5- Managed shared libraries and packages Management Flashcards Preview

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Flashcards in 5- Managed shared libraries and packages Management Deck (19)
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Any shared library file namw will have ... in it

.so (shared object file which is a library)


shared library locations

shared files between system and users
generally found in /lib/, usr/lib, /usr/lib64, /usr/local/lib


static linking to shared libraries

Applications CONTAIN a full copy of the .so aka shared library file.
The contained library has all the characteristics expected by the application.
The library is that it is a fixed version and so doesn't have the updates and fixes of later versions



list of libraries that the application uses

ldd to know different libraries required
Ex : Which sshd --> ldd /usr/sbin/sshd



Updates ld.so.cache file (located in /etc/)

creates the necessary links and cache to the most recent shared libraries found in the directories specified on the command line, in the file /etc/ld.so.conf, and in the trusted directories ( /lib/, usr/lib, /usr/lib64, /usr/local/lib)


what's /etc/ld.so.conf

It holds path settings which point to directories that hold (dynamic) libraries. It's used by ldconfig to create necessary links and cache.
Programs, when dynamicaly compiled, need libraries to run. In general ld.so.conf holds the basic directories where these libs can be found. Sometimes you have to add another line to that file.


aptitude vs synaptic

GUI based applications for Debian package management.


where are the Debian package configuration files?




define the repositories that come with the system, which it means the repositories that will be installed during system installation.


Two type of repositories are defined in source.list

deb repositories: which is a binary repository which will install libraries, application packages, ..etc
deb-src repository it contains the related source code for the packages that identified by deb repository

- Debian/ubuntu use a nick name (trusty used in 16.04 distribution) in url repository to pull information.

- restricted keyword it means a restricted software that it does not require license
- universe that software is not supported it means that it would not get software update.


Command to update system app

apt-get update

- Any changes in repository configuration file required this command.
- This command updates all the repository to get a list of all the packages for each one of the URLs



directory in Ubuntu/Debian where third-party (non Ubuntu or Debian) repositories can be added


How to add a new third-party repository for apt?

create a file in /etc/sources.list.d with the URL, and other qualifiers, then run apt-get update to refresh your local repo cache.


apt-get upgrade

- must be used after apt-get update
- it updates the existing system and any installed software to the newest version that reported from the configuration repository for this distribution.
- to upgrade the system: apt-get dist-upgrade


to remove app

apt-get remove app
- it does not remove config files that has been changed


apt-get purge app

removes the packages and the configuration files


a command to search for a package in a system

apt-cache search app
- This command will show any application that has similar name.


a command to show information about specific package

How to get information about sshd?

apt-cache show app
apt-cache show sshd


a command to show more technical information about thepackage

apt-cache showpkg app
- it show the required dependencies