Books / Linux Notes for Professionals / Chapter 10

Linux Services

In this chapter

List running service on Ubuntu
Systemd Service Management
Diagnosing a problem with a service
Starting and Stopping Services
Getting the status of a service

List running service on Ubuntu

To get a list of the service on your system, you may run:

service --status-all

The output lists the state of services controlled by System V.

The + indicates the service is running, - indicates a stopped service. You can see this by running service SERVICENAME status for a + and - service.

Some services are managed by Upstart. You can check the status of all Upstart services with sudo initctl list. Any service managed by Upstart will also show in the list provided by service --status-all but will be marked with a ?.

ref: https://askubuntu.com/questions/407075/how-to-read-service-status-all-results

Systemd Service Management

Listing Services

systemctl To list running services
systemctl --failed To list failed services

Managing Targets (Similar to Runlevels in SysV)

systemctl get-default To find the default target for your system
systemctl set-default <target-name> To set the default target for your system

Managing services at runtime

systemctl start [service-name] To start a service
systemctl stop [service-name] To stop a service
systemctl restart [service-name] To restart a service
systemctl reload [service-name] To request service to reload its configuration
systemctl status [service-name] To show current status of a service

Managing autostart of services

systemctl is-enabled [service-name] To show whether a service is enabled on system boot
systemctl is-active [service-name] To show whether a service is currently active(running)
systemctl enable [service-name] To enable a service on system boot
systemctl disable [service-name] To disable a service on system boot

Masking services

systemctl mask [service-name] To mask a service (Makes it hard to start a service by mistake)
systemctl unmask [service-name] To unmask a service

Restarting systemd

systemctl daemon-reload

Diagnosing a problem with a service

On systems using systemd, such as Fedora => 15, Ubuntu (Server and Desktop) >= 15.04, and RHEL/CentOS >= 7:

systemctl status [servicename]

where [servicename] is the service in question; for example, systemctl status sshd.

This will show basic status information and any recent errors logged.

You can see further errors with journalctl. For example, journalctl -xe will load the last 1000 logged into a pager (like less ), jumping to the end. You can also use journalctl -f, which will follow log messages as they come in.

To see logs for a particular service, use the -t flag, like this:

journalctl -f -t sshd

Other handy options include -p for priority (-p warnings to see only warnings and above), -b for “since last boot”, and -S for “since” — putting that together, we might do:

journalctl -p err -S yesterday

to see all items logged as errors since yesterday.

If journalctl is not available, or if you are following application error logs which do not use the system journal, the tail command can be used to show the last few lines of a file. A useful flag for tail is -f (for “follow”), which causes tail continue showing data as it gets appended to the file. To see messages from most services on the system:

tail-f/var/log/message

Or, if the service is privileged, and may log sensitive data:

tail-f/var/log/secure

Some services have their own log files, a good example is auditd, the linux auditing daemon, which has its logs stored in /var/log/audit/. If you do not see output from your service in /var/log/messages try looking for service specific logs in /var/log/.

Starting and Stopping Services

On systems that use the System-V style init scripts, such as RHEL/CentOS 6:

service <service> start

service <service> stop

On systems using systemd, such as Ubuntu (Server and Desktop) >= 15.04, and RHEL/CentOS >= 7:

systemctl <service> dnsmasq

systemctl <service> dnsmasq

Getting the status of a service