How to confirm if a system runs with rescue target in Red Hat Enterprise Linux 7

博客围绕Red Hat Enterprise Linux 7系统展开，提出如何确认系统是否以救援目标运行的问题。决议指出runlevel命令在systemd中仍可用，但runlevels是systemd中的遗留概念，通过'targets'模拟，且多个目标可同时激活，还给出确认当前运行级别的命令。

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SOLUTION 已验证 - 已更新 2014年一月16日11:48 -

English

环境

Red Hat Enterprise Linux 7

问题

How to confirm if a system runs with rescue target in Red Hat Enterprise Linux 7?

Raw

   The following description is found in man of runlevel command.
   ------------------------------------------------------------------------
    This is a legacy command available for compatibility only. It should
    not be used anymore, as the concept of runlevels is obsolete.
   ------------------------------------------------------------------------

决议

runlevel command still works with systemd. You can continue using that however runlevels is a legacy concept in systemd and is emulated via 'targets' and multiple targets can be active at the same time. You can confirm the current run level with the following command.

Raw

# systemctl list-units --type=target

< rescue mode >

~]# systemctl list-units --type=target
UNIT                LOAD   ACTIVE SUB    DESCRIPTION
basic.target        loaded active active Basic System
cryptsetup.target   loaded active active Encrypted Volumes
local-fs-pre.target loaded active active Local File Systems (Pre)
local-fs.target     loaded active active Local File Systems
paths.target        loaded active active Paths
rescue.target       loaded active active Rescue Mode <--- runlevel 1
slices.target       loaded active active Slices
sockets.target      loaded active active Sockets
swap.target         loaded active active Swap
sysinit.target      loaded active active System Initialization
timers.target       loaded active active Timers

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.

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

< run level 3 >

~]# systemctl list-units --type=target
UNIT                LOAD   ACTIVE SUB    DESCRIPTION
basic.target        loaded active active Basic System
cryptsetup.target   loaded active active Encrypted Volumes
getty.target        loaded active active Login Prompts
local-fs-pre.target loaded active active Local File Systems (Pre)
local-fs.target     loaded active active Local File Systems
multi-user.target   loaded active active Multi-User System <--- runlevel 3
network.target      loaded active active Network
nfs.target          loaded active active Network File System Server
paths.target        loaded active active Paths
remote-fs.target    loaded active active Remote File Systems
slices.target       loaded active active Slices
sockets.target      loaded active active Sockets
sound.target        loaded active active Sound Card
swap.target         loaded active active Swap
sysinit.target      loaded active active System Initialization
timers.target       loaded active active Timers

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.

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

如下是转帖者加的：

[postgres@server2 ~]$ systemctl list-units --type=target --all
  UNIT                   LOAD      ACTIVE   SUB    DESCRIPTION
  basic.target           loaded    active   active Basic System
  cryptsetup.target      loaded    active   active Encrypted Volumes
  emergency.target       loaded    inactive dead   Emergency Mode
  final.target           loaded    inactive dead   Final Step
  getty.target           loaded    active   active Login Prompts
  graphical.target       loaded    inactive dead   Graphical Interface
  local-fs-pre.target    loaded    active   active Local File Systems (Pre)
  local-fs.target        loaded    active   active Local File Systems
  multi-user.target      loaded    active   active Multi-User System
  network-online.target  loaded    active   active Network is Online
  network-pre.target     loaded    inactive dead   Network (Pre)
  network.target         loaded    active   active Network
  nss-lookup.target      loaded    inactive dead   Host and Network Name Lookups
  nss-user-lookup.target loaded    inactive dead   User and Group Name Lookups
  paths.target           loaded    active   active Paths
  remote-fs-pre.target   loaded    inactive dead   Remote File Systems (Pre)
  remote-fs.target       loaded    active   active Remote File Systems
  rescue.target          loaded    inactive dead   Rescue Mode
  shutdown.target        loaded    inactive dead   Shutdown
  slices.target          loaded    active   active Slices
  sockets.target         loaded    active   active Sockets
  swap.target            loaded    active   active Swap
  sysinit.target         loaded    active   active System Initialization
● syslog.target          not-found inactive dead   syslog.target
  time-sync.target       loaded    inactive dead   System Time Synchronized
  timers.target          loaded    active   active Timers
  umount.target          loaded    inactive dead   Unmount All Filesystems

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.

27 loaded units listed.
To show all installed unit files use 'systemctl list-unit-files'.
[postgres@server2 ~]$