> For the complete documentation index, see [llms.txt](https://predator-os.gitbook.io/predator-os-beginner-guide-book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://predator-os.gitbook.io/predator-os-beginner-guide-book/chapter-8.md).
# Chapter 8
### Chapter 8
### Post installation
### After the First Boot
### Maintenance and Updates: The APT Tools
APT is the abbreviation for Advanced Packaging Tool**.** What makes this program **“**advanced**”** is its approach to packages**.** It does not simply evaluate them individually**,** but it considers them as a whole and produces the best possible combination of packages depending on what is available and compatible according to dependencies**.**
You can also update Predator**-**OS using the terminal**.**
Press CTRL**+**ALT**+**T to bring up a Terminal window**.**
Then type the followings command**:**
**$**sudo apt update
Or
**$**up
### Mange the sources.list
A first apt upgrade **(**a command used to automatically update installed programs**)** is generally required**,** especially for possible security updates issued since the release of the latest PredatorOS stable version**.**
Befor updating and upgrading the Predator**-**OS**:**
The Predator**-**OS used the full repository of Debian stable 20**.**04 by default**.**you can see the list of repositories in the following path**:**
**/etc/apt/sources.list**
Each active line in the **/etc/apt/sources.list** file represents a package source **(**repository**)** and is made of at least three parts separated by spaces**.**
You can manage the repositories by adding or removing lines**.** sources**.**list management by GUI tools**:**
method1 **:**you can manage the repositories by typing the following command**:**
**$**sudo software**-**properties**-**qt
method2**:** you can manage the repositories by Synaptic tool**.**
Debian stable sources list in Predator**-**OS
\##Debian 12.5 bookworm version
deb bookworm non-free-firmware non-free contrib main
deb-src bookworm non-free-firmware non-free contrib main
deb bookworm-security non-free-firmware non-free contrib main
deb-src bookworm-security non-free-firmware non-free contrib main
deb bookworm-updates non-free-firmware non-free contrib main
deb-src bookworm-updates main contrib non-free non-free-firmware
deb bookworm-proposed-updates contrib main non-free non-free-firmware
deb-src bookworm-proposed-updates contrib main non-free non-free-firmware
**Own Predator-os source list**
deb \[arch=amd64] ./
### Upgrading the System
### Apt or apt-get
APT is a vast project**,** whose original plans included a graphical interface**.** It is based on a library which contains the core application**,** and **apt-get** is the first front end — command**-**line based — which was developed within the project**.** **apt** is a second command**-**line based front end provided by APT which overcomes some design mistakes of **apt-get.**
Both tools are built on top of the same library and are thus very close**,** but the default behavior of **apt** has been improved for interactive use and to actually do what most users expect**.** The APT developers reserve the right to change the public interface of this tool to further improve it**.** Conversely**,** the public interface of **apt-get** is well defined and will not change in any backwards incompatible way**.** It is thus the tool that you want to use when you need to script package installation requests**.**
Numerous other graphical interfaces then appeared as external projects**:** **synaptic,** **aptitude** **(**which includes both a text mode interface and a graphical one — even if not complete yet**),** **wajig,** etc**.** The most recommended interface**,** **apt,** is the one that we will use in the examples given in this section**.** Note**,** however**,** that **apt-get** and **aptitude** have a very similar command line syntax**.** When there are major differences between these three commands**,** these will be detailed**.**
Type in**:**
sudo apt update
or use pre**-**definded alias command**:**
**$**up
You will be prompted to enter your login password**.**
### System Upgrade
Regular upgrades are recommended**,** because they include the latest security updates**.** To upgrade**,** use **apt upgrade,** **apt-get upgrade** or **aptitude safeupgrade** **(**of course after **apt update).** This command looks for installed packages which can be upgraded without removing any packages**.** In other words**,** the goal is to ensure the least intrusive upgrade possible**.** **apt-get** is slightly more demanding than **aptitude** or **apt** because it will refuse to install packages which were not installed beforehand**.**
**apt** will generally select the most recent version number **(**except for packages from Experimental and stable**-**backports**,** which are ignored by default whatever their version number**).**
To tell **apt** to use a specific distribution when searching for upgraded packages**,** you need to use the **-t** or **--target-release** option**,** followed by the name of the distribution you want**.** To avoid specifying this option every time you use **apt.** For more important upgrades**,** such as the change from one major version to the next**,** you need to use **apt full-upgrade.** With this instruction**,** **apt** will complete the upgrade even if it has to remove some obsolete packages or install new dependencies**.**
Unlike **apt** and **aptitude,** **apt-get** does not know the **full-upgrade** command**.** Instead**,** you should use **apt-get dist-upgrade** **(“**distribution upgrade**”),** the historical and well**-**known command that **apt** and **aptitude** also except for the convenience of users who got used to it**.** The results of these operations are logged into **/var/log/apt/history.log** and **/var/log/apt/term.log,** whereas **dpkg** keeps its log in a file called **/var/log/dpkg.log.**
This will check for updates and tell you if there are any that need applying**.** To apply any updates type**:**
sudo apt dist**-**upgrade
or use pre**-**definded alias command**:**
**$**ug
### Unattended Upgrades unattended-upgrades
The purpose of[ unattended**-**upgrades ](https://packages.debian.org/unattended-upgrades)is to keep the computer current with the latest security **(**and other**)** updates automatically**.**
If you plan to use it**,** you should have some means to monitor your systems such as installing the[ apt**-**listchanges ](https://packages.debian.org/apt-listchanges)package and configuring it to send you emails about updates**.** And there is always **/**var**/**log**/**dpkg**.**log**,** or the files in **/**var**/**log**/**unattendedupgrades**/.**
Linux server security is of critical importance to sysadmins**.** One central part of keeping Linux servers secure is by installing security updates promptly**.** Too often**,** there are compromised servers on the internet due to pending security updates waiting for a manual update**.** On both Debian stable and Debian**,** the unattended-upgrades package can be configured to perform unattended**-**upgrades to install updated packages and security updates automatically**.**
Remember**,** you will want to monitor updates and changes to your Linux server over time**.** You can monitor via **/var/log/dpkg.log** or read the log files in **/var/log/unattended-upgrades/.** You can also monitor changes by installing the[ apt**-**listchanges ](https://manpages.debian.org/buster/apt-listchanges/apt-listchanges.1.en.html)package **(**optional**).**
sudo apt install apt**-**listchanges
apt**-**get install unattended**-**upgrades apt**-**listchanges sudo dpkg**-**reconfigure unattended**-**upgrades he apt**-**listchanges can be configured to send emails about update changes**.** apt**-**listchanges is a tool to show what has been changed in a new version of a Debian package compared to the version currently installed on the system**.** It does this by extracting the relevant entries from the NEWS**.**Debian and changelog\[**.**Debian] files**,** usually found in **/**usr**/**share**/**doc**/***package***,** from Debian package archives**.** On both Debian and Debian stable**,** as Debian stable is a derivative of Debian**.**
### The apt-cache Command
The **apt-cache** command can display much of the information stored in APT**’**s internal database**.** This information is a sort of cache since it is gathered from the different sources listed in the **sources.list** file**.** This happens during the **apt update** operation**.**
Configuration Options
Besides the configuration elements already mentioned**,** it is possible to configure certain aspects of APT by adding directives in a file of
#### the /etc/apt/apt.conf.d/ directory or /etc/apt/apt.conf itself
### Installing Additional Software
The installed packages correspond to the profiles selected during installation**,** but not necessarily to the use that will actually be made of the machine**.** As such**,** you might want to use a package management tool to refine the selection of installed packages**.** The two most frequently used tools are apt **(**accessible from the command line**)** and synaptic **(“**Synaptic Package Manager**”** in the menus**).**
### Manipulating Packages with dpkg:
dpkg is the base command for handling Debian packages on the system**.** If you have **.**deb packages**,** it is dpkg that allows installation or analysis of their contents**.** it knows what is installed on the system**,** and whatever it is given on the command line**,** but knows nothing of the other available packages**.** As such**,** it will fail if a dependency is not met**.** Tools such as apt and aptitude**,** on the contrary**,** will create a list of dependencies to install everything as automatically as possible**.** Installing Packages dpkg is**,** above all**,** the tool for installing an already available Debian package **(**because it does not download anything**).** To do this**,** we use its **-**i or **--**install option**.**
**$**sudo dpkg **-**i myfile**.**deb
### Frontends: aptitude, synaptic
APT is a C**++** program whose code mainly resides in the **libapt-pkg** shared library**.** Using a shared library facilitates the creation of user interfaces **(**frontends**),** since the code contained in the library can easily be reused**.** Historically**,** **apt-get** was only designed as a test frontend for **libapt-pkg** but its success tends to obscure this fact**.** aptitude
**aptitude** is an interactive program that can be used in semi**-**graphical mode on the console**.** You can browse the list of installed and available packages**,** look up all the available information**,** and select packages to install or remove**.** The program is designed specifically to be used by administrators, so that its default behaviors are designed to be much more intelligent than **apt-get’**s and its interface much easier to understand**.**
### The aptitude package manager
When it starts**,** **aptitude** shows a list of packages sorted by state **(**installed**,** noninstalled**,** or installed but not available on the mirrors — other sections display tasks**,** virtual packages**,** and new packages that appeared recently on mirrors**).** To facilitate thematic browsing other views are available**.** In all cases**,** **aptitude** displays a list combining categories and packages on the screen**.** Categories are organized through a tree structure**,** whose branches can respectively be unfolded or closed with the **Enter,** **\[** and **]** keys**.** **+** should be used to mark a package for installation**,** **-** to mark it for removal and **\_** to purge it **(**note that these keys can also be used for categories**,** in which case the corresponding actions will be applied to all the packages of the category**).** **u** updates the lists of available packages and **Shift+u** prepares a global system upgrade**.** **g** switches to a summary view of the requested changes **(**and typing **g** again will apply the changes**),** and **q** quits the current view**.** If you are in the initial view**,** this will effectively close **aptitude.**
**Synaptic**
**synaptic** is a graphical package manager which features a clean and efficient graphical interface based on GTK**+/**GNOME**.** Its many ready**-**to**-**use filters give fast access to newly available packages**,** installed packages**,** upgradable packages**,** obsolete packages and so on**.** If you browse through these lists**,** you can select the operations to be done on the packages **(**install**,** upgrade**,** remove**,** purge**);** these operations are not performed immediately**,** but put into a task list**.** A single click on a button then validates the operations**,** and they are performed in one go**.**
**synaptic package manager**
### Checking Package Authenticity
Security is very important for administrators**.** Accordingly**,** they need to ensure that they only install packages that are guaranteed with no tampering on the way**.** A computer cracker could try to add malicious code to an otherwise legitimate package**.** Such a package**,** if installed**,** could do anything the cracker designed it to do**,** including for instance disclosing passwords or confidential information**.**
APT needs a set of trusted GnuPG public keys to verify signatures in the InRelease and Release**.**gpg files available on the mirrors**.** It gets them from files in **/**etc**/**apt**/**trusted**.**gpg**.**d**/** and from the **/**etc**/**apt**/**trusted**.**gpg keyring **(**managed by the apt**-**key command**).**
**#** ls **/**etc**/**apt**/**trusted**.**gpg**.**d**/**
