Introduction
In our earlier articles on package management for Debian bases distributions, we’ve covered dpkg, apt-get, and apt-cache tools. In this article, we will cover the apt tool for managing packages on our Ubuntu 16.04 system. The command line options for apt are very similar to those available with apt-get and apt-cache because apt encompasses features of both these tools into one package management tool. Apt is a front-end tool which works with dpkg in the background to maintain software on the system.
To interact with the apt package manager, we use the apt command along with the appropriate options.
We’ll now take you through some examples to help understand how we use the apt package manager.
Example 1: Update local cache
The system queries online remote and local repositories and maintains a cache of information about packages available in these repositories. This cache could be regarded as an index of available packages in the online repositories. The names and URLs of these online repositories are maintained in /etc/apt/sources.list file.
Given below is a snippet from the file on my local system:
root@linuxnix:~# cat /etc/apt/sources.list | grep -Ev '^#|^$|ec2' deb http://security.ubuntu.com/ubuntu xenial-security main restricted deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted deb http://security.ubuntu.com/ubuntu xenial-security universe deb-src http://security.ubuntu.com/ubuntu xenial-security universe deb http://security.ubuntu.com/ubuntu xenial-security multiverse deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse
We can update that cache using the apt update command. Periodically updating the cache ensures that any new packages or package updates available in the repositories are also updated in the local cache.
root@linuxnix:~# apt update Hit:1 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial InRelease Hit:2 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial-updates InRelease Hit:3 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial-backports InRelease Hit:4 http://security.ubuntu.com/ubuntu xenial-security InRelease Reading package lists... Done Building dependency tree Reading state information... Done All packages are up to date. root@linuxnix:~#
Example 2: System update
To update all packages installed on the system to their latest version, we use the apt upgrade command.
root@linuxnix:~# apt upgrade Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages were automatically installed and are no longer required: libblas-common libblas3 liblinear3 liblua5.2-0 libxslt1.1 linux-aws-headers-4.4.0-1032 linux-headers-4.4.0-1032-aws linux-image-4.4.0-1032-aws lua-lpeg ndiff python-bs4 python-chardet python-html5lib python-lxml python-pkg-resources python-six Use 'apt autoremove' to remove them. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. root@linuxnix:~#
Example 3: Update all packages including the kernel
The apt upgrade command updates all packages on the system for which updates are available except for the Linux kernel.
If you wish to update the Linux kernel as well then use the apt dist-upgrade command as shown below.
root@linuxnix:~# apt dist-upgrade Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages were automatically installed and are no longer required: libblas-common libblas3 liblinear3 liblua5.2-0 libxslt1.1 linux-aws-headers-4.4.0-1032 linux-headers-4.4.0-1032-aws linux-image-4.4.0-1032-aws lua-lpeg ndiff python-bs4 python-chardet python-html5lib python-lxml python-pkg-resources python-six Use 'apt autoremove' to remove them. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. root@linuxnix:~#
Example 4: Search for a package
To search for a package we use the apt search command followed by the package name.
Let’s search for the zsh shell package.
root@linuxnix:~# apt search zsh Sorting... Done Full Text Search... Done csh/xenial 20110502-2.1ubuntu1 amd64 Shell with C-like syntax direnv/xenial 2.7.0-1 amd64 Utility to set directory specific environment variables -----------------------output truncated for brevity zsh-common/xenial 5.1.1-1ubuntu2 all architecture independent files for Zsh -----------------------output truncated for brevity
As you may observe from the output, apt performs a fuzzy match for the package name being searched i.e. it matches complete names, part of the package name and also the package description.
The resulting output shows some information about the matches found like the name, source repository, version and architecture followed by a one-line description of the package in the next line.
Example 5: Get information about a package
We use the apt show command to obtain information about a package.
Let’s display information about the zsh shell we searched for in the previous example.
root@linuxnix:~# apt show zsh Package: zsh Version: 5.1.1-1ubuntu2 Priority: optional Section: shells Origin: Ubuntu Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com> Original-Maintainer: Debian Zsh Maintainers <pkg-zsh-devel@lists.alioth.debian.org> Bugs: https://bugs.launchpad.net/ubuntu/+filebug Installed-Size: 2,023 kB Pre-Depends: dpkg (>= 1.17.14) Depends: zsh-common (= 5.1.1-1ubuntu2), libc6 (>= 2.15), libcap2 (>= 1:2.10), libtinfo5 (>= 6) Recommends: libncursesw5 (>= 6), libpcre3 Suggests: zsh-doc Homepage: http://www.zsh.org/ Supported: 5y Download-Size: 651 kB APT-Sources: http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 Packages Description: shell with lots of features Zsh is a UNIX command interpreter (shell) usable as an interactive login shell and as a shell script command processor. Of the standard shells, zsh most closely resembles ksh but includes many enhancements. Zsh has command-line editing, built-in spelling correction, programmable command completion, shell functions (with autoloading), a history mechanism, and a host of other features.
This command displays a lot of information about the package including it’s installed state, any dependencies required and also details about conflicts with other packages.
Example 6: Install a package
To install a new package we use the apt install command followed by the package name.
Let’s install the zsh shell package we’ve used in our earlier examples to demonstrate.
root@linuxnix:~# apt install zsh Reading package lists... Done Building dependency tree Reading state information... Done The following additional packages will be installed: zsh-common Suggested packages: zsh-doc The following NEW packages will be installed: zsh zsh-common 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 3,822 kB of archives. After this operation, 14.2 MB of additional disk space will be used. Do you want to continue? [Y/n] Y Get:1 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 zsh-common all 5.1.1-1ubuntu2 [3,170 kB] Get:2 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 zsh amd64 5.1.1-1ubuntu2 [651 kB] Fetched 3,822 kB in 1s (3,195 kB/s) Selecting previously unselected package zsh-common. (Reading database ... 108061 files and directories currently installed.) Preparing to unpack .../zsh-common_5.1.1-1ubuntu2_all.deb ... Unpacking zsh-common (5.1.1-1ubuntu2) ... Selecting previously unselected package zsh. Preparing to unpack .../zsh_5.1.1-1ubuntu2_amd64.deb ... Unpacking zsh (5.1.1-1ubuntu2) ... Processing triggers for man-db (2.7.5-1) ... Setting up zsh-common (5.1.1-1ubuntu2) ... Setting up zsh (5.1.1-1ubuntu2) ... update-alternatives: using /bin/zsh5 to provide /bin/zsh (zsh) in auto mode update-alternatives: using /bin/zsh5 to provide /bin/rzsh (rzsh) in auto mode root@linuxnix:~#
If you were to run the apt show command for the zsh shell again you would now see an additional line “APT-Manual-Installed: yes” confirming the status of the package as installed.
Example 7: Remove a package
To remove a package we use the apt remove command followed by the package name.
Let’s demonstrate by removing the zsh shell package we installed in the previous example.
root@linuxnix:~# apt remove zsh Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: libblas-common libblas3 liblinear3 liblua5.2-0 libxslt1.1 linux-aws-headers-4.4.0-1032 linux-headers-4.4.0-1032-aws linux-image-4.4.0-1032-aws lua-lpeg ndiff python-bs4 python-chardet python-html5lib python-lxml python-pkg-resources python-six zsh-common Use 'apt autoremove' to remove them. The following packages will be REMOVED: zsh 0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded. After this operation, 2,023 kB disk space will be freed. Do you want to continue? [Y/n] Y (Reading database ... 109329 files and directories currently installed.) Removing zsh (5.1.1-1ubuntu2) ... root@linuxnix:~#
Example 8: Purge a package
Using apt remove to delete a package removes the package binaries but leaves the configuration files.
To remove the configuration files as well, use the apt purge command followed by the package name.
Note that you can run apt purge command on already removed packages.
We’ll now perform and apt purge on the zsh package
root@linuxnix:~# apt purge zsh Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: libblas-common libblas3 liblinear3 liblua5.2-0 libxslt1.1 linux-aws-headers-4.4.0-1032 linux-headers-4.4.0-1032-aws linux-image-4.4.0-1032-aws lua-lpeg ndiff python-bs4 python-chardet python-html5lib python-lxml python-pkg-resources python-six zsh-common Use 'apt autoremove' to remove them. The following packages will be REMOVED: zsh* 0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded. After this operation, 2,023 kB disk space will be freed. Do you want to continue? [Y/n] Y (Reading database ... 109329 files and directories currently installed.) Removing zsh (5.1.1-1ubuntu2) ... Purging configuration files for zsh (5.1.1-1ubuntu2) ... root@linuxnix:~#
Example 9: Search for specific package name only
The apt search command which we demonstrated earlier performs a regex search for matching package names.
If you’d like to limit the search to the specific package only then use the apt list command.
root@linuxnix:~# apt list zsh Listing... Done zsh/xenial 5.1.1-1ubuntu2 amd64 root@linuxnix:~#
Example 10: List all installed packages
To display a list of all packages currently installed on the system use the following command.
root@linuxnix:~# apt list --installed Listing... Done accountsservice/xenial-updates,now 0.6.40-2ubuntu11.3 amd64 [installed] acl/xenial,now 2.2.52-3 amd64 [installed] acpid/xenial,now 1:2.0.26-1ubuntu2 amd64 [installed] adduser/xenial,now 3.113+nmu3ubuntu4 all [installed] amazon-ssm-agent/now 2.2.93.0-1 amd64 [installed,local] apparmor/xenial-updates,now 2.10.95-0ubuntu2.7 amd64 [installed] apport/xenial-updates,now 2.20.1-0ubuntu2.14 all [installed] apport-symptoms/xenial,now 0.20 all [installed] apt/xenial-updates,now 1.2.24 amd64 [installed] apt-transport-https/xenial-updates,now 1.2.24 amd64 [installed] apt-utils/xenial-updates,now 1.2.24 amd64 [installed] at/xenial,now 3.1.18-2ubuntu1 amd64 [installed] -------------------------------output truncated for brevity
Example 11: List dependencies for a package
To list dependencies for a package use the apt depends command followed by the package name.
root@linuxnix:~# apt depends zsh zsh PreDepends: dpkg (>= 1.17.14) Depends: zsh-common (= 5.1.1-1ubuntu2) Depends: libc6 (>= 2.15) Depends: libcap2 (>= 1:2.10) Depends: libtinfo5 (>= 6) Recommends: libncursesw5 (>= 6) Recommends: libpcre3 Suggests: zsh-doc
Example 12: Download packages without installation
To download a package to the current working directory without installation, use the apt download command followed by the package name.
Let’s download the zsh package.
root@linuxnix:~# apt download zsh Get:1 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 zsh amd64 5.1.1-1ubuntu2 [651 kB] Fetched 651 kB in 0s (17.5 MB/s) downloading as file '/root/zsh_5.1.1-1ubuntu2_amd64.deb' root@linuxnix:~# ls -l zsh_5.1.1-1ubuntu2_amd64.deb -rw-r--r-- 1 root root 651294 Feb 7 2016 zsh_5.1.1-1ubuntu2_amd64.deb root@linuxnix:~#
Although the next three examples that we’re about to demonstrate do not use the apt tool, we decided to include them for a complete feature set representation of the package management features in the Ubuntu operating system.
Example 13: Lock a package
We can prevent a package from being upgraded by Ubuntu by locking it to the currently installed version.
We achieve this by using the apt-mark hold command followed by the package name.
Let’s lock the sudo package to demonstrate.
root@linnuxnix:~# apt-mark hold sudo sudo set on hold.
Example 14: Unlock a package
To unlock a package we use the apt-mark unhold command followed by the package name.
This makes the package available for subsequent updates performed using the apt upgrade command.
We’ll unhold the sudo package now.
root@linnuxnix:~# apt-mark unhold sudo Canceled hold on sudo.
Example 15: View package content
We can use the dpkg -L command or the dpkg -c command to query the files that were installed by a package but to obtain the same information about a package in an internet repository, we need to use the apt-file command.
This is not available by default, so let’s install it first.
root@linnuxnix:~# apt install apt-file Reading package lists... Done Building dependency tree Reading state information... Done linux-image-4.4.0-1032-aws lua-lpeg ndiff python-bs4 python-chardet python-html5lib python-lxml python-pkg-resources python-six zsh-common Use 'apt autoremove' to remove them. The following additional packages will be installed: libapt-pkg-perl libconfig-file-perl libexporter-tiny-perl liblist-moreutils-perl libregexp-assemble-perl The following NEW packages will be installed: apt-file libapt-pkg-perl libconfig-file-perl libexporter-tiny-perl liblist-moreutils-perl libregexp-assemble-perl 0 upgraded, 6 newly installed, 0 to remove and 0 not upgraded. Need to get 270 kB of archives. After this operation, 881 kB of additional disk space will be used. Do you want to continue? [Y/n] y Get:1 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/universe amd64 libconfig-file-perl all 1.50-3 [9,722 B] Get:2 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 libapt-pkg-perl amd64 0.1.29build7 [65.3 kB] Get:3 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 libexporter-tiny-perl all 0.042-1 [28.8 kB] Get:4 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 liblist-moreutils-perl amd64 0.413-1build1 [67.0 kB] Get:5 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/universe amd64 libregexp-assemble-perl all 0.36-1 [77.5 kB] Get:6 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/universe amd64 apt-file all 2.5.5ubuntu1 [21.6 kB] Fetched 270 kB in 2s (102 kB/s) Selecting previously unselected package libconfig-file-perl. (Reading database ... 109281 files and directories currently installed.) Preparing to unpack .../libconfig-file-perl_1.50-3_all.deb ... Unpacking libconfig-file-perl (1.50-3) ... Selecting previously unselected package libapt-pkg-perl. Preparing to unpack .../libapt-pkg-perl_0.1.29build7_amd64.deb ... Unpacking libapt-pkg-perl (0.1.29build7) ... Selecting previously unselected package libexporter-tiny-perl. Preparing to unpack .../libexporter-tiny-perl_0.042-1_all.deb ... Unpacking libexporter-tiny-perl (0.042-1) ... Selecting previously unselected package liblist-moreutils-perl. Preparing to unpack .../liblist-moreutils-perl_0.413-1build1_amd64.deb ... Unpacking liblist-moreutils-perl (0.413-1build1) ... Selecting previously unselected package libregexp-assemble-perl. Preparing to unpack .../libregexp-assemble-perl_0.36-1_all.deb ... Unpacking libregexp-assemble-perl (0.36-1) ... Selecting previously unselected package apt-file. Preparing to unpack .../apt-file_2.5.5ubuntu1_all.deb ... Unpacking apt-file (2.5.5ubuntu1) ... Processing triggers for man-db (2.7.5-1) ... Setting up libconfig-file-perl (1.50-3) ... Setting up libapt-pkg-perl (0.1.29build7) ... Setting up libexporter-tiny-perl (0.042-1) ... Setting up liblist-moreutils-perl (0.413-1build1) ... Setting up libregexp-assemble-perl (0.36-1) ... Setting up apt-file (2.5.5ubuntu1) ... The system-wide cache is empty. You may want to run 'apt-file update' as root to update the cache. You can also run 'apt-file update' as normal user to use a cache in the user's home directory. root@linnuxnix:~#
The apt-file utility also maintains a cache which is empty at initial install.
To update its cache we use the following command:
root@linnuxnix:~# apt-file update Downloading complete file http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu/dists/xenial/Contents-amd64.gz % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 31.7M 100 31.7M 0 0 52.1M 0 --:--:-- --:--:-- --:--:-- 52.0M -------------------------------------------------------------------output truncated for brevity
Now let’s query what files make up the nmap package using the apt-file list command
root@linnuxnix:~# apt-file list nmap libnmap-parser-perl: /usr/share/doc/libnmap-parser-perl/README libnmap-parser-perl: /usr/share/doc/libnmap-parser-perl/changelog.Debian.gz libnmap-parser-perl: /usr/share/doc/libnmap-parser-perl/copyright libnmap-parser-perl: /usr/share/doc/libnmap-parser-perl/examples/nmap2sqlite.pl.gz libnmap-parser-perl: /usr/share/doc/libnmap-parser-perl/examples/scan.pl.gz libnmap-parser-perl: /usr/share/man/man3/Nmap::Parser.3pm.gz libnmap-parser-perl: /usr/share/perl5/Nmap/Parser.pm nmap: /usr/bin/ncat nmap: /usr/bin/nmap nmap: /usr/bin/nping nmap: /usr/share/doc/nmap/3rd-party-licenses.txt.gz -----------------------------------------------------output truncated for brevity
As evident from the above output, the apt-file utility is very useful for obtaining the list of files that would make up a package.
Conclusion
This concludes our exploration of the apt package management tool for Debian/Ubuntu systems.
We encourage you to use the apt package manager over apt-get and apt-cache tools since apt combines the functionality of both utilities into one.
Sahil Suri
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