# Basics of Linux ### Managing software

# Managing software
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1. Script / write your own code
                        2. Download and compile from source code
                        3. Download and install binaries
                        4. Use package manager

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                            <img src="/img/sld-linux-1-managing-sw-01.svg">
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                        # Script / write your own code
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- Stored in your home directory
                          - e.g. `~/bin`
                        - Can be included in your personal `$PATH` variable
                        - Runs only in user space by default
                        - Relies on the software already installed on the operating system

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                        # Download and compile from source code
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- Many open software tools are available from public repositories
                          - Actively maintained projects receive security patches and new features
                          - It is the user's responsibility to update to the latest version
                        - Linux distribution independent
                        - But same restrictions and rules apply as with _"Script / write your own code"_

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                        # Download and install binaries
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- There are distribution independent binaries and distribution dependent binaries
                        - Distribution independent binaries are usually a standalone download of a binary file
                          - Processor architecture (x86, amd64, risc) dependent
                        - Distribution dependent:
                          - Red Hat: `rpm`
                          - Debian: `deb`
                          - Installation usually requires root permissions
                          - Consists of a set of files

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                        # Use package manager
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- Based on binary or source code file formats
                        - In theory, package managers are distribution independent, but in practice there is a _de facto_ manager for each distribution:
                          - Red Hat: `dnf` or `yum`
                          - Debian: `apt-get` or `apt`
                          - SUSE: `zypper`
                          - Arch Linux: `pacman`
                          - Gentoo: Portage / `emerge`
                        - One manager per operating system
                        - Using package manager requires root permissons

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                        # Package manager
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sequenceDiagram
                                note over Client,Server: Add repository URL
                                Client->>Client: edit sources.list file
                                Client->>+Server: Validate repository
                                Server-->>-Client: Repository OK
                                note over Client,Server: Update index
                                Client->>Client: apt-get update
                                Client->>+Server: Get list of available software
                                Server-->>-Client: Index (txt)
                                note over Client,Server: Install software
                                Client->>Client: apt-get upgrade / install
                                Client->>+Server: Ask for binary package(s)
                                Server-->>-Client: Binary package(s)
                                Client->>Client: dpkg -i binary

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                        # Package manager
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- Keeps track of installed software and versions
                        - Commands to easily add, update and remove software
                        - Typical use is to update software from the internet, but offline sources (e.g. CDs) are also supported

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                            <img src="/img/sld-linux-1-managing-sw-02.svg" alt="View of Debian sources.list file in a terminal window.">
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                        # Package manager
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- There are less open software repositories, such as Ubuntu's snap
                        - Some repositories, such as Red Hat's, require also a separate access (paid subscription)
                        - "Any" URL can be added as a source for software
                          - Potential security risk
                          - Operating system trusts and installs software coming from that source

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                        # Beyond package managers
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- Docker containers
                        - Flatpak and AppImage
                        - Python (virtual) environments
                          - Pip, conda, etc.

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Thank you

Joona Tolonen

servicedesk@csc.fi