +**Conclusion** + +You can list all available packages with the apt-cache command. The output would be huge, so I suggest combining it with [wc command][18] to get a total number of available packages like this: + +``` +apt-cache pkgnames | wc -l +``` + +Did you notice that you don’t need to be [root user][19] for using apt-cache command? + +The newer [apt command][20] has a few options available to match the features of apt-cache command. Since apt is new, apt-get and its associated commands like apt-cache are still preferred to be used in scripts. + +I hope you find this tutorial helpful. If you have questions about any point discussed above or suggestion to improve it, please let me know in the comments. + +-------------------------------------------------------------------------------- + +via: https://itsfoss.com/apt-cache-command/ + +作者：[Abhishek Prakash][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://itsfoss.com/author/abhishek/ +[b]: https://github.com/lujun9972 +[1]: https://wiki.debian.org/Apt +[2]: https://itsfoss.com/package-manager/ +[3]: https://itsfoss.com/clear-apt-cache/ +[4]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-command.png?resize=800%2C450&ssl=1 +[5]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-search.png?resize=759%2C437&ssl=1 +[6]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-search-names-only.png?resize=759%2C209&ssl=1 +[7]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-show-full.png?resize=759%2C722&ssl=1 +[8]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-show-pkgname.png?resize=800%2C795&ssl=1 +[9]: https://debian-handbook.info/browse/stable/sect.apt-get.html#sect.apt.priorities +[10]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-policy.png?resize=795%2C456&ssl=1 +[11]: https://itsfoss.com/check-dependencies-package-ubuntu/ +[12]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-dependency-check.png?resize=768%2C304&ssl=1 +[13]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-reverse-dependency.png?resize=768%2C304&ssl=1 +[14]: https://itsfoss.com/funny-linux-commands/ +[15]: https://linuxhandbook.com/install-ansible-linux/ +[16]: https://itsfoss.com/held-broken-packages-error/ +[17]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2020/10/apt-cache-unmet.png?resize=759%2C399&ssl=1 +[18]: https://linuxhandbook.com/wc-command/ +[19]: https://itsfoss.com/root-user-ubuntu/ +[20]: https://itsfoss.com/apt-command-guide/