systemdのメモ(サービス編)

CentOS7の systemd についてメモ。今回は systemd を用いてサービスの状態について表示したり、操作したり行いましょう。

システムコマンドで起動確認。

  • systemctl -t service
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[root@localhost vagrant]# systemctl -t service
UNIT                               LOAD   ACTIVE SUB     DESCRIPTION
auditd.service                     loaded active running Security Auditing Service
crond.service                      loaded active running Command Scheduler
dbus.service                       loaded active running D-Bus System Message Bus
firewalld.service                  loaded active running firewalld - dynamic firewall daemon
getty@tty1.service                 loaded active running Getty on tty1
kmod-static-nodes.service          loaded active exited  Create list of required static device nodes for the current kernel
lvm2-lvmetad.service               loaded active running LVM2 metadata daemon
lvm2-monitor.service               loaded active exited  Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progress polling
lvm2-pvscan@8:2.service            loaded active exited  LVM2 PV scan on device 8:2
network.service                    loaded failed failed  LSB: Bring up/down networking
(省略)
systemd-udev-trigger.service       loaded active exited  udev Coldplug all Devices
systemd-udevd.service              loaded active running udev Kernel Device Manager
systemd-update-utmp.service        loaded active exited  Update UTMP about System Reboot/Shutdown
systemd-user-sessions.service      loaded active exited  Permit User Sessions
systemd-vconsole-setup.service     loaded active exited  Setup Virtual Console
tuned.service                      loaded active running Dynamic System Tuning Daemon
vboxadd-service.service            loaded active running LSB: VirtualBox Additions service
vboxadd-x11.service                loaded active exited  LSB: VirtualBox Linux Additions kernel modules
vboxadd.service                    loaded active exited  LSB: VirtualBox Linux Additions kernel modules

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

32 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.

起動していないサービスも表示

  • systemctl -t service -all
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[root@localhost vagrant]# systemctl -t service -all
UNIT                                 LOAD   ACTIVE   SUB     DESCRIPTION
auditd.service                       loaded active   running Security Auditing Service
brandbot.service                     loaded inactive dead    Flexible Branding Service
cpupower.service                     loaded inactive dead    Configure CPU power related settings
crond.service                        loaded active   running Command Scheduler
dbus.service                         loaded active   running D-Bus System Message Bus
display-manager.service              not-found inactive dead    display-manager.service
dm-event.service                     loaded inactive dead    Device-mapper event daemon
dracut-shutdown.service              loaded inactive dead    Restore /run/initramfs
ebtables.service                     loaded inactive dead    Ethernet Bridge Filtering tables
emergency.service                    loaded inactive dead    Emergency Shell
exim.service                         not-found inactive dead    exim.service
firewalld.service                    loaded active   running firewalld - dynamic firewall daemon
(省略)
sshd.service                         loaded active   running OpenSSH server daemon
syslog.service                       not-found inactive dead    syslog.service
systemd-ask-password-console.service loaded inactive dead    Dispatch Password Requests to Console
systemd-ask-password-wall.service    loaded inactive dead    Forward Password Requests to Wall
systemd-binfmt.service               loaded inactive dead    Set Up Additional Binary Formats
systemd-fsck-root.service            loaded inactive dead    File System Check on Root Device
systemd-initctl.service              loaded inactive dead    /dev/initctl Compatibility Daemon
systemd-journal-flush.service        loaded inactive dead    Trigger Flushing of Journal to Persistent Storage

定義されているUNITの設定を確認することができる。

  • systemctl list-unit-files --type=service
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[root@localhost vagrant]# systemctl list-unit-files --type=service
UNIT FILE                                   STATE
auditd.service                              enabled
auth-rpcgss-module.service                  static
autovt@.service                             disabled
blk-availability.service                    disabled
brandbot.service                            static
console-getty.service                       disabled
console-shell.service                       disabled
cpupower.service                            disabled
crond.service                               enabled
  • enable - 有効
  • disabled - 無効
  • static - 自動起動設定を持たない

UNITを有効化・無効化する。

  • 無効化 systemctl disable UNIT-name

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    [root@localhost vagrant]# systemctl list-unit-files --type=service | grep send
    sendmail.service                            enabled
    [root@localhost vagrant]# systemctl disable sendmail
    rm '/etc/systemd/system/multi-user.target.wants/sendmail.service'
    rm '/etc/systemd/system/multi-user.target.wants/sm-client.service'
    [root@localhost vagrant]# systemctl list-unit-files --type=service | grep sendmail
    sendmail.service                            disabled

  • 有効化 systemctl enable UNIT-name

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    ot@localhost vagrant]# systemctl list-unit-files --type=service | grep sendmail
    sendmail.service                            disabled
    [root@localhost vagrant]# systemctl enable sendmail
    ln -s '/usr/lib/systemd/system/sendmail.service' '/etc/systemd/system/multi-user.target.wants/sendmail.service'
    ln -s '/usr/lib/systemd/system/sm-client.service' '/etc/systemd/system/multi-user.target.wants/sm-client.service'
    [root@localhost vagrant]# systemctl list-unit-files --type=service | grep sendmail
    sendmail.service                            enabled

サービスの操作(起動・停止など)

  • サービス起動 systemctl start Unit-name

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    [root@localhost vagrant]# ps auxfw | grep -i [s]endmai
    [root@localhost vagrant]# systemctl start sendmail
    [root@localhost vagrant]# ps auxfw | grep -i [s]endmai
    root      1333  0.0  0.4  90208  2264 ?        Ss   12:57   0:00 sendmail: accepting connections
    smmsp     1345  0.0  0.4  85648  1900 ?        Ss   12:57   0:00 sendmail: Queue runner@01:00:00 for /var/spool/clientmqueue

  • サービス停止 systemctl stop Unit-name

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    [root@localhost vagrant]# ps auxfw | grep -i [s]endmai
    root      1333  0.0  0.4  90208  2264 ?        Ss   12:57   0:00 sendmail: accepting connections
    smmsp     1345  0.0  0.4  85648  1900 ?        Ss   12:57   0:00 sendmail: Queue runner@01:00:00 for /var/spool/clientmqueue
    [root@localhost vagrant]# systemctl stop sendmail
    [root@localhost vagrant]# ps auxfw | grep -i [s]endmai
    [root@localhost vagrant]#

  • サービス再起動 systemctl restart Unit-name

  • サービス再読込 systemctl reload Unit-name

    • reload 設定がない場合はエラーになる。

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      [root@localhost vagrant]# systemctl reload sendmail
      Failed to issue method call: Job type reload is not applicable for unit sendmail.service.

追記(2015/05/20)

UNITってなんですか？と@harasou さんにご質問を頂いたので回答。

UNITとは？

systemdが操作することができるサービス名のこと。
タイプとして、target, mount, service, device の４種類分かれている。

運用で主に、使うことになるのはserviceであろう。