document general centos 7 administration

[picatz]

Like what package manager, how to start and stop services with systemd. Tips and tricks.

[malwaremily]

Package Manager

YUM - Yellowdog Updater, Modified

Search through available packages: yum search PACKAGE_NAME

"yum search looks at the following metadata fields: name, summary, description, url."

You can list multiple terms and yum search will list relevant packages by term combination and relevance. yum search PACKAGE_NAME PACKAGE_NAME ...

You can get more information about a package: yum info PACKAGE_NAME

Install a package: sudo yum install PACKAGE_NAME

View installed packages: yum list installed

Remove a package: sudo yum remove PACKAGE_NAME

Clear yum cache: yum clean all "During its normal use yum creates a cache of metadata and packages. This cache can take up a lot of space. The yum clean command allows you to clean up these files. All the files yum clean will act on are normally stored in /var/cache/yum."

Examples:

yum search python rsync ssh yum info rdiff-backup sudo yum install rdiff-backup sudo yum remove rdiff-backup

Sources: https://wiki.centos.org/PackageManagement/Yum http://yum.baseurl.org/wiki/YumCommands

[malwaremily]

systemd & systemctl

• systemd - a system and service manager for Linux operating systems.
• systemctl - used to introspect and control the state of the systemd system and service manager.
• systemd-analyze - used to determine system boot-up performance statistics and retrieve other state and tracing information from the system and service manager.

Starting and Stopping Services

 start service   - `sudo systemctl start service`
 stop service    - `sudo systemctl stop service`
 restart service - `sudo systemctl reload-or-restart service` 

Running Services at Boot

sudo systemctl enable application.service

"This command creates a symoblic link from the system's copy of the service file (typically found in /lib/systemd/system or /etc/systemd/system) into the location on disk where systemd looks for autostart files (typically /etc/systemd/system/some_target.target.wants)"

To disable a service from running automatically

sudo systemctl disable application.service

This removes the symbolic link that indicated the service should be started automatically.

Checking the Status of Services

systemctl status application

This will provide you with information like service state, PID, memory, the cgroup hierarchy, and the first few log lines.

You can also check specific states:

• Active: systemctl is-active application

• Failed: systemctl is-failed application

• Enabled: systemctl is-enabled application

• List Current Units: systemctl or systemctl list-units

• List All Units: systemctl list-units --all

• List Units with a specific state: `systemctl list-units --all --state=active

• List only service units: systemctl list-units --type=service

Sources and more information: https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units https://en.wikipedia.org/wiki/Systemd