[centos7] systemctl 맛보기

<systemctl로 서비스 예제>

먼저 httpd를 설치한다.

$ sudo yum install httpd

(참고로 예시로 사용할 crond는 이미 설치되어 있고 실행중인 데몬이다.)

systemctl 데몬 관련 커맨드

* systemctl start : 데몬 시작

* systemctl stop : 데몬 종료

* systemctl restart : 데몬 재시작

* systemctl reload : 데몬 reload (예, apache graceful )

* systemctl status : 데몬 상태 확인

* systemctl enable : 활성화 - 부팅 이후에도 계속 데몬을 실행할지 

* systemctl disable : 활성화 - 부팅 이후에도 계속 데몬을 실행안하도록

* systemctl is-enabled : 활성화인지 확인한다.

* systemctl is-active : 동작 중인지 확인한다.

예시

$ sudo systemctl start httpd.service

$ sudo systemctl status httpd.service

httpd.service - The Apache HTTP Server

   Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled)

   Active: active (running) since 수 2016-05-11 17:58:17 KST; 4s ago

     Docs: man:httpd(8)

           man:apachectl(8)

 Main PID: 11784 (httpd)

   Status: "Processing requests..."

   CGroup: /system.slice/httpd.service

           ├─11784 /usr/sbin/httpd -DFOREGROUND

           ├─11785 /usr/sbin/httpd -DFOREGROUND

           ├─11786 /usr/sbin/httpd -DFOREGROUND

           ├─11788 /usr/sbin/httpd -DFOREGROUND

           ├─11791 /usr/sbin/httpd -DFOREGROUND

           └─11792 /usr/sbin/httpd -DFOREGROUND

$ sudo systemctl enable httpd.service

ln -s '/usr/lib/systemd/system/httpd.service' '/etc/systemd/system/multi-user.target.wants/httpd.service'

$ sudo systemctl status httpd.service

httpd.service - The Apache HTTP Server

   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)

   Active: active (running) since 수 2016-05-11 17:58:17 KST; 21s ago

     Docs: man:httpd(8)

           man:apachectl(8)

 Main PID: 11784 (httpd)

   Status: "Total requests: 0; Current requests/sec: 0; Current traffic:   0 B/sec"

   CGroup: /system.slice/httpd.service

           ├─11784 /usr/sbin/httpd -DFOREGROUND

           ├─11785 /usr/sbin/httpd -DFOREGROUND

           ├─11786 /usr/sbin/httpd -DFOREGROUND

           ├─11788 /usr/sbin/httpd -DFOREGROUND

           ├─11791 /usr/sbin/httpd -DFOREGROUND

           └─11792 /usr/sbin/httpd -DFOREGROUND

$ sudo systemctl restart httpd.service

$ sudo systemctl status httpd.service

httpd.service - The Apache HTTP Server

   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)

   Active: active (running) since 수 2016-05-11 17:58:53 KST; 2s ago

     Docs: man:httpd(8)

           man:apachectl(8)

  Process: 11831 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)

 Main PID: 11836 (httpd)

   Status: "Processing requests..."

   CGroup: /system.slice/httpd.service

           ├─11836 /usr/sbin/httpd -DFOREGROUND

           ├─11837 /usr/sbin/httpd -DFOREGROUND

           ├─11838 /usr/sbin/httpd -DFOREGROUND

           ├─11839 /usr/sbin/httpd -DFOREGROUND

           ├─11840 /usr/sbin/httpd -DFOREGROUND

           └─11843 /usr/sbin/httpd -DFOREGROUND

$ sudo systemctl reload httpd.service

$ sudo systemctl status httpd.service

httpd.service - The Apache HTTP Server

   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)

   Active: active (running) since 수 2016-05-11 17:58:53 KST; 20s ago

     Docs: man:httpd(8)

           man:apachectl(8)

  Process: 11831 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)

  Process: 11859 ExecReload=/usr/sbin/httpd $OPTIONS -k graceful (code=exited, status=0/SUCCESS)

 Main PID: 11836 (httpd)

   Status: "Total requests: 0; Current requests/sec: 0; Current traffic:   0 B/sec"

   CGroup: /system.slice/httpd.service

           ├─11836 /usr/sbin/httpd -DFOREGROUND

           ├─11860 /usr/sbin/httpd -DFOREGROUND

           ├─11861 /usr/sbin/httpd -DFOREGROUND

           ├─11862 /usr/sbin/httpd -DFOREGROUND

           ├─11863 /usr/sbin/httpd -DFOREGROUND

           └─11864 /usr/sbin/httpd -DFOREGROUND

$ sudo systemctl stop httpd.service

$ sudo systemctl status httpd.service

httpd.service - The Apache HTTP Server

   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)

   Active: inactive (dead) since 수 2016-05-11 17:59:22 KST; 1s ago

     Docs: man:httpd(8)

           man:apachectl(8)

  Process: 11883 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)

  Process: 11859 ExecReload=/usr/sbin/httpd $OPTIONS -k graceful (code=exited, status=0/SUCCESS)

  Process: 11836 ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND (code=exited, status=0/SUCCESS)

 Main PID: 11836 (code=exited, status=0/SUCCESS)

   Status: "Total requests: 0; Current requests/sec: 0; Current traffic:   0 B/sec"

$ sudo systemctl disable httpd.service

rm '/etc/systemd/system/multi-user.target.wants/httpd.service'

$  systemctl is-enabled httpd.service

disabled

$  systemctl is-active httpd.service

unknown

$  systemctl is-active crond.service

inactive

$  systemctl is-enabled crond.service

enabled

서비스 설정 파일 확인하기

$ ls -al /usr/lib/systemd/system/httpd.service

-rw-r--r-- 1 root root 752 11월 20 06:35 /usr/lib/systemd/system/httpd.service

ls -al /usr/lib/systemd/system/crond.service

-rw-r--r--. 1 root root 284  7월 31  2014 /usr/lib/systemd/system/crond.service

<systemctl 커맨드 맛보기>

서비스 타입중 현재 실행중인 시스템 서비스 목록 보기

$ systemctl -t service -a --state running

UNIT                              LOAD   ACTIVE SUB     DESCRIPTION

proc-sys-fs-binfmt_misc.automount loaded active running Arbitrary Executable File Formats File System Automount Point

session-30.scope                  loaded active running Session 30 of user deploy

acpid.service                     loaded active running ACPI Event Daemon

auditd.service                    loaded active running Security Auditing Service

dbus.service                      loaded active running D-Bus System Message Bus

getty@tty1.service                loaded active running Getty on tty1

irqbalance.service                loaded active running irqbalance daemon

network.service                   loaded active running LSB: Bring up/down networking

ntpd.service                      loaded active running Network Time Service

rsyncd.service                    loaded active running fast remote file copy program daemon

rsyslog.service                   loaded active running System Logging Service

snmpd.service                     loaded active running Simple Network Management Protocol (SNMP) Daemon.

sshd.service                      loaded active running OpenSSH server daemon

systemd-journald.service          loaded active running Journal Service

systemd-logind.service            loaded active running Login Service

systemd-udevd.service             loaded active running udev Kernel Device Manager

dbus.socket                       loaded active running D-Bus System Message Bus Socket

systemd-journald.socket           loaded active running Journal Socket

systemd-udevd-control.socket      loaded active running udev Control Socket

systemd-udevd-kernel.socket       loaded active running udev Kernel Socket

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.

20 loaded units listed.

To show all installed unit files use 'systemctl list-unit-files'.

시스템의 모든 서비스의 간단한 모든 상태 정보를 보고 싶다면, 다음을 사용한다. 

$ systemctl --type service --all

UNIT                                  LOAD   ACTIVE   SUB     DESCRIPTION

acpid.service                         loaded active   running ACPI Event Daemon

auditd.service                        loaded active   running Security Auditing Service

brandbot.service                      loaded inactive dead    Flexible Branding Service

cloud-config.service                  loaded active   exited  Apply the settings specified in cloud-config

cloud-final.service                   loaded active   exited  Execute cloud user/final scripts

cloud-init-local.service              loaded active   exited  Initial cloud-init job (pre-networking)

cloud-init.service                    loaded active   exited  Initial cloud-init job (metadata service crawler)

crond.service                         loaded inactive dead    Command Scheduler

dbus.service                          loaded active   running D-Bus System Message Bus

display-manager.service               not-found inactive dead    display-manager.service

dracut-shutdown.service               loaded inactive dead    Restore /run/initramfs

emergency.service                     loaded inactive dead    Emergency Shell

exim.service                          not-found inactive dead    exim.service

getty@tty1.service                    loaded active   running Getty on tty1

ip6tables.service                     not-found inactive dead    ip6tables.service

iptables.service                      not-found inactive dead    iptables.service

유닛 파일 타입의 systemctl로 사용할 수 있는 시스템 서비스 목록을 본다.

$ systemctl list-unit-files

UNIT FILE                              STATE

proc-sys-fs-binfmt_misc.automount      static

dev-hugepages.mount                    static

dev-mqueue.mount                       static

proc-sys-fs-binfmt_misc.mount          static

sys-fs-fuse-connections.mount          static

sys-kernel-config.mount                static

sys-kernel-debug.mount                 static

tmp.mount                              disabled

brandbot.path                          disabled

systemd-ask-password-console.path      static

systemd-ask-password-plymouth.path     static

systemd-ask-password-wall.path         static

session-2.scope                        static

session-29.scope                       static

session-30.scope                       static

session-9.scope                        static

acpid.service                          enabled

arp-ethers.service                     disabled

atd.service                            disabled

auditd.service                         enabled

autovt@.service                        disabled

brandbot.service                       static

cloud-config.service                   enabled

cloud-final.service                    enabled

cloud-init-local.service               enabled

cloud-init.service                     enabled

...

리스닝하는 소켓 타입의 systemctl로 사용할 수 있는 시스템 서비스 목록을 본다.

$ systemctl list-sockets

LISTEN                          UNIT                         ACTIVATES

/dev/initctl                    systemd-initctl.socket       systemd-initctl.service

/dev/log                        systemd-journald.socket      systemd-journald.service

/run/systemd/journal/socket     systemd-journald.socket      systemd-journald.service

/run/systemd/journal/stdout     systemd-journald.socket      systemd-journald.service

/run/systemd/shutdownd          systemd-shutdownd.socket     systemd-shutdownd.service

/run/udev/control               systemd-udevd-control.socket systemd-udevd.service

/var/run/dbus/system_bus_socket dbus.socket                  dbus.service

kobject-uevent 1                systemd-udevd-kernel.socket  systemd-udevd.service

8 sockets listed.

Pass --all to see loaded but inactive sockets, too.

사용할 수 있는 모든 유닛 타입은 다음과 같다.

$ systemctl -t help

Available unit types:

service

socket

target

device

mount

automount

snapshot

timer

swap

path

slice

scope

특정 서비스의 dependency 유닛을 보려면 다음과 같은 커맨드를 사용한다.

$ systemctl list-dependencies crond.service

crond.service

├─system.slice

└─basic.target

  ├─microcode.service

  ├─rhel-autorelabel-mark.service

  ├─rhel-autorelabel.service

  ├─rhel-configure.service

  ├─rhel-dmesg.service

  ├─rhel-loadmodules.service

  ├─paths.target

  ├─slices.target

  │ ├─-.slice

  │ └─system.slice

  ├─sockets.target

  │ ├─dbus.socket

  │ ├─rsyncd.socket

  │ ├─systemd-initctl.socket

  │ ├─systemd-journald.socket

  │ ├─systemd-shutdownd.socket

  │ ├─systemd-udevd-control.socket

  │ └─systemd-udevd-kernel.socket

  ├─sysinit.target

  │ ├─dev-hugepages.mount

  │ ├─dev-mqueue.mount

  │ ├─kmod-static-nodes.service

  │ ├─plymouth-read-write.service

  │ ├─plymouth-start.service

  │ ├─proc-sys-fs-binfmt_misc.automount

  │ ├─sys-fs-fuse-connections.mount

  │ ├─sys-kernel-config.mount

  │ ├─sys-kernel-debug.mount

  │ ├─systemd-ask-password-console.path

  │ ├─systemd-binfmt.service

  │ ├─systemd-journal-flush.service

  │ ├─systemd-journald.service

  │ ├─systemd-modules-load.service

  │ ├─systemd-random-seed.service

  │ ├─systemd-sysctl.service

  │ ├─systemd-tmpfiles-setup-dev.service

  │ ├─systemd-tmpfiles-setup.service

  │ ├─systemd-udev-trigger.service

  │ ├─systemd-udevd.service

  │ ├─systemd-update-utmp.service

  │ ├─systemd-vconsole-setup.service

  │ ├─cryptsetup.target

  │ ├─local-fs.target

  │ │ ├─-.mount

  │ │ ├─rhel-import-state.service

  │ │ ├─rhel-readonly.service

  │ │ ├─systemd-fsck-root.service

  │ │ └─systemd-remount-fs.service

  │ └─swap.target

  │   └─swap-swapfile1.swap

  └─timers.target

    └─systemd-tmpfiles-clean.timer