If you are using the current version of Cumulus Linux, the content on this page may not be up to date. The current version of the documentation is available here. If you are redirected to the main page of the user guide, then this page may have been renamed; please search for it there.

Services and Daemons in Cumulus Linux

Services (also known as daemons) and processes are at the heart of how a Linux system functions. Most of the time, a service takes care of itself; you just enable and start it, then let it run. However, because a Cumulus Linux switch is a Linux system, you can dig deeper if you like. Services can start multiple processes as they run. Services are important to monitor on a Cumulus Linux switch.

You manage services in Cumulus Linux to identify all active or stopped services and the boot time state of a specific service, disable or enable a specific service, and identify active listener ports.

systemd and the systemctl Command

You manage services that use systemd with the systemctl command.

Command OptionsDescription
statusReturns the status of the specified service.
startStarts the service.
stopStops the service.
restartStops, then starts the service, all the while maintaining state. If there are dependent services or services that mark the restarted service as Required, the other services also restart. For example, running systemctl restart frr.service restarts any of the routing protocol services that you enable and that are running, such as bgpd or ospfd.
reloadReloads the configuration for the service.
enableEnables the service to start when the system boots, but does not start it unless you use the systemctl start SERVICENAME.service command or reboot the switch.
disableDisables the service, but does not stop it unless you use the systemctl stop SERVICENAME.service command or reboot the switch. You can start or stop a disabled service.
reenableDisables, then enables a service. Run this command so that any new Wants or WantedBy lines create the symlinks necessary for ordering. This does not affect on other services.

You do not need to interact with the services directly using these commands. If a critical service crashes or encounters an error, systemd restarts it automatically. systemd is the caretaker of services in modern Linux systems and responsible for starting all the necessary services at boot time.

The following example restarts the networking service:

cumulus@switch:~$ sudo systemctl restart networking.service

The following example shows all running services:

cumulus@switch:~$ sudo systemctl status
● switch
    State: running
      Jobs: 0 queued
    Failed: 0 units
    Since: Thu 2019-01-10 00:19:34 UTC; 23h ago
    CGroup: /
            │ └─1 /sbin/init
              │ └─234 /usr/sbin/haveged --Foreground --verbose=1 -w 1024
              │ ├─  658 /bin/bash /usr/lib/cumulus/sysmonitor
              │ └─26543 sleep 60
              │ └─218 /lib/systemd/systemd-udevd
              │ └─ntp@mgmt.service
              │   └─vrf
              │     └─mgmt
              │       └─12108 /usr/sbin/ntpd -n -u ntp:ntp -g
              │ └─274 /usr/sbin/cron -f -L 38
              │ └─serial-getty@ttyS0.service
              │   └─745 /sbin/agetty -o -p -- \u --keep-baud 115200,38400,9600 ttyS0 vt220
              │ ├─332 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
              │ └─333 nginx: worker process
              │ └─235 /sbin/auditd
              │ └─275 /usr/sbin/rasdaemon -f -r
              │ └─11443 /usr/bin/python /usr/sbin/clagd --daemon peerlink.4094 44:39:39:ff:40:9
              --priority 100 --vxlanAnycas
              │ └─430 /usr/sbin/switchd -vx

Add the service name after the systemctl argument.

Ensure a Service Starts after Multiple Restarts

By default, systemd tries to restart a particular service only a certain number of times within a given interval before the service fails to start. The settings StartLimitInterval (which defaults to 10 seconds) and StartBurstLimit (which defaults to 5 attempts) are in the service script; however, certain services override these defaults, sometimes with much longer times. For example, switchd.service sets StartLimitInterval=10m and StartBurstLimit=3; therefore, if you restart switchd more than three times in ten minutes, it does not start.

When the restart fails for this reason, you see a message similar to the following:

Job for switchd.service failed. See 'systemctl status switchd.service' and 'journalctl -xn' for details.

systemctl status switchd.service shows output similar to:

Active: failed (Result: start-limit) since Thu 2016-04-07 21:55:14 UTC; 15s ago

To clear this error, run systemctl reset-failed switchd.service. If you know you are going to restart frequently (multiple times within the StartLimitInterval), you can run the same command before you issue the restart request. This also applies to stop followed by start.

Keep systemd Services from Hanging after Starting

If you start, restart, or reload a systemd service that you can start from another systemd service, you must use the --no-block option with systemctl.

Identify Active Listener Ports for IPv4 and IPv6

You can identify the active listener ports under both IPv4 and IPv6 using the netstat command:

cumulus@switch:~$ netstat -nlp --inet --inet6
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0    *               LISTEN      444/dnsmasq
tcp        0      0    *               LISTEN      874/sshd
tcp6       0      0 :::53                   :::*                    LISTEN      444/dnsmasq
tcp6       0      0 :::22                   :::*                    LISTEN      874/sshd
udp        0      0 *                           839/dhclient
udp        0      0    *                           444/dnsmasq
udp        0      0    *                           839/dhclient
udp        0      0*                           907/ntpd
udp        0      0 *                           907/ntpd
udp        0      0   *                           907/ntpd
udp        0      0  *                           909/ptmd
udp        0      0  *                           909/ptmd
udp        0      0  *                           909/ptmd
udp6       0      0 :::58352                :::*                                839/dhclient
udp6       0      0 :::53                   :::*                                444/dnsmasq
udp6       0      0 fe80::a200:ff:fe00::123 :::*                                907/ntpd
udp6       0      0 ::1:123                 :::*                                907/ntpd
udp6       0      0 :::123                  :::*                                907/ntpd
udp6       0      0 :::4784                 :::*                                909/ptmd
udp6       0      0 :::3784                 :::*                                909/ptmd

Identify Active or Stopped Services

To see active or stopped services, run the cl-service-summary command:

cumulus@switch:~$ cl-service-summary
Service cron               enabled    active   
Service ssh                enabled    active   
Service rsyslog            enabled    active   
Service asic-monitor       enabled    inactive 
Service clagd              disabled   active   
Service cumulus-poe                   inactive 
Service lldpd              enabled    active   
Service mstpd              enabled    active   
Service neighmgrd          enabled    active   
Service netd               enabled    active   
Service netq-agent         disabled   inactive 
Service ntp                disabled   inactive 
Service portwd             enabled    inactive 
Service ptmd               enabled    active   
Service pwmd               enabled    active   
Service smond              enabled    active   
Service switchd            enabled    active   
Service sysmonitor         enabled    active   
Service vxrd                          inactive 
Service vxsnd                         inactive 
Service rdnbrd             disabled   inactive 
Service frr                enabled    active   
Service ntp@mgmt           disabled   inactive 
Service ntp@ntp            disabled   inactive

You can also run the systemctl list-unit-files --type service command to list all services on the switch and to see their status:

cumulus@switch:~$ systemctl list-unit-files --type service
UNIT FILE                                  STATE           VENDOR PRESET
aclinit.service                            enabled         enabled      
acltool.service                            enabled         enabled      
acpid.service                              disabled        enabled      
air-agent@.service                         indirect        enabled      
apt-daily-upgrade.service                  static          -            
apt-daily.service                          static          -            
asic-monitor.service                       enabled         enabled      
atftpd.service                             generated       -            
auditd.service                             enabled         enabled      
autovt@.service                            alias           -            
blk-availability.service                   enabled         enabled      
bmcd.service                               disabled        enabled      
bootlog.service                            enabled         enabled      
cl-system-services.service                 enabled         enabled      
clagd.service                              disabled        enabled      
clagd_rebootNotifier.service               disabled        enabled      
console-getty.service                      disabled        disabled     
console-setup.service                      enabled         enabled      
container-getty@.service                   static          -            
containerd.service                         disabled        enabled      
cron.service                               enabled         enabled      
cryptdisks-early.service                   masked          enabled      
cryptdisks.service                         masked          enabled      
csmgrd.service                             enabled         enabled      
cumulus-aclcheck.service                   static          -            
cumulus-cleanup-health_check.service       static          -            
cumulus-cleanup-lttng_traces.service       static          -            
cumulus-core.service                       static          -

Identify Essential Services

To identify which services must run when the switch boots:

cumulus@switch:~$ systemctl list-dependencies --before basic.target

To identify which services you need for networking:

cumulus@switch:~$ systemctl list-dependencies --after network.target

To identify the services needed for a multi-user environment, run:

cumulus@switch:~$ systemctl list-dependencies --before multi-user.target

 ●  ├─bootlog.service

Important Services

The following table lists the most important services in Cumulus Linux.

Service NameDescriptionAffects Forwarding?
switchdHardware abstraction daemon. Synchronizes the kernel with the ASIC.YES
sx_sdkInterfaces with the Spectrum ASIC. Only on Spectrum switches.YES
frrFRR. Handles routing protocols. There are separate processes for each routing protocol, such as bgpd and ospfd.YES if routing
clagdCumulus link aggregation daemon. Handles MLAG.YES if using MLAG
neighmgrdKeeps neighbor entries refreshed, snoops on ARP and ND packets if ARP suppression is on, and refreshes VRR MAC addresses.YES
mstpdSpanning tree protocol daemon.YES if using layer 2
ptmdPrescriptive Topology Manager. Verifies cabling based on LLDP output. Also sets up BFD sessions.YES if using BFD
nvuedHandles the NVUE object model.NO
rsyslogHandles logging of syslog messages.NO
ntpNetwork time protocol.NO
ledmgrdLED manager. Reads the state of system LEDs.NO
sysmonitorWatches and logs critical system load (free memory, disk, CPU).NO
lldpdHandles Tx/Rx of LLDP information.NO
smondReads platform sensors and fan information from pwmd.NO
pwmdReads and sets fan speeds.NO