by When you boot a Linux system, a lot of background tasks are kicked in as part of the booting process, that are called services or daemons. These background tasks run without a user intervention.
In systemd-based distributions, systemd is the first process that starts after the system boots and has a PID of ‘1’. Details of the services are stored in unit files located in the "/usr/lib/systemd" directory.
You can use the systemctl command to control/manage systemd units and commonly used options are to start, stop, restart, mask or reload a daemon or service.
As a Linux system administrator, you may handle many services every day. In this quick article, we will describe how to list all services running under systemd on Linux.
1) Listing Linux Services with systemctl
To see all running services on a Linux system with systemd, use the following command. This will show you each active service’s/Unit’s name, load, sub-state, and description about the running unit.
systemctl list-units --type=service --state=running
1.1) Listing other Unit Types
Similarly, you can see other unit types available as shown below. However, first we need to identify the list of supported units through systemctl command with the '-t' option.
# systemctl -t help Available unit types: service mount swap socket target device automount timer path slice scope
You can list all supported unit types by changing '--type=[UNIT_NAME]' based on your requirement. For example, to list the ‘socket’ unit type, run:
# systemctl list-units --type=socket --state=running
If you want to check all running units at once with systemctl command, add all unit types in curly brackets as shown below:
# systemctl list-units --type={service,mount,swap,socket,target,device,automount,timer,path,slice,scope} --state=running
1.2) Checking all Running Units with systemctl
You can list all running units by filtering the 'running' string with the help of the grep command. The following command lists all types of running units including .service, .target, .socket, .mount, etc.
# systemctl | grep -i running proc-sys-fs-binfmt_misc.automount loaded active running Arbitrary Executable File Formats File System Automount Point acpid.path loaded active running ACPI Events Check cups.path loaded active running CUPS Scheduler init.scope loaded active running System and Service Manager session-2.scope loaded active running Session 2 of User linuxgeek accounts-daemon.service loaded active running Accounts Service acpid.service loaded active running ACPI event daemon avahi-daemon.service loaded active running Avahi mDNS/DNS-SD Stack bluetooth.service loaded active running Bluetooth service colord.service loaded active running Manage, Install and Generate Color Profiles
To count all running units, execute: As per the below output, totally 51 units are running on my system. This running service count may vary for you because it depends on the list of packages installed on the system.
# systemctl | grep -i running | wc -l 51
1.3) Filtering a Specific Service
Use the following command to check if a particular service is loaded and running. For example, to verify that the ‘syslog’ service is loaded and running, run: Similarly, you can check any service you want to list.
# systemctl list-units --type=service --state=running | grep -i syslog rsyslog.service loaded active running System Logging Service
1.4) Checking Status of the Service
The following command can be used to view detailed information about a particular running service. It will display a lot of information like running and loaded status, enabled or not at startup, service unit location, PID of the process, how long the process has been running, memory and CPU usage, etc,.
# systemctl status rsyslog
● rsyslog.service - System Logging Service
Loaded: loaded (/lib/systemd/system/rsyslog.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2023-07-15 22:34:47 IST; 2h 2min ago
TriggeredBy: ● syslog.socket
Docs: man:rsyslogd(8)
man:rsyslog.conf(5)
https://www.rsyslog.com/doc/
Main PID: 824 (rsyslogd)
Tasks: 4 (limit: 18893)
Memory: 4.1M
CPU: 184ms
CGroup: /system.slice/rsyslog.service
└─824 /usr/sbin/rsyslogd -n -iNONE
Jul 15 22:34:47 linuxgeek systemd[1]: Starting System Logging Service...
Jul 15 22:34:47 linuxgeek rsyslogd[824]: imuxsock: Acquired UNIX socket '/run/systemd/journal/syslog' (fd 3) from systemd. [v8.2112.0]
Jul 15 22:34:47 linuxgeek rsyslogd[824]: rsyslogd's groupid changed to 110
Jul 15 22:34:47 linuxgeek rsyslogd[824]: rsyslogd's userid changed to 104
Jul 15 22:34:47 linuxgeek rsyslogd[824]: [origin software="rsyslogd" swVersion="8.2112.0" x-pid="824" x-info="https://www.rsyslog.com"] start
Jul 15 22:34:47 linuxgeek systemd[1]: Started System Logging Service.
Jul 16 00:00:02 linuxgeek systemd[1]: rsyslog.service: Sent signal SIGHUP to main process 824 (rsyslogd) on client request.
Jul 16 00:10:02 linuxgeek rsyslogd[824]: [origin software="rsyslogd" swVersion="8.2112.0" x-pid="824" x-info="https://www.rsyslog.com"] rsyslogd was HUPed
Conclusion
This article showed you how to use the systemctl commands to list all running services on Linux, including various options that show more information about a running service.
