原链接：http://blog.pcwuyu.com/2015/630.html

原分类： Arch Linux, Linux

以下说明的是systemd-analyze的在分析系统启动性能的应用：

  1. $ systemd-analyze > starttime.txt 会在~/starttime.txt中显示启动时间。譬如[SSD中]：
Startup finished in 1.894s (kernel) + 5.970s (userspace) = 7.864s

2.$ systemd-analyze plot > start_time.svg 会在~/start_time.svg中显示启动项以及各自所消耗的时间，并在.svg中得到显示

imgimg

以下为man详解：

NAME

   systemd-analyze - Analyze system boot-up performance

SYNOPSIS

   systemd-analyze [OPTIONS...] [time]

   systemd-analyze [OPTIONS...] blame

   systemd-analyze [OPTIONS...] critical-chain [UNIT...]

   systemd-analyze [OPTIONS...] plot [> file.svg]

   systemd-analyze [OPTIONS...] dot [PATTERN...] [> file.dot]

   systemd-analyze [OPTIONS...] dump

   systemd-analyze [OPTIONS...] set-log-level [LEVEL]

   systemd-analyze [OPTIONS...] verify [FILES...]

DESCRIPTION

   systemd-analyze may be used to determine system boot-up performance statistics and retrieve other state and
   tracing information from the system and service manager, and to verify the correctness of unit files.

   systemd-analyze time prints the time spent in the kernel before userspace has been reached, the time spent
   in the initial RAM disk (initrd) before normal system userspace has been reached, and the time normal system
   userspace took to initialize. Note that these measurements simply measure the time passed up to the point
   where all system services have been spawned, but not necessarily until they fully finished initialization or
   the disk is idle.

   systemd-analyze blame prints a list of all running units, ordered by the time they took to initialize. This
   information may be used to optimize boot-up times. Note that the output might be misleading as the
   initialization of one service might be slow simply because it waits for the initialization of another
   service to complete.

   systemd-analyze critical-chain [UNIT...]  prints a tree of the time-critical chain of units (for each of the
   specified UNITs or for the default target otherwise). The time after the unit is active or started is
   printed after the "@" character. The time the unit takes to start is printed after the "+" character. Note
   that the output might be misleading as the initialization of one service might depend on socket activation
   and because of the parallel execution of units.

   systemd-analyze plot prints an SVG graphic detailing which system services have been started at what time,
   highlighting the time they spent on initialization.

   systemd-analyze dot generates textual dependency graph description in dot format for further processing with
   the GraphViz dot(1) tool. Use a command line like systemd-analyze dot | dot -Tsvg > systemd.svg to generate
   a graphical dependency tree. Unless --order or --require is passed, the generated graph will show both
   ordering and requirement dependencies. Optional pattern globbing style specifications (e.g.  *.target) may
   be given at the end. A unit dependency is included in the graph if any of these patterns match either the
   origin or destination node.

   systemd-analyze dump outputs a (usually very long) human-readable serialization of the complete server
   state. Its format is subject to change without notice and should not be parsed by applications.

   systemd-analyze set-log-level LEVEL changes the current log level of the systemd daemon to LEVEL (accepts
   the same values as --log-level= described in systemd(1)).

   systemd-analyze verify will load unit files and print warnings if any errors are detected. Files specified
   on the command line will be loaded, but also any other units referenced by them. This command works by
   prepending the directories for all command line arguments at the beginning of the unit load path, which
   means that all units files found in those directories will be used in preference to the unit files found in
   the standard locations, even if not listed explicitly.

   If no command is passed, systemd-analyze time is implied.

OPTIONS

   The following options are understood:

   --user
       Operates on the user systemd instance.

   --system
       Operates on the system systemd instance. This is the implied default.

   --order, --require
       When used in conjunction with the dot command (see above), selects which dependencies are shown in the
       dependency graph. If --order is passed, only dependencies of type After= or Before= are shown. If
       --require is passed, only dependencies of type Requires=, RequiresOverridable=, Requisite=,
       RequisiteOverridable=, Wants= and Conflicts= are shown. If neither is passed, this shows dependencies of
       all these types.

   --from-pattern=, --to-pattern=
       When used in conjunction with the dot command (see above), this selects which relationships are shown in
       the dependency graph. Both options require a glob(7) pattern as an argument, which will be matched
       against the left-hand and the right-hand, respectively, nodes of a relationship.

       Each of these can be used more than once, in which case the unit name must match one of the values. When
       tests for both sides of the relation are present, a relation must pass both tests to be shown. When
       patterns are also specified as positional arguments, they must match at least one side of the relation.
       In other words, patterns specified with those two options will trim the list of edges matched by the
       positional arguments, if any are given, and fully determine the list of edges shown otherwise.

   --fuzz=timespan
       When used in conjunction with the critical-chain command (see above), also show units, which finished
       timespan earlier, than the latest unit in the same level. The unit of timespan is seconds unless
       specified with a different unit, e.g. "50ms".

   --no-man
       Do not invoke man to verify the existence of man pages listed in Documentation=.

   -H, --host=
       Execute the operation remotely. Specify a hostname, or a username and hostname separated by "@", to
       connect to. The hostname may optionally be suffixed by a container name, separated by ":", which
       connects directly to a specific container on the specified host. This will use SSH to talk to the remote
       machine manager instance. Container names may be enumerated with machinectl -H HOST.

   -M, --machine=
       Execute operation on a local container. Specify a container name to connect to.

   -h, --help
       Print a short help text and exit.

   --version
       Print a short version string and exit.

   --no-pager
       Do not pipe output into a pager.

EXIT STATUS

   On success, 0 is returned, a non-zero failure code otherwise.

EXAMPLES FOR DOT

   Example 1. Plots all dependencies of any unit whose name starts with "avahi-daemon"

       $ systemd-analyze dot 'avahi-daemon.*' | dot -Tsvg > avahi.svg
             $ eog avahi.svg

   Example 2. Plots the dependencies between all known target units

       systemd-analyze dot --to-pattern='*.target' --from-pattern='*.target' | dot -Tsvg > targets.svg
       $ eog targets.svg

EXAMPLES FOR VERIFY

   The following errors are currently detected:

   ·   unknown sections and directives,

   ·   missing dependencies which are required to start the given unit,

   ·   man pages listed in Documentation= which are not found in the system,

   ·   commands listed in ExecStart= and similar which are not found in the system or not executable.

   Example 3. Misspelt directives

       $ cat ./user.slice
       [Unit]
       WhatIsThis=11
       Documentation=man:nosuchfile(1)
       Requires=different.service

       [Service]
       Desription=x

       $ systemd-analyze verify ./user.slice
       [./user.slice:9] Unknown lvalue 'WhatIsThis' in section 'Unit'
       [./user.slice:13] Unknown section 'Service'. Ignoring.
       Error: org.freedesktop.systemd1.LoadFailed:
          Unit different.service failed to load:
          No such file or directory.
       Failed to create user.slice/start: Invalid argument
       user.slice: man nosuchfile(1) command failed with code 16

   Example 4. Missing service units

       $ tail ./a.socket ./b.socket
       ==> ./a.socket <==
       [Socket]
       ListenStream=100

       ==> ./b.socket <==
       [Socket]
       ListenStream=100
       Accept=yes

       $ systemd-analyze verify ./a.socket ./b.socket
       Service a.service not loaded, a.socket cannot be started.
       Service [email protected] not loaded, b.socket cannot be started.

ENVIRONMENT

   $SYSTEMD_PAGER
       Pager to use when --no-pager is not given; overrides $PAGER. Setting this to an empty string or the
       value "cat" is equivalent to passing --no-pager.

   $SYSTEMD_LESS
       Override the default options passed to less ("FRSXMK").

SEE ALSO

   systemd(1), systemctl(1)