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Managing Application Daemons

You manage application daemons (services) in Cumulus Linux in the following ways:

  • Identifying active listener ports
  • Identifying daemons currently active or stopped
  • Identifying boot time state of a specific daemon
  • Disabling or enabling a specific daemon

Using systemd and the systemctl Command

In general, you manage services using systemd via the systemctl command. You use it with any service on the switch to start/stop/restart/reload/enable/disable/reenable or get the status of the service.

cumulus@switch:~$ sudo systemctl start | stop | restart | status | reload | enable | disable | reenable SERVICENAME.service

For example to restart networking, run the command:

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

Unlike the service command in Debian Wheezy, the service name is written after the systemctl subcommand, not before it.

Understanding the systemctl Subcommands

systemctl has a number of subcommands that perform a specific operation on a given daemon.

  • status: Returns the status of the specified daemon.
  • start: Starts the daemon.
  • stop: Stops the daemon.
  • restart: Stops, then starts the daemon, all the while maintaining state. So if there are dependent services or services that mark the restarted service as Required, the other services also get restarted. For example, running systemctl restart frr.service restarts any of the routing protocol daemons that are enabled and running, such as bgpd or ospfd.
  • reload: Reloads a daemon’s configuration.
  • enable: Enables the daemon to start when the system boots, but does not start it unless you use the systemctl start SERVICENAME.service command or reboot the switch.
  • disable: Disables the daemon, but does not stop it unless you use the systemctl stop SERVICENAME.service command or reboot the switch. A disabled daemon can still be started or stopped.
  • reenable: Disables, then enables a daemon. You might need to do this so that any new Wants or WantedBy lines create the symlinks necessary for ordering. This has no side effects on other daemons.

Ensuring a Service Starts after Multiple Restarts

By default, systemd is configured to try to restart a particular service only a certain number of times within a given interval before the service fails to start at all. The settings for this are stored in the service script. The settings are StartLimitInterval (which defaults to 10 seconds) and StartBurstLimit (which defaults to 5 attempts), but many services override these defaults, sometimes with much longer times. switchd.service, for example, sets StartLimitInterval=10m and StartBurstLimit=3, which means if you restart switchd more than 3 times in 10 minutes, it will not start.

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

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

And 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.

Keeping systemd Services from Hanging after Starting

If you start, restart or reload any systemd service that could be started from another systemd service, you must use the --no-block option with systemctl. Otherwise, that service or even the switch itself may hang after starting or restarting.

Identifying 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:~$ sudo 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 0.0.0.0:53              0.0.0.0:*               LISTEN      444/dnsmasq     
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      874/sshd        
tcp6       0      0 :::53                   :::*                    LISTEN      444/dnsmasq     
tcp6       0      0 :::22                   :::*                    LISTEN      874/sshd        
udp        0      0 0.0.0.0:28450           0.0.0.0:*                           839/dhclient    
udp        0      0 0.0.0.0:53              0.0.0.0:*                           444/dnsmasq     
udp        0      0 0.0.0.0:68              0.0.0.0:*                           839/dhclient    
udp        0      0 192.168.0.42:123        0.0.0.0:*                           907/ntpd        
udp        0      0 127.0.0.1:123           0.0.0.0:*                           907/ntpd        
udp        0      0 0.0.0.0:123             0.0.0.0:*                           907/ntpd        
udp        0      0 0.0.0.0:4784            0.0.0.0:*                           909/ptmd        
udp        0      0 0.0.0.0:3784            0.0.0.0:*                           909/ptmd        
udp        0      0 0.0.0.0:3785            0.0.0.0:*                           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

Identifying Daemons Currently Active or Stopped

To determine which daemons are currently active or stopped, run cl-service-summary:

cumulus@switch:~$ cl-service-summary
Service cron         enabled    active 
Service ssh          enabled    active 
Service syslog       enabled    active     
Service neighmgrd    enabled    active   
Service clagd        enabled    active   
Service lldpd        enabled    active   
Service mstpd        enabled    active   
Service poed                    inactive 
Service portwd                  inactive 
Service ptmd         enabled    active   
Service pwmd         enabled    active   
Service smond        enabled    active   
Service switchd      enabled    active   
Service vxrd         disabled   inactive 
Service vxsnd        disabled   inactive 
Service bgpd         disabled   inactive 
Service isisd        disabled   inactive 
Service ospf6d       disabled   inactive 
Service ospfd        disabled   inactive 
Service rdnbrd       disabled   inactive 
Service ripd         disabled   inactive 
Service ripngd       disabled   inactive 
Service zebra        disabled   inactive 

You can also run systemctl list-unit-files --type service to list all services on the switch and see which ones are enabled:

Click here to see output of this command ...
cumulus@switch:~$ systemctl list-unit-files --type service
UNIT FILE                              STATE   
aclinit.service                        enabled 
acltool.service                        enabled 
acpid.service                          disabled
arp_refresh.service                    enabled 
auditd.service                         enabled 
autovt@.service                        disabled
bootlog.service                        enabled 
bootlogd.service                       masked  
bootlogs.service                       masked  
bootmisc.service                       masked  
checkfs.service                        masked  
checkroot-bootclean.service            masked  
checkroot.service                      masked  
clagd.service                          enabled 
clcmd.service                          enabled 
console-getty.service                  disabled
console-shell.service                  disabled
container-getty@.service               static  
cron.service                           enabled 
cryptdisks-early.service               masked  
cryptdisks.service                     masked  
cumulus-aclcheck.service               static  
cumulus-core.service                   static  
cumulus-fastfailover.service           enabled 
cumulus-firstboot.service              disabled
cumulus-platform.service               enabled 
cumulus-support.service                static  
dbus-org.freedesktop.hostname1.service static  
dbus-org.freedesktop.locale1.service   static  
dbus-org.freedesktop.login1.service    static  
dbus-org.freedesktop.machine1.service  static  
dbus-org.freedesktop.timedate1.service static  
dbus.service                           static  
debian-fixup.service                   static  
debug-shell.service                    disabled
decode-syseeprom.service               static  
dhcpd.service                          disabled
dhcpd6.service                         disabled
dhcpd6@.service                        disabled
dhcpd@.service                         disabled
dhcrelay.service                       enabled 
dhcrelay6.service                      disabled
dhcrelay6@.service                     disabled
dhcrelay@.service                      disabled
dm-event.service                       disabled
dns-watcher.service                    disabled
dnsmasq.service                        enabled 
emergency.service                      static  
fuse.service                           masked  
getty-static.service                   static  
getty@.service                         enabled 
halt-local.service                     static  
halt.service                           masked  
heartbeat-failed@.service              static  
hostname.service                       masked  
hsflowd.service                        enabled 
hsflowd@.service                       enabled 
hwclock-save.service                   enabled 
hwclock.service                        masked  
hwclockfirst.service                   masked  
ifup@.service                          static  
initrd-cleanup.service                 static  
initrd-parse-etc.service               static  
initrd-switch-root.service             static  
initrd-udevadm-cleanup-db.service      static  
killprocs.service                      masked  
kmod-static-nodes.service              static  
kmod.service                           static  
ledmgrd.service                        enabled 
lldpd.service                          enabled 
lm-sensors.service                     enabled 
lvm2-activation-early.service          enabled 
lvm2-activation.service                enabled 
lvm2-lvmetad.service                   static  
lvm2-monitor.service                   enabled 
lvm2-pvscan@.service                   static  
lvm2.service                           disabled
module-init-tools.service              static  
motd.service                           masked  
mountall-bootclean.service             masked  
mountall.service                       masked  
mountdevsubfs.service                  masked  
mountkernfs.service                    masked  
mountnfs-bootclean.service             masked  
mountnfs.service                       masked  
mstpd.service                          enabled 
netd.service                           enabled 
netq-agent.service                     disabled
networking.service                     enabled 
ntp.service                            enabled 
ntp@.service                           disabled
openvswitch-vtep.service               disabled
phy-ucode-update.service               enabled 
portwd.service                         enabled 
procps.service                         static  
ptmd.service                           enabled 
pwmd.service                           enabled 
frr.service                            enabled 
quotaon.service                        static  
rc-local.service                       static  
rc.local.service                       static  
rdnbrd.service                         disabled
reboot.service                         masked  
rescue.service                         static  
rmnologin.service                      masked  
rsyslog.service                        enabled 
screen-cleanup.service                 masked  
sendsigs.service                       masked  
serial-getty@.service                  disabled
single.service                         masked  
smond.service                          enabled 
snmpd.service                          disabled
snmpd@.service                         disabled
snmptrapd.service                      disabled
snmptrapd@.service                     disabled
ssh.service                            enabled 
ssh@.service                           disabled
sshd.service                           enabled 
stop-bootlogd-single.service           masked  
stop-bootlogd.service                  masked  
stopssh.service                        enabled 
sudo.service                           disabled
switchd-diag.service                   static  
switchd.service                        enabled 
syslog.service                         enabled 
sysmonitor.service                     static  
systemd-ask-password-console.service   static  
systemd-ask-password-wall.service      static  
systemd-backlight@.service             static  
systemd-binfmt.service                 static  
systemd-fsck-root.service              static  
systemd-fsck@.service                  static  
systemd-halt.service                   static  
systemd-hibernate.service              static  
systemd-hostnamed.service              static  
systemd-hybrid-sleep.service           static  
systemd-initctl.service                static  
systemd-journal-flush.service          static  
systemd-journald.service               static  
systemd-kexec.service                  static  
systemd-localed.service                static  
systemd-logind.service                 static  
systemd-machined.service               static  
systemd-modules-load.service           static  
systemd-networkd-wait-online.service   disabled
systemd-networkd.service               disabled
systemd-nspawn@.service                disabled
systemd-poweroff.service               static  
systemd-quotacheck.service             static  
systemd-random-seed.service            static  
systemd-readahead-collect.service      disabled
systemd-readahead-done.service         static  
systemd-readahead-drop.service         disabled
systemd-readahead-replay.service       disabled
systemd-reboot.service                 static  
systemd-remount-fs.service             static  
systemd-resolved.service               disabled
systemd-rfkill@.service                static  
systemd-setup-dgram-qlen.service       static  
systemd-shutdownd.service              static  
systemd-suspend.service                static  
systemd-sysctl.service                 static  
systemd-timedated.service              static  
systemd-timesyncd.service              disabled
systemd-tmpfiles-clean.service         static  
systemd-tmpfiles-setup-dev.service     static  
systemd-tmpfiles-setup.service         static  
systemd-udev-settle.service            static  
systemd-udev-trigger.service           static  
systemd-udevd.service                  static  
systemd-update-utmp-runlevel.service   static  
systemd-update-utmp.service            static  
systemd-user-sessions.service          static  
udev-finish.service                    static  
udev.service                           static  
umountfs.service                       masked  
umountnfs.service                      masked  
umountroot.service                     masked  
update-ports.service                   enabled 
urandom.service                        static  
user@.service                          static  
uuidd.service                          static  
vboxadd-service.service                enabled 
vboxadd-x11.service                    enabled 
vboxadd.service                        enabled 
vxrd.service                           disabled
vxsnd.service                          disabled
wd_keepalive.service                   enabled 
x11-common.service                     masked  
ztp-init.service                       enabled 
ztp.service                            disabled
191 unit files listed.
lines 147-194/194 (END)

Identifying Essential Services

If you need to know which services are required to run when the switch boots, run:

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

To see which services are needed for networking, run:

cumulus@switch:~$ sudo systemctl list-dependencies --after network.target
network.target
   ├─networking.service
   ├─switchd.service
   ├─wd_keepalive.service
   └─network-pre.target

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

cumulus@leaf01:~$ sudo systemctl list-dependencies --before multi-user.target
multi-user.target
   ├─bootlog.service
   ├─systemd-readahead-done.service
   ├─systemd-readahead-done.timer
   ├─systemd-update-utmp-runlevel.service
   └─graphical.target
   └─systemd-update-utmp-runlevel.service