systemctl 命令不完全指南
Systemctl是一个systemd工具，主要负责控制systemd系统和服务管理器。
Systemd是一个系统管理守护进程、工具和库的集合，用于取代System V初始进程。Systemd的功能是用于集中管理和配置类UNIX系统。
在Linux生态系统中，Systemd被部署到了大多数的标准Linux发行版中，只有为数不多的几个发行版尚未部署。Systemd通常是所有其它守护进程的父进程，但并非总是如此。
本文旨在阐明在运行systemd的系统上“如何控制系统和服务”。
Systemd初体验和Systemctl基础
1. 首先检查你的系统中是否安装有systemd并确定当前安装的版本
<![if !supportLists]>1. <![endif]># systemctl –version
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>systemd 215
<![if !supportLists]>4. <![endif]>+PAM +AUDIT +SELINUX +IMA +SYSVINIT
+LIBCRYPTSETUP +GCRYPT +ACL +XZ -SECCOMP -APPARMOR
上例中很清楚地表明，我们安装了215版本的systemd。
2. 检查systemd和systemctl的二进制文件和库文件的安装位置
<![if !supportLists]>1. <![endif]># whereis systemd
<![if !supportLists]>2. <![endif]>systemd: /usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gz
<![if !supportLists]>3. <![endif]>
<![if !supportLists]>4. <![endif]>
<![if !supportLists]>5. <![endif]># whereis systemctl
<![if !supportLists]>6. <![endif]>systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz
3. 检查systemd是否运行
<![if !supportLists]>1. <![endif]># ps -eaf | grep [s]ystemd
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>root
1 0 0 16:27 ? 00:00:00 /usr/lib/systemd/systemd –switched-root –system –deserialize 23
<![if !supportLists]>4. <![endif]>root 444
1
0 16:27 ? 00:00:00 /usr/lib/systemd/systemd-journald
<![if !supportLists]>5. <![endif]>root 469
1
0 16:27 ? 00:00:00 /usr/lib/systemd/systemd-udevd
<![if !supportLists]>6. <![endif]>root 555
1
0 16:27 ? 00:00:00 /usr/lib/systemd/systemd-logind
<![if !supportLists]>7. <![endif]>dbus 556
1
0 16:27 ? 00:00:00 /bin/dbus-daemon –system –address=systemd: –nofork –nopidfile –systemd-activation
注意：systemd是作为父进程（PID=1）运行的。在上面带（-e）参数的ps命令输出中，选择所有进程，（-a）选择除会话前导外的所有进程，并使用（-f）参数输出完整格式列表（即 -eaf）。
也请注意上例中后随的方括号和例子中剩余部分。方括号表达式是grep的字符类表达式的一部分。
4. 分析systemd启动进程
<![if !supportLists]>1. <![endif]># systemd-analyze
<![if !supportLists]>2. <![endif]>Startup finished in 487ms (kernel) + 2.776s (initrd) + 20.229s (userspace) = 23.493s
5. 分析启动时各个进程花费的时间
<![if !supportLists]>1. <![endif]># systemd-analyze blame
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>8.565s mariadb.service
<![if !supportLists]>4. <![endif]>7.991s webmin.service
<![if !supportLists]>5. <![endif]>6.095s postfix.service
<![if !supportLists]>6. <![endif]>4.311s httpd.service
<![if !supportLists]>7. <![endif]>3.926s firewalld.service
<![if !supportLists]>8. <![endif]>3.780s kdump.service
<![if !supportLists]>9. <![endif]>3.238s tuned.service
<![if !supportLists]>10. <![endif]>1.712s network.service
<![if !supportLists]>11. <![endif]>1.394s lvm2-monitor.service
<![if !supportLists]>12. <![endif]>1.126s systemd-logind.service
<![if !supportLists]>13. <![endif]>….
6. 分析启动时的关键链
<![if !supportLists]>1. <![endif]># systemd-analyze critical-chain
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>The time after the unit is
active or started is
printed after the "@" character.
<![if !supportLists]>4. <![endif]>The time the unit takes to start is printed after the "+" character.
<![if !supportLists]>5. <![endif]>
<![if !supportLists]>6. <![endif]>multi-user.target
@20.222s
<![if !supportLists]>7. <![endif]>└─mariadb.service
@11.657s +8.565s
<![if !supportLists]>8. <![endif]> └─network.target
@11.168s
<![if !supportLists]>9. <![endif]> └─network.service
@9.456s +1.712s
<![if !supportLists]>10. <![endif]> └─NetworkManager.service @8.858s +596ms
<![if !supportLists]>11. <![endif]> └─firewalld.service @4.931s +3.926s
<![if !supportLists]>12. <![endif]> └─basic.target @4.916s
<![if !supportLists]>13. <![endif]> └─sockets.target @4.916s
<![if !supportLists]>14. <![endif]> └─dbus.socket @4.916s
<![if !supportLists]>15. <![endif]> └─sysinit.target @4.905s
<![if !supportLists]>16. <![endif]> └─systemd-update-utmp.service
@4.864s +39ms
<![if !supportLists]>17. <![endif]> └─auditd.service @4.563s +301ms
<![if !supportLists]>18. <![endif]> └─systemd-tmpfiles-setup.service @4.485s +69ms
<![if !supportLists]>19. <![endif]> └─rhel-import-state.service @4.342s +142ms
<![if !supportLists]>20. <![endif]> └─local-fs.target @4.324s
<![if !supportLists]>21. <![endif]> └─boot.mount @4.286s +31ms
<![if !supportLists]>22. <![endif]> └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d19608096
<![if !supportLists]>23. <![endif]> └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4
重要：Systemctl接受服务（.service），挂载点（.mount），套接口（.socket）和设备（.device）作为单元。
7. 列出所有可用单元
<![if !supportLists]>1. <![endif]># systemctl list-unit-files
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>UNIT FILE
STATE
<![if !supportLists]>4. <![endif]>proc-sys-fs-binfmt_misc.automount
static
<![if !supportLists]>5. <![endif]>dev-hugepages.mount
static
<![if !supportLists]>6. <![endif]>dev-mqueue.mount
static
<![if !supportLists]>7. <![endif]>proc-sys-fs-binfmt_misc.mount
static
<![if !supportLists]>8. <![endif]>sys-fs-fuse-connections.mount
static
<![if !supportLists]>9. <![endif]>sys-kernel-config.mount
static
<![if !supportLists]>10. <![endif]>sys-kernel-debug.mount
static
<![if !supportLists]>11. <![endif]>tmp.mount
disabled
<![if !supportLists]>12. <![endif]>brandbot.path
disabled
<![if !supportLists]>13. <![endif]>…..
8. 列出所有运行中单元
<![if !supportLists]>1. <![endif]># systemctl list-units
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>UNIT
LOAD ACTIVE SUB
DESCRIPTION
<![if !supportLists]>4. <![endif]>proc-sys-fs-binfmt_misc.automount
loaded active waiting Arbitrary Executable File Formats File Syste
<![if !supportLists]>5. <![endif]>sys-devices-pc…0-1:0:0:0-block-sr0.device loaded active plugged VBOX_CD-ROM
<![if !supportLists]>6. <![endif]>sys-devices-pc…:00:03.0-net-enp0s3.device loaded active plugged PRO/1000 MT Desktop Adapter
<![if !supportLists]>7. <![endif]>sys-devices-pc…00:05.0-sound-card0.device loaded active plugged 82801AA AC‘97 Audio Controller
<![if !supportLists]>8. <![endif]>sys-devices-pc…:0:0-block-sda-sda1.device
loaded active plugged
VBOX_HARDDISK
<![if !supportLists]>9. <![endif]>sys-devices-pc…:0:0-block-sda-sda2.device
loaded active plugged LVM PV
Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8
<![if !supportLists]>10. <![endif]>sys-devices-pc…0-2:0:0:0-block-sda.device
loaded active plugged
VBOX_HARDDISK
<![if !supportLists]>11. <![endif]>sys-devices-pl…erial8250-tty-ttyS0.device loaded active
plugged
/sys/devices/platform/serial8250/tty/ttyS0
<![if !supportLists]>12. <![endif]>sys-devices-pl…erial8250-tty-ttyS1.device loaded active
plugged
/sys/devices/platform/serial8250/tty/ttyS1
<![if !supportLists]>13. <![endif]>sys-devices-pl…erial8250-tty-ttyS2.device loaded active
plugged
/sys/devices/platform/serial8250/tty/ttyS2
<![if !supportLists]>14. <![endif]>sys-devices-pl…erial8250-tty-ttyS3.device loaded active
plugged /sys/devices/platform/serial8250/tty/ttyS3
<![if !supportLists]>15. <![endif]>sys-devices-virtual-block-dm\x2d0.device loaded active plugged /sys/devices/virtual/block/dm-0
<![if !supportLists]>16. <![endif]>sys-devices-virtual-block-dm\x2d1.device loaded active plugged /sys/devices/virtual/block/dm-1
<![if !supportLists]>17. <![endif]>sys-module-configfs.device
loaded active plugged
/sys/module/configfs
<![if !supportLists]>18. <![endif]>…
9. 列出所有失败单元
<![if !supportLists]>1. <![endif]># systemctl –failed
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>UNIT
LOAD ACTIVE SUB DESCRIPTION
<![if !supportLists]>4. <![endif]>kdump.service loaded failed failed
Crash recovery kernel arming
<![if !supportLists]>5. <![endif]>
<![if !supportLists]>6. <![endif]>LOAD = Reflects
whether the unit definition was properly loaded.
<![if !supportLists]>7. <![endif]>ACTIVE = The high-level unit activation state, i.e. generalization of
SUB.
<![if !supportLists]>8. <![endif]>SUB = The low-level unit activation state, values depend on unit
type.
<![if !supportLists]>9. <![endif]>
<![if !supportLists]>10. <![endif]>1 loaded units listed. Pass
–all to see loaded but inactive units, too.
<![if !supportLists]>11. <![endif]>To show all installed unit files use ‘systemctl
list-unit-files’.
10. 检查某个单元（如 cron.service）是否启用
<![if !supportLists]>1. <![endif]># systemctl is-enabled crond.service
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>enabled
11. 检查某个单元或服务是否运行
<![if !supportLists]>1. <![endif]># systemctl status firewalld.service
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>firewalld.service - firewalld -
dynamic firewall daemon
<![if !supportLists]>4. <![endif]> Loaded:
loaded (/usr/lib/systemd/system/firewalld.service;
enabled)
<![if !supportLists]>5. <![endif]> Active:
active (running) since Tue 2015-04-28 16:27:55 IST; 34min ago
<![if !supportLists]>6. <![endif]> Main PID: 549 (firewalld)
<![if !supportLists]>7. <![endif]> CGroup: /system.slice/firewalld.service
<![if !supportLists]>8. <![endif]> └─549 /usr/bin/python -Es /usr/sbin/firewalld –nofork –nopid
<![if !supportLists]>9. <![endif]>
<![if !supportLists]>10. <![endif]>Apr 28 16:27:51 tecmint systemd[1]: Starting firewalld - dynamic firewall
daemon…
<![if !supportLists]>11. <![endif]>Apr 28 16:27:55 tecmint systemd[1]: Started firewalld - dynamic firewall
daemon.
使用Systemctl控制并管理服务
12. 列出所有服务（包括启用的和禁用的）
<![if !supportLists]>1. <![endif]># systemctl list-unit-files –type=service
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>UNIT FILE
STATE
<![if !supportLists]>4. <![endif]>arp-ethers.service
disabled
<![if !supportLists]>5. <![endif]>auditd.service
enabled
<![if !supportLists]>6. <![endif]>autovt@.service
disabled
<![if !supportLists]>7. <![endif]>blk-availability.service
disabled
<![if !supportLists]>8. <![endif]>brandbot.service
static
<![if !supportLists]>9. <![endif]>collectd.service
disabled
<![if !supportLists]>10. <![endif]>console-getty.service
disabled
<![if !supportLists]>11. <![endif]>console-shell.service
disabled
<![if !supportLists]>12. <![endif]>cpupower.service
disabled
<![if !supportLists]>13. <![endif]>crond.service
enabled
<![if !supportLists]>14. <![endif]>dbus-org.fedoraproject.FirewallD1.service
enabled
<![if !supportLists]>15. <![endif]>….
13. Linux中如何启动、重启、停止、重载服务以及检查服务（如 httpd.service）状态
<![if !supportLists]>1. <![endif]># systemctl start httpd.service
<![if !supportLists]>2. <![endif]># systemctl restart httpd.service
<![if !supportLists]>3. <![endif]># systemctl stop httpd.service
<![if !supportLists]>4. <![endif]># systemctl reload httpd.service
<![if !supportLists]>5. <![endif]># systemctl status httpd.service
<![if !supportLists]>6. <![endif]>
<![if !supportLists]>7. <![endif]>httpd.service - The Apache HTTP Server
<![if !supportLists]>8. <![endif]> Loaded:
loaded (/usr/lib/systemd/system/httpd.service;
enabled)
<![if !supportLists]>9. <![endif]> Active:
active (running) since Tue 2015-04-28 17:21:30 IST; 6s ago
<![if !supportLists]>10. <![endif]> Process: 2876 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)
<![if !supportLists]>11. <![endif]> Main PID: 2881 (httpd)
<![if !supportLists]>12. <![endif]> Status: "Processing requests…"
<![if !supportLists]>13. <![endif]> CGroup: /system.slice/httpd.service
<![if !supportLists]>14. <![endif]> ├─2881 /usr/sbin/httpd -DFOREGROUND
<![if !supportLists]>15. <![endif]> ├─2884 /usr/sbin/httpd -DFOREGROUND
<![if !supportLists]>16. <![endif]> ├─2885 /usr/sbin/httpd -DFOREGROUND
<![if !supportLists]>17. <![endif]> ├─2886 /usr/sbin/httpd -DFOREGROUND
<![if !supportLists]>18. <![endif]> ├─2887 /usr/sbin/httpd -DFOREGROUND
<![if !supportLists]>19. <![endif]> └─2888 /usr/sbin/httpd -DFOREGROUND
<![if !supportLists]>20. <![endif]>
<![if !supportLists]>21. <![endif]>Apr 28 17:21:30 tecmint systemd[1]: Starting The Apache HTTP Server…
<![if !supportLists]>22. <![endif]>Apr 28 17:21:30 tecmint httpd[2881]: AH00558: httpd:
Could not reliably determine the server‘s fully q…ssage
<![if !supportLists]>23. <![endif]>Apr 28 17:21:30 tecmint
systemd[1]:
Started The Apache HTTP Server.
<![if !supportLists]>24. <![endif]>Hint: Some lines were ellipsized,
use -l to show in full.
注意：当我们使用systemctl的start，restart，stop和reload命令时，我们不会从终端获取到任何输出内容，只有status命令可以打印输出。
14. 如何激活服务并在启动时启用或禁用服务（即系统启动时自动启动服务）
<![if !supportLists]>1. <![endif]># systemctl is-active httpd.service
<![if !supportLists]>2. <![endif]># systemctl enable httpd.service
<![if !supportLists]>3. <![endif]># systemctl disable httpd.service
15. 如何屏蔽（让它不能启动）或显示服务（如 httpd.service）
<![if !supportLists]>1. <![endif]># systemctl mask httpd.service
<![if !supportLists]>2. <![endif]>ln -s ‘/dev/null’ ‘/etc/systemd/system/httpd.service‘
<![if !supportLists]>3. <![endif]>
<![if !supportLists]>4. <![endif]># systemctl unmask httpd.service
<![if !supportLists]>5. <![endif]>rm ‘/etc/systemd/system/httpd.service‘
16. 使用systemctl命令杀死服务
<![if !supportLists]>1. <![endif]># systemctl kill httpd
<![if !supportLists]>2. <![endif]># systemctl status httpd
<![if !supportLists]>3. <![endif]>
<![if !supportLists]>4. <![endif]>httpd.service - The Apache HTTP Server
<![if !supportLists]>5. <![endif]> Loaded:
loaded (/usr/lib/systemd/system/httpd.service;
enabled)
<![if !supportLists]>6. <![endif]> Active:
failed (Result: exit-code) since Tue 2015-04-28 18:01:42 IST; 28min ago
<![if !supportLists]>7. <![endif]> Main PID: 2881 (code=exited, status=0/SUCCESS)
<![if !supportLists]>8. <![endif]> Status: "Total requests: 0; Current
requests/sec: 0; Current traffic:
0 B/sec"
<![if !supportLists]>9. <![endif]>
<![if !supportLists]>10. <![endif]>Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>11. <![endif]>Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>12. <![endif]>Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>13. <![endif]>Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>14. <![endif]>Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>15. <![endif]>Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>16. <![endif]>Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>17. <![endif]>Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification
message from PID 2881,
but recepti…bled.
<![if !supportLists]>18. <![endif]>Apr 28 18:01:42 tecmint systemd[1]: httpd.service: control process exited, code=exited status=226
<![if !supportLists]>19. <![endif]>Apr 28 18:01:42 tecmint systemd[1]: Unit httpd.service entered failed
state.
<![if !supportLists]>20. <![endif]>Hint: Some lines were ellipsized,
use -l to show in full.
使用Systemctl控制并管理挂载点
17. 列出所有系统挂载点
<![if !supportLists]>1. <![endif]># systemctl list-unit-files –type=mount
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>UNIT FILE
STATE
<![if !supportLists]>4. <![endif]>dev-hugepages.mount
static
<![if !supportLists]>5. <![endif]>dev-mqueue.mount
static
<![if !supportLists]>6. <![endif]>proc-sys-fs-binfmt_misc.mount static
<![if !supportLists]>7. <![endif]>sys-fs-fuse-connections.mount static
<![if !supportLists]>8. <![endif]>sys-kernel-config.mount static
<![if !supportLists]>9. <![endif]>sys-kernel-debug.mount static
<![if !supportLists]>10. <![endif]>tmp.mount
disabled
18. 挂载、卸载、重新挂载、重载系统挂载点并检查系统中挂载点状态
<![if !supportLists]>1. <![endif]># systemctl start tmp.mount
<![if !supportLists]>2. <![endif]># systemctl stop tmp.mount
<![if !supportLists]>3. <![endif]># systemctl restart tmp.mount
<![if !supportLists]>4. <![endif]># systemctl reload tmp.mount
<![if !supportLists]>5. <![endif]># systemctl status tmp.mount
<![if !supportLists]>6. <![endif]>
<![if !supportLists]>7. <![endif]>tmp.mount - Temporary Directory
<![if !supportLists]>8. <![endif]> Loaded:
loaded (/usr/lib/systemd/system/tmp.mount; disabled)
<![if !supportLists]>9. <![endif]> Active:
active (mounted) since Tue 2015-04-28 17:46:06 IST; 2min 48s ago
<![if !supportLists]>10. <![endif]> Where: /tmp
<![if !supportLists]>11. <![endif]> What: tmpfs
<![if !supportLists]>12. <![endif]> Docs: man:hier(7)
<![if !supportLists]>13. <![endif]>
<![if !supportLists]>14. <![endif]>http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
<![if !supportLists]>15. <![endif]>
<![if !supportLists]>16. <![endif]> Process: 3908 ExecMount=/bin/mount tmpfs /tmp
-t tmpfs -o mode=1777,strictatime
(code=exited, status=0/SUCCESS)
<![if !supportLists]>17. <![endif]>
<![if !supportLists]>18. <![endif]>Apr 28 17:46:06 tecmint systemd[1]: Mounting Temporary Directory…
<![if !supportLists]>19. <![endif]>Apr 28 17:46:06 tecmint systemd[1]: tmp.mount: Directory /tmp to mount over is not empty, mounting anyway.
<![if !supportLists]>20. <![endif]>Apr 28 17:46:06 tecmint systemd[1]: Mounted Temporary Directory.
19. 在启动时激活、启用或禁用挂载点（系统启动时自动挂载）
<![if !supportLists]>1. <![endif]># systemctl is-active tmp.mount
<![if !supportLists]>2. <![endif]># systemctl enable tmp.mount
<![if !supportLists]>3. <![endif]># systemctl disable tmp.mount
20. 在Linux中屏蔽（让它不能启用）或可见挂载点
<![if !supportLists]>1. <![endif]># systemctl mask tmp.mount
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>ln -s ‘/dev/null’ ‘/etc/systemd/system/tmp.mount‘
<![if !supportLists]>4. <![endif]>
<![if !supportLists]>5. <![endif]># systemctl unmask tmp.mount
<![if !supportLists]>6. <![endif]>
<![if !supportLists]>7. <![endif]>rm ‘/etc/systemd/system/tmp.mount‘
使用Systemctl控制并管理套接口
21. 列出所有可用系统套接口
<![if !supportLists]>1. <![endif]># systemctl list-unit-files –type=socket
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>UNIT FILE
STATE
<![if !supportLists]>4. <![endif]>dbus.socket
static
<![if !supportLists]>5. <![endif]>dm-event.socket
enabled
<![if !supportLists]>6. <![endif]>lvm2-lvmetad.socket
enabled
<![if !supportLists]>7. <![endif]>rsyncd.socket
disabled
<![if !supportLists]>8. <![endif]>sshd.socket
disabled
<![if !supportLists]>9. <![endif]>syslog.socket
static
<![if !supportLists]>10. <![endif]>systemd-initctl.socket static
<![if !supportLists]>11. <![endif]>systemd-journald.socket static
<![if !supportLists]>12. <![endif]>systemd-shutdownd.socket static
<![if !supportLists]>13. <![endif]>systemd-udevd-control.socket static
<![if !supportLists]>14. <![endif]>systemd-udevd-kernel.socket
static
<![if !supportLists]>15. <![endif]>
<![if !supportLists]>16. <![endif]>11 unit files listed.
22. 在Linux中启动、重启、停止、重载套接口并检查其状态
<![if !supportLists]>1. <![endif]># systemctl start cups.socket
<![if !supportLists]>2. <![endif]># systemctl restart cups.socket
<![if !supportLists]>3. <![endif]># systemctl stop cups.socket
<![if !supportLists]>4. <![endif]># systemctl reload cups.socket
<![if !supportLists]>5. <![endif]># systemctl status cups.socket
<![if !supportLists]>6. <![endif]>
<![if !supportLists]>7. <![endif]>cups.socket - CUPS Printing Service Sockets
<![if !supportLists]>8. <![endif]> Loaded:
loaded (/usr/lib/systemd/system/cups.socket;
enabled)
<![if !supportLists]>9. <![endif]> Active:
active (listening) since Tue 2015-04-28 18:10:59 IST; 8s ago
<![if !supportLists]>10. <![endif]> Listen: /var/run/cups/cups.sock
(Stream)
<![if !supportLists]>11. <![endif]>
<![if !supportLists]>12. <![endif]>Apr 28 18:10:59 tecmint systemd[1]: Starting CUPS Printing Service Sockets.
<![if !supportLists]>13. <![endif]>Apr 28 18:10:59 tecmint systemd[1]: Listening on CUPS Printing Service Sockets.
23. 在启动时激活套接口，并启用或禁用它（系统启动时自启动）
<![if !supportLists]>1. <![endif]># systemctl is-active cups.socket
<![if !supportLists]>2. <![endif]># systemctl enable cups.socket
<![if !supportLists]>3. <![endif]># systemctl disable cups.socket
24. 屏蔽（使它不能启动）或显示套接口
<![if !supportLists]>1. <![endif]># systemctl mask cups.socket
<![if !supportLists]>2. <![endif]>ln -s ‘/dev/null’ ‘/etc/systemd/system/cups.socket‘
<![if !supportLists]>3. <![endif]>
<![if !supportLists]>4. <![endif]># systemctl unmask cups.socket
<![if !supportLists]>5. <![endif]>rm ‘/etc/systemd/system/cups.socket‘
服务的CPU利用率（分配额）
25. 获取当前某个服务的CPU分配额（如httpd）
<![if !supportLists]>1. <![endif]># systemctl show -p CPUShares httpd.service
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>CPUShares=1024
注意：各个服务的默认CPU分配份额=1024，你可以增加/减少某个进程的CPU分配份额。
26. 将某个服务（httpd.service）的CPU分配份额限制为2000 CPUShares/
<![if !supportLists]>1. <![endif]># systemctl set-property httpd.service CPUShares=2000
<![if !supportLists]>2. <![endif]># systemctl show -p CPUShares httpd.service
<![if !supportLists]>3. <![endif]>
<![if !supportLists]>4. <![endif]>CPUShares=2000
注意：当你为某个服务设置CPUShares，会自动创建一个以服务名命名的目录（如 httpd.service），里面包含了一个名为90-CPUShares.conf的文件，该文件含有CPUShare限制信息，你可以通过以下方式查看该文件：
<![if !supportLists]>1. <![endif]># vi /etc/systemd/system/httpd.service.d/90-CPUShares.conf
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>[Service]
<![if !supportLists]>4. <![endif]>CPUShares=2000
27. 检查某个服务的所有配置细节
<![if !supportLists]>1. <![endif]># systemctl show httpd
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>Id=httpd.service
<![if !supportLists]>4. <![endif]>Names=httpd.service
<![if !supportLists]>5. <![endif]>Requires=basic.target
<![if !supportLists]>6. <![endif]>Wants=system.slice
<![if !supportLists]>7. <![endif]>WantedBy=multi-user.target
<![if !supportLists]>8. <![endif]>Conflicts=shutdown.target
<![if !supportLists]>9. <![endif]>Before=shutdown.target multi-user.target
<![if !supportLists]>10. <![endif]>After=network.target remote-fs.target nss-lookup.target systemd-journald.socket basic.target system.slice
<![if !supportLists]>11. <![endif]>Description=The Apache HTTP Server
<![if !supportLists]>12. <![endif]>LoadState=loaded
<![if !supportLists]>13. <![endif]>ActiveState=active
<![if !supportLists]>14. <![endif]>SubState=running
<![if !supportLists]>15. <![endif]>FragmentPath=/usr/lib/systemd/system/httpd.service
<![if !supportLists]>16. <![endif]>….
28. 分析某个服务（httpd）的关键链
<![if !supportLists]>1. <![endif]># systemd-analyze critical-chain httpd.service
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>The time after the unit is
active or started is
printed after the "@" character.
<![if !supportLists]>4. <![endif]>The time the unit takes to start is printed after the "+" character.
<![if !supportLists]>5. <![endif]>
<![if !supportLists]>6. <![endif]>httpd.service +142ms
<![if !supportLists]>7. <![endif]>└─network.target
@11.168s
<![if !supportLists]>8. <![endif]> └─network.service
@9.456s +1.712s
<![if !supportLists]>9. <![endif]> └─NetworkManager.service @8.858s +596ms
<![if !supportLists]>10. <![endif]> └─firewalld.service @4.931s +3.926s
<![if !supportLists]>11. <![endif]> └─basic.target @4.916s
<![if !supportLists]>12. <![endif]> └─sockets.target @4.916s
<![if !supportLists]>13. <![endif]> └─dbus.socket @4.916s
<![if !supportLists]>14. <![endif]> └─sysinit.target @4.905s
<![if !supportLists]>15. <![endif]> └─systemd-update-utmp.service
@4.864s +39ms
<![if !supportLists]>16. <![endif]> └─auditd.service @4.563s +301ms
<![if !supportLists]>17. <![endif]> └─systemd-tmpfiles-setup.service @4.485s +69ms
<![if !supportLists]>18. <![endif]> └─rhel-import-state.service @4.342s +142ms
<![if !supportLists]>19. <![endif]> └─local-fs.target @4.324s
<![if !supportLists]>20. <![endif]> └─boot.mount @4.286s +31ms
<![if !supportLists]>21. <![endif]> └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.service @4.092s +149ms
<![if !supportLists]>22. <![endif]> └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4.092s
29. 获取某个服务（httpd）的依赖性列表
<![if !supportLists]>1. <![endif]># systemctl list-dependencies httpd.service
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>httpd.service
<![if !supportLists]>4. <![endif]>├─system.slice
<![if !supportLists]>5. <![endif]>└─basic.target
<![if !supportLists]>6. <![endif]> ├─firewalld.service
<![if !supportLists]>7. <![endif]> ├─microcode.service
<![if !supportLists]>8. <![endif]> ├─rhel-autorelabel-mark.service
<![if !supportLists]>9. <![endif]> ├─rhel-autorelabel.service
<![if !supportLists]>10. <![endif]> ├─rhel-configure.service
<![if !supportLists]>11. <![endif]> ├─rhel-dmesg.service
<![if !supportLists]>12. <![endif]> ├─rhel-loadmodules.service
<![if !supportLists]>13. <![endif]> ├─paths.target
<![if !supportLists]>14. <![endif]> ├─slices.target
<![if !supportLists]>15. <![endif]> │ ├─-.slice
<![if !supportLists]>16. <![endif]> │ └─system.slice
<![if !supportLists]>17. <![endif]> ├─sockets.target
<![if !supportLists]>18. <![endif]> │ ├─dbus.socket
<![if !supportLists]>19. <![endif]>….
30. 按等级列出控制组
<![if !supportLists]>1. <![endif]># systemd-cgls
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>├─1 /usr/lib/systemd/systemd –switched-root –system –deserialize 23
<![if !supportLists]>4. <![endif]>├─user.slice
<![if !supportLists]>5. <![endif]>│ └─user-0.slice
<![if !supportLists]>6. <![endif]>│ └─session-1.scope
<![if !supportLists]>7. <![endif]>│ ├─2498 sshd: root@pts/0
<![if !supportLists]>8. <![endif]>│ ├─2500 -bash
<![if !supportLists]>9. <![endif]>│ ├─4521 systemd-cgls
<![if !supportLists]>10. <![endif]>│ └─4522 systemd-cgls
<![if !supportLists]>11. <![endif]>└─system.slice
<![if !supportLists]>12. <![endif]> ├─httpd.service
<![if !supportLists]>13. <![endif]> │ ├─4440 /usr/sbin/httpd
-DFOREGROUND
<![if !supportLists]>14. <![endif]> │ ├─4442 /usr/sbin/httpd
-DFOREGROUND
<![if !supportLists]>15. <![endif]> │ ├─4443 /usr/sbin/httpd
-DFOREGROUND
<![if !supportLists]>16. <![endif]> │ ├─4444 /usr/sbin/httpd
-DFOREGROUND
<![if !supportLists]>17. <![endif]> │ ├─4445 /usr/sbin/httpd
-DFOREGROUND
<![if !supportLists]>18. <![endif]> │ └─4446 /usr/sbin/httpd
-DFOREGROUND
<![if !supportLists]>19. <![endif]> ├─polkit.service
<![if !supportLists]>20. <![endif]> │ └─721 /usr/lib/polkit-1/polkitd –no-debug
<![if !supportLists]>21. <![endif]>….
31. 按CPU、内存、输入和输出列出控制组
<![if !supportLists]>1. <![endif]># systemd-cgtop
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>Path
Tasks
%CPU Memory Input/s Output/s
<![if !supportLists]>4. <![endif]>
<![if !supportLists]>5. <![endif]>/
83 1.0 437.8M
- -
<![if !supportLists]>6. <![endif]>/system.slice
- 0.1
-
- -
<![if !supportLists]>7. <![endif]>/system.slice/mariadb.service
2 0.1
-
- -
<![if !supportLists]>8. <![endif]>/system.slice/tuned.service
1 0.0
-
- -
<![if !supportLists]>9. <![endif]>/system.slice/httpd.service
6 0.0
-
- -
<![if !supportLists]>10. <![endif]>/system.slice/NetworkManager.service
1 -
- - -
<![if !supportLists]>11. <![endif]>/system.slice/atop.service
1 -
- - -
<![if !supportLists]>12. <![endif]>/system.slice/atopacct.service
1 -
- - -
<![if !supportLists]>13. <![endif]>/system.slice/auditd.service
1 -
- - -
<![if !supportLists]>14. <![endif]>/system.slice/crond.service
1
-
- - -
<![if !supportLists]>15. <![endif]>/system.slice/dbus.service
1 -
- - -
<![if !supportLists]>16. <![endif]>/system.slice/firewalld.service
1 -
- - -
<![if !supportLists]>17. <![endif]>/system.slice/lvm2-lvmetad.service
1 -
- - -
<![if !supportLists]>18. <![endif]>/system.slice/polkit.service
1 -
- - -
<![if !supportLists]>19. <![endif]>/system.slice/postfix.service
3 -
- - -
<![if !supportLists]>20. <![endif]>/system.slice/rsyslog.service
1 -
- - -
<![if !supportLists]>21. <![endif]>/system.slice/system-getty.slice/getty@tty1.service
1 -
- - -
<![if !supportLists]>22. <![endif]>/system.slice/systemd-journald.service
1 -
- - -
<![if !supportLists]>23. <![endif]>/system.slice/systemd-logind.service
1 -
- - -
<![if !supportLists]>24. <![endif]>/system.slice/systemd-udevd.service
1 -
- - -
<![if !supportLists]>25. <![endif]>/system.slice/webmin.service
1 -
- - -
<![if !supportLists]>26. <![endif]>/user.slice/user-0.slice/session-1.scope
3 -
- - -
控制系统运行等级
32. 启动系统救援模式
<![if !supportLists]>1. <![endif]># systemctl rescue
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>Broadcast message from root@tecmint on pts/0 (Wed 2015-04-29 11:31:18 IST):
<![if !supportLists]>4. <![endif]>
<![if !supportLists]>5. <![endif]>The system is going down to rescue
mode NOW!
33. 进入紧急模式
<![if !supportLists]>1. <![endif]># systemctl emergency
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>Welcome to emergency mode! After
logging in, type "journalctl -xb" to
view
<![if !supportLists]>4. <![endif]>system logs, "systemctl reboot" to reboot, "systemctl
default" to try again
<![if !supportLists]>5. <![endif]>to boot into default mode.
34. 列出当前使用的运行等级
<![if !supportLists]>1. <![endif]># systemctl get-default
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]>multi-user.target
35. 启动运行等级5，即图形模式
<![if !supportLists]>1. <![endif]># systemctl isolate runlevel5.target
<![if !supportLists]>2. <![endif]>或
<![if !supportLists]>3. <![endif]># systemctl isolate graphical.target
36. 启动运行等级3，即多用户模式（命令行）
<![if !supportLists]>1. <![endif]># systemctl isolate runlevel3.target
<![if !supportLists]>2. <![endif]>或
<![if !supportLists]>3. <![endif]># systemctl isolate multiuser.target
36. 设置多用户模式或图形模式为默认运行等级
<![if !supportLists]>1. <![endif]># systemctl set-default runlevel3.target
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]># systemctl set-default runlevel5.target
37. 重启、停止、挂起、休眠系统或使系统进入混合睡眠
<![if !supportLists]>1. <![endif]># systemctl reboot
<![if !supportLists]>2. <![endif]>
<![if !supportLists]>3. <![endif]># systemctl halt
<![if !supportLists]>4. <![endif]>
<![if !supportLists]>5. <![endif]># systemctl suspend
<![if !supportLists]>6. <![endif]>
<![if !supportLists]>7. <![endif]># systemctl hibernate
<![if !supportLists]>8. <![endif]>
<![if !supportLists]>9. <![endif]># systemctl hybrid-sleep
对于不知运行等级为何物的人，说明如下。
<![if !supportLists]>·
<![endif]>Runlevel 0 : 关闭系统
<![if !supportLists]>·
<![endif]>Runlevel 1 : 救援？维护模式
<![if !supportLists]>·
<![endif]>Runlevel 3 : 多用户，无图形系统
<![if !supportLists]>·
<![endif]>Runlevel 4 : 多用户，无图形系统
<![if !supportLists]>·
<![endif]>Runlevel 5 : 多用户，图形化系统
<![if !supportLists]>·
<![endif]>Runlevel 6 : 关闭并重启机器