# Manage software on your AL2 instance
The base distribution of Amazon Linux contains the software packages and utilities that are required for basic server operations.
This information applies to AL2. For information about AL2023, see [Manage packages and operating system updates in AL2023](https://docs.aws.amazon.com/linux/al2023/ug/managing-repos-os-updates.html) in the *Amazon Linux 2023 User Guide*.
It is important to keep software up to date. Many packages in a Linux distribution are updated frequently to fix bugs, add features, and protect against security exploits. For more information, see [Update instance software on your AL2 instance](install-updates.md).
By default, AL2 instances launch with the following repositories enabled:
+ `amzn2-core`
+ `amzn2extra-docker`
While there are many packages available in these repositories that are updated by AWS, there might be a package that you want to install that is contained in another repository. For more information, see [Add repositories on an AL2 instance](add-repositories.md). For help finding and installing packages in enabled repositories, see [Find and install software packages on an AL2 instance](find-install-software.md).
Not all software is available in software packages stored in repositories; some software must be compiled on an instance from its source code. For more information, see [Prepare to compile software on an AL2 instance](compile-software.md).
AL2 instances manage their software using the yum package manager. The yum package manager can install, remove, and update software, as well as manage all of the dependencies for each package.
**Topics**
+ [Update instance software on your AL2 instance](install-updates.md)
+ [Add repositories on an AL2 instance](add-repositories.md)
+ [Find and install software packages on an AL2 instance](find-install-software.md)
+ [Prepare to compile software on an AL2 instance](compile-software.md)
# Update instance software on your AL2 instance
It is important to keep software up to date. Packages in a Linux distribution are updated frequently to fix bugs, add features, and protect against security exploits. When you first launch and connect to an Amazon Linux instance, you might see a message asking you to update software packages for security purposes. This section shows how to update an entire system, or just a single package.
This information applies to AL2. For information about AL2023, see [Manage packages and operating system updates in AL2023](https://docs.aws.amazon.com/linux/al2023/ug/managing-repos-os-updates.html) in the *Amazon Linux 2023 User Guide*.
For information about changes and updates to AL2, see [AL2 release notes](https://docs.aws.amazon.com/AL2/latest/relnotes/relnotes-al2.html).
For information about changes and updates to AL2023, see [AL2023 release notes](https://docs.aws.amazon.com/linux/al2023/release-notes/relnotes.html).
**Important**
If you launched an EC2 instance that uses an Amazon Linux 2 AMI into an IPv6-only subnet, you must connect to the instance and run `sudo amazon-linux-https disable`. This lets your AL2 instance connect to the yum repository in S3 over IPv6 using the http patch service.
**To update all packages on an AL2 instance**
1. (Optional) Start a **screen** session in your shell window. Sometimes you might experience a network interruption that can disconnect the SSH connection to your instance. If this happens during a long software update, it can leave the instance in a recoverable, although confused state. A **screen** session allows you to continue running the update even if your connection is interrupted, and you can reconnect to the session later without problems.
1. Execute the **screen** command to begin the session.
```
[ec2-user ~]$ screen
```
1. If your session is disconnected, log back into your instance and list the available screens.
```
[ec2-user ~]$ screen -ls
There is a screen on:
17793.pts-0.ip-12-34-56-78 (Detached)
1 Socket in /var/run/screen/S-ec2-user.
```
1. Reconnect to the screen using the **screen -r** command and the process ID from the previous command.
```
[ec2-user ~]$ screen -r 17793
```
1. When you are finished using **screen**, use the **exit** command to close the session.
```
[ec2-user ~]$ exit
[screen is terminating]
```
1. Run the **yum update** command. Optionally, you can add the `--security` flag to apply only security updates.
```
[ec2-user ~]$ sudo yum update
```
1. Review the packages listed, enter **y**, and press Enter to accept the updates. Updating all of the packages on a system can take several minutes. The **yum** output shows the status of the update while it is running.
1. (Optional) [Reboot your instance](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-reboot.html) to ensure that you are using the latest packages and libraries from your update; kernel updates are not loaded until a reboot occurs. Updates to any `glibc` libraries should also be followed by a reboot. For updates to packages that control services, it might be sufficient to restart the services to pick up the updates, but a system reboot ensures that all previous package and library updates are complete.
**To update a single package on an AL2 instance**
Use this procedure to update a single package (and its dependencies) and not the entire system.
1. Run the **yum update** command with the name of the package to update.
```
[ec2-user ~]$ sudo yum update openssl
```
1. Review the package information listed, enter **y**, and press Enter to accept the update or updates. Sometimes there will be more than one package listed if there are package dependencies that must be resolved. The **yum** output shows the status of the update while it is running.
1. (Optional) [Reboot your instance](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-reboot.html) to ensure that you are using the latest packages and libraries from your update; kernel updates are not loaded until a reboot occurs. Updates to any `glibc` libraries should also be followed by a reboot. For updates to packages that control services, it might be sufficient to restart the services to pick up the updates, but a system reboot ensures that all previous package and library updates are complete.
# Add repositories on an AL2 instance
This information applies to AL2. For information about AL2023, see [Deterministic upgrades through versioned repositories on AL2023](https://docs.aws.amazon.com/linux/al2023/ug/deterministic-upgrades.html) in the *Amazon Linux 2023 User Guide*.
By default, AL2 instances launch with the following repositories enabled:
+ `amzn2-core`
+ `amzn2extra-docker`
While there are many packages available in these repositories that are updated by Amazon Web Services, there might be a package that you want to install that is contained in another repository.
To install a package from a different repository with **yum**, you need to add the repository information to the `/etc/yum.conf` file or to its own `repository.repo` file in the `/etc/yum.repos.d` directory. You can do this manually, but most yum repositories provide their own `repository.repo` file at their repository URL.
**To determine what yum repositories are already installed**
List the installed yum repositories with the following command:
```
[ec2-user ~]$ yum repolist all
```
The resulting output lists the installed repositories and reports the status of each. Enabled repositories display the number of packages they contain.
**To add a yum repository to /etc/yum.repos.d**
1. Find the location of the `.repo` file. This will vary depending on the repository you are adding. In this example, the `.repo` file is at `https://www.example.com/repository.repo`.
1. Add the repository with the **yum-config-manager** command.
```
[ec2-user ~]$ sudo yum-config-manager --add-repo https://www.example.com/repository.repo
Loaded plugins: priorities, update-motd, upgrade-helper
adding repo from: https://www.example.com/repository.repo
grabbing file https://www.example.com/repository.repo to /etc/yum.repos.d/repository.repo
repository.repo | 4.0 kB 00:00
repo saved to /etc/yum.repos.d/repository.repo
```
After you install a repository, you must enable it as described in the next procedure.
**To enable a yum repository in /etc/yum.repos.d**
Use the **yum-config-manager** command with the `--enable repository` flag. The following command enables the Extra Packages for Enterprise Linux (EPEL) repository from the Fedora project. By default, this repository is present in `/etc/yum.repos.d` on Amazon Linux AMI instances, but it is not enabled.
```
[ec2-user ~]$ sudo yum-config-manager --enable epel
```
For more information, and to download the latest version of this package, see [https://fedoraproject.org/wiki/EPEL](https://fedoraproject.org/wiki/EPEL).
# Find and install software packages on an AL2 instance
You can use a package management tool to find and install software packages. In Amazon Linux 2, the default software package management tool is YUM. In AL2023, the default software package management tool is DNF. For more information, see [Package management tool](https://docs.aws.amazon.com/linux/al2023/ug/package-management.html) in the *Amazon Linux 2023 User Guide*.
## Find software packages on an AL2 instance
You can use the **yum search** command to search the descriptions of packages that are available in your configured repositories. This is especially helpful if you don't know the exact name of the package you want to install. Simply append the keyword search to the command; for multiple word searches, wrap the search query with quotation marks.
```
[ec2-user ~]$ yum search "find"
```
The following is example output.
```
Loaded plugins: extras_suggestions, langpacks, priorities, update-motd
============================== N/S matched: find ===============================
findutils.x86_64 : The GNU versions of find utilities (find and xargs)
gedit-plugin-findinfiles.x86_64 : gedit findinfiles plugin
ocaml-findlib-devel.x86_64 : Development files for ocaml-findlib
perl-File-Find-Rule.noarch : Perl module implementing an alternative interface to File::Find
robotfindskitten.x86_64 : A game/zen simulation. You are robot. Your job is to find kitten.
mlocate.x86_64 : An utility for finding files by name
ocaml-findlib.x86_64 : Objective CAML package manager and build helper
perl-Devel-Cycle.noarch : Find memory cycles in objects
perl-Devel-EnforceEncapsulation.noarch : Find access violations to blessed objects
perl-File-Find-Rule-Perl.noarch : Common rules for searching for Perl things
perl-File-HomeDir.noarch : Find your home and other directories on any platform
perl-IPC-Cmd.noarch : Finding and running system commands made easy
perl-Perl-MinimumVersion.noarch : Find a minimum required version of perl for Perl code
texlive-xesearch.noarch : A string finder for XeTeX
valgrind.x86_64 : Tool for finding memory management bugs in programs
valgrind.i686 : Tool for finding memory management bugs in programs
```
Multiple word search queries in quotation marks only return results that match the exact query. If you don't see the expected package, simplify your search to one keyword and then scan the results. You can also try keyword synonyms to broaden your search.
For more information about packages for AL2, see the following:
+ [AL2 Extras Library](al2-extras.md)
+ [Package repository](ec2.md#package-repository)
## Install software packages on an AL2 instance
In AL2, the yum package management tool searches all of your enabled repositories for different software packages and handles any dependencies in the software installation process. For information about installing software packages in AL2023, see [Managing packages and operating system updates](https://docs.aws.amazon.com/linux/al2023/ug/managing-repos-os-updates.html) in the *Amazon Linux 2023 User Guide*.
**To install a package from a repository**
Use the **yum install *package*** command, replacing *package* with the name of the software to install. For example, to install the **links** text-based web browser, enter the following command.
```
[ec2-user ~]$ sudo yum install links
```
**To install RPM package files that you have downloaded**
You can also use **yum install** to install RPM package files that you have downloaded from the internet. To do this, append the path name of an RPM file to the installation command instead of a repository package name.
```
[ec2-user ~]$ sudo yum install my-package.rpm
```
**To list installed packages**
To view a list of installed packages on your instance, use the following command.
```
[ec2-user ~]$ yum list installed
```
# Prepare to compile software on an AL2 instance
Open-source software is available on the internet that has not been pre-compiled and made available for download from a package repository. You might eventually discover a software package that you need to compile yourself, from its source code. For your system to be able to compile software in AL2 and Amazon Linux, you need to install several development tools, such as **make**, **gcc**, and **autoconf**.
Because software compilation is not a task that every Amazon EC2 instance requires, these tools are not installed by default, but they are available in a package group called "Development Tools" that is easily added to an instance with the **yum groupinstall** command.
```
[ec2-user ~]$ sudo yum groupinstall "Development Tools"
```
Software source code packages are often available for download (from websites such as [https://github.com/](https://github.com/) and [http://sourceforge.net/](https://sourceforge.net/)) as a compressed archive file, called a tarball. These tarballs will usually have the `.tar.gz` file extension. You can decompress these archives with the **tar** command.
```
[ec2-user ~]$ tar -xzf software.tar.gz
```
After you have decompressed and unarchived the source code package, you should look for a `README` or `INSTALL` file in the source code directory that can provide you with further instructions for compiling and installing the source code.
**To retrieve source code for Amazon Linux packages**
Amazon Web Services provides the source code for maintained packages. You can download the source code for any installed packages with the **yumdownloader --source** command.
Run the **yumdownloader --source *package*** command to download the source code for *package*. For example, to download the source code for the `htop` package, enter the following command.
```
[ec2-user ~]$ yumdownloader --source htop
Loaded plugins: priorities, update-motd, upgrade-helper
Enabling amzn-updates-source repository
Enabling amzn-main-source repository
amzn-main-source | 1.9 kB 00:00:00
amzn-updates-source | 1.9 kB 00:00:00
(1/2): amzn-updates-source/latest/primary_db | 52 kB 00:00:00
(2/2): amzn-main-source/latest/primary_db | 734 kB 00:00:00
htop-1.0.1-2.3.amzn1.src.rpm
```
The location of the source RPM is in the directory from which you ran the command.