yes

continuously outputs the specified string. By default it's "y":

yes [string]

For example:

yes FIRE ALARM! Leave the building!

fills the terminal screen with

FIRE ALARM! Leave the building!
FIRE ALARM! Leave the building!
FIRE ALARM! Leave the building!
FIRE ALARM! Leave the building!
FIRE ALARM! Leave the building!
FIRE ALARM! Leave the building!
FIRE ALARM! Leave the building!

You must press CTRL+C to stop it.

The only options are --help and --version.

yum

(Yellowdog Updater Modified) is an interactive, automated update program for rpm-based systems.

yum [options] [cmd] [pkg ...]

While installing or updating packages ~ ensures that all dependencies are satisfied. If no package matches pkg, it’s assumed to be a shell glob and any matches are then installed (updated).

yum list all

list all available and installed packages;

yum list available

list all packages in the repositories available for installation;

yum list updates

list all packages with updates available in the repositories;

yum clean packages

eliminate any cached pkgs from the system (downloaded pkgs are not automatically deleted);

yum clean headers

eliminate all files which ~ uses to determine the remote availability of pkgs; it will force ~ to download all headers at the next run;

yum clean all

this is the combination of previous two;

yum update

update all pkgs that can be udated (condition is: pkg must be installed and update for it must be available);

Commands

install

install the latest version of a package or group of pkgs;

update

if no package name is given, update every currently installed pkg; if one or more pkgs are specified, update only those packages;

check-update

check if any updates are available; if there is nothing suitable, returns exit value 0; otherwise, returns exit value 100 and a list of pkgs to be updated;

remove

remove the specified pkgs and their dependants from the system;

list

list information about available pkgs;

provides

find out which pkg provides some file or feature;

search

find any packages matching the string in the description, summary, packager / package name field of an rpm file;

info

list a description / summary of the available pkgs;

clean

clean up various things which accumulate in the ~ cashe dir over time;

generate-rss

create a rss file containing changelogs for all pkgs in the enabled repositories (by default it lists the most recent only);

Options

-h    --help    --version

-c [file]

use the specified config file (by default /etc/yum.conf);

-C run entirely from cache, do not download or update any headers unless it’s necessary to perform requested action;

-d [n]

set the debugging level (reasonable range is 0..10);

-e [n]

set the error level (the range is 0..10); 0 means print only critical errors; 1 means print all errors;

-R [t]

set the max amount of time (in minutes) ~ will wait before performing a command;

-t be tolerant to the errors on the command line with regard to packages specified (suppress unnecessary error messages);
-y assume "yes" to any questions;

--disablerepo=repoid

disable a specific repository;

--enablerepo=repoid

enable a specific repository, that was disabled in the config file;

--exclude=pkg

exclude a specific package by name or glob from updates on all repositories;

--installroot=root

use an alternative installroot, relative to which all pkgs will be installed;

--obsoletes

(for updates only) signals ~ to include pkg obsoletes in its calculations which is convenient when upgrading to a new distro-version (e.g., from SomeLinux 1.0 to SomeLinux 2.0);

--rss-filename=fname

output rss data for the generate-rss cmd to the specified file;

Though ~ is supposed to access repositories over the Internet, it's also possible to use it locally. Repository is just a directory with rpm pkgs plus metadata, which can be generated by createrepo utility. The procedure is like follows (fedora packages):