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man: rebreak all of sd_notify(3)
No change of contents, just some rebreaking of the full file to match our current line break settings.
This commit is contained in:
Lennart Poettering
parent
75b29fda71
commit
1412ad9a81
@ -77,25 +77,20 @@
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<refsect1>
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<title>Description</title>
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<para><function>sd_notify()</function> may be called by a service
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to notify the service manager about state changes. It can be used
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to send arbitrary information, encoded in an
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environment-block-like string. Most importantly, it can be used for
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start-up completion notification.</para>
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<para>If the <parameter>unset_environment</parameter> parameter is
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non-zero, <function>sd_notify()</function> will unset the
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<varname>$NOTIFY_SOCKET</varname> environment variable before
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returning (regardless of whether the function call itself
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succeeded or not). Further calls to
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<function>sd_notify()</function> will then fail, but the variable
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is no longer inherited by child processes.</para>
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<para><function>sd_notify()</function> may be called by a service to notify the service manager about
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state changes. It can be used to send arbitrary information, encoded in an environment-block-like
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string. Most importantly, it can be used for start-up completion notification.</para>
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<para>The <parameter>state</parameter> parameter should contain a
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newline-separated list of variable assignments, similar in style
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to an environment block. A trailing newline is implied if none is
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specified. The string may contain any kind of variable
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assignments, but the following shall be considered
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<para>If the <parameter>unset_environment</parameter> parameter is non-zero,
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<function>sd_notify()</function> will unset the <varname>$NOTIFY_SOCKET</varname> environment variable
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before returning (regardless of whether the function call itself succeeded or not). Further calls to
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<function>sd_notify()</function> will then fail, but the variable is no longer inherited by child
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processes.</para>
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<para>The <parameter>state</parameter> parameter should contain a newline-separated list of variable
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assignments, similar in style to an environment block. A trailing newline is implied if none is
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specified. The string may contain any kind of variable assignments, but the following shall be considered
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well-known:</para>
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<variablelist>
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@ -136,102 +131,95 @@
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<varlistentry>
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<term>STOPPING=1</term>
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<listitem><para>Tells the service manager that the service is
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beginning its shutdown. This is useful to allow the service
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manager to track the service's internal state, and present it
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to the user.</para></listitem>
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<listitem><para>Tells the service manager that the service is beginning its shutdown. This is useful
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to allow the service manager to track the service's internal state, and present it to the
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user.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>STATUS=…</term>
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<listitem><para>Passes a single-line UTF-8 status string back
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to the service manager that describes the service state. This
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is free-form and can be used for various purposes: general
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state feedback, fsck-like programs could pass completion
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percentages and failing programs could pass a human-readable
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error message. Example: <literal>STATUS=Completed 66% of file
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system check…</literal></para></listitem>
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<listitem><para>Passes a single-line UTF-8 status string back to the service manager that describes
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the service state. This is free-form and can be used for various purposes: general state feedback,
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fsck-like programs could pass completion percentages and failing programs could pass a human-readable
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error message. Example: <literal>STATUS=Completed 66% of file system
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check…</literal></para></listitem>
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</varlistentry>
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<varlistentry>
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<term>NOTIFYACCESS=…</term>
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<listitem><para>Reset the access to the service status notification
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socket during runtime, overriding <varname>NotifyAccess=</varname> setting
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in the service unit file. See <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details, specifically <literal>NotifyAccess=</literal> for a list of
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accepted values.</para></listitem>
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<listitem><para>Reset the access to the service status notification socket during runtime, overriding
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<varname>NotifyAccess=</varname> setting in the service unit file. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details, specifically <literal>NotifyAccess=</literal> for a list of accepted
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values.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>ERRNO=…</term>
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<listitem><para>If a service fails, the errno-style error
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code, formatted as string. Example: <literal>ERRNO=2</literal>
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for ENOENT.</para></listitem>
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<listitem><para>If a service fails, the errno-style error code, formatted as string. Example:
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<literal>ERRNO=2</literal> for ENOENT.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>BUSERROR=…</term>
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<listitem><para>If a service fails, the D-Bus error-style
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error code. Example:
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<listitem><para>If a service fails, the D-Bus error-style error code. Example:
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<literal>BUSERROR=org.freedesktop.DBus.Error.TimedOut</literal></para></listitem>
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</varlistentry>
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<varlistentry>
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<term>MAINPID=…</term>
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<listitem><para>The main process ID (PID) of the service, in
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case the service manager did not fork off the process itself.
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Example: <literal>MAINPID=4711</literal></para></listitem>
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<listitem><para>The main process ID (PID) of the service, in case the service manager did not fork
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off the process itself. Example: <literal>MAINPID=4711</literal></para></listitem>
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</varlistentry>
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<varlistentry>
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<term>WATCHDOG=1</term>
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<listitem><para>Tells the service manager to update the
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watchdog timestamp. This is the keep-alive ping that services
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need to issue in regular intervals if
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<varname>WatchdogSec=</varname> is enabled for it. See
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<listitem><para>Tells the service manager to update the watchdog timestamp. This is the keep-alive
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ping that services need to issue in regular intervals if <varname>WatchdogSec=</varname> is enabled
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for it. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for information how to enable this functionality and
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<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for the details of how the service can check whether the
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watchdog is enabled. </para></listitem>
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for the details of how the service can check whether the watchdog is enabled. </para></listitem>
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</varlistentry>
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<varlistentry>
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<term>WATCHDOG=trigger</term>
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<listitem><para>Tells the service manager that the service detected an internal error that should be handled by
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the configured watchdog options. This will trigger the same behaviour as if <varname>WatchdogSec=</varname> is
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enabled and the service did not send <literal>WATCHDOG=1</literal> in time. Note that
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<varname>WatchdogSec=</varname> does not need to be enabled for <literal>WATCHDOG=trigger</literal> to trigger
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the watchdog action. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
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information about the watchdog behavior. </para></listitem>
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<listitem><para>Tells the service manager that the service detected an internal error that should be
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handled by the configured watchdog options. This will trigger the same behaviour as if
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<varname>WatchdogSec=</varname> is enabled and the service did not send <literal>WATCHDOG=1</literal>
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in time. Note that <varname>WatchdogSec=</varname> does not need to be enabled for
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<literal>WATCHDOG=trigger</literal> to trigger the watchdog action. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for information about the watchdog behavior. </para></listitem>
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</varlistentry>
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<varlistentry>
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<term>WATCHDOG_USEC=…</term>
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<listitem><para>Reset <varname>watchdog_usec</varname> value during runtime.
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Notice that this is not available when using <function>sd_event_set_watchdog()</function>
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or <function>sd_watchdog_enabled()</function>.
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Example : <literal>WATCHDOG_USEC=20000000</literal></para></listitem>
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<listitem><para>Reset <varname>watchdog_usec</varname> value during runtime. Notice that this is not
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available when using <function>sd_event_set_watchdog()</function> or
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<function>sd_watchdog_enabled()</function>. Example :
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<literal>WATCHDOG_USEC=20000000</literal></para></listitem>
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</varlistentry>
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<varlistentry>
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<term>EXTEND_TIMEOUT_USEC=…</term>
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<listitem><para>Tells the service manager to extend the startup, runtime or shutdown service timeout
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corresponding the current state. The value specified is a time in microseconds during which the service must
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send a new message. A service timeout will occur if the message isn't received, but only if the runtime of the
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current state is beyond the original maximum times of <varname>TimeoutStartSec=</varname>, <varname>RuntimeMaxSec=</varname>,
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and <varname>TimeoutStopSec=</varname>.
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See <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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corresponding the current state. The value specified is a time in microseconds during which the
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service must send a new message. A service timeout will occur if the message isn't received, but only
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if the runtime of the current state is beyond the original maximum times of
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<varname>TimeoutStartSec=</varname>, <varname>RuntimeMaxSec=</varname>, and
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<varname>TimeoutStopSec=</varname>. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for effects on the service timeouts.</para></listitem>
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</varlistentry>
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@ -266,33 +254,37 @@
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<varlistentry>
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<term>FDSTOREREMOVE=1</term>
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<listitem><para>Removes file descriptors from the file descriptor store. This field needs to be combined with
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<varname>FDNAME=</varname> to specify the name of the file descriptors to remove.</para></listitem>
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<listitem><para>Removes file descriptors from the file descriptor store. This field needs to be
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combined with <varname>FDNAME=</varname> to specify the name of the file descriptors to
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remove.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>FDNAME=…</term>
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<listitem><para>When used in combination with <varname>FDSTORE=1</varname>, specifies a name for the submitted
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file descriptors. When used with <varname>FDSTOREREMOVE=1</varname>, specifies the name for the file
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descriptors to remove. This name is passed to the service during activation, and may be queried using
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<listitem><para>When used in combination with <varname>FDSTORE=1</varname>, specifies a name for the
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submitted file descriptors. When used with <varname>FDSTOREREMOVE=1</varname>, specifies the name for
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the file descriptors to remove. This name is passed to the service during activation, and may be
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queried using
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<citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry>. File
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descriptors submitted without this field set, will implicitly get the name <literal>stored</literal>
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assigned. Note that, if multiple file descriptors are submitted at once, the specified name will be assigned to
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all of them. In order to assign different names to submitted file descriptors, submit them in separate
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invocations of <function>sd_pid_notify_with_fds()</function>. The name may consist of arbitrary ASCII
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characters except control characters or <literal>:</literal>. It may not be longer than 255 characters. If a
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submitted name does not follow these restrictions, it is ignored.</para></listitem>
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assigned. Note that, if multiple file descriptors are submitted at once, the specified name will be
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assigned to all of them. In order to assign different names to submitted file descriptors, submit
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them in separate invocations of <function>sd_pid_notify_with_fds()</function>. The name may consist
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of arbitrary ASCII characters except control characters or <literal>:</literal>. It may not be longer
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than 255 characters. If a submitted name does not follow these restrictions, it is
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ignored.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>FDPOLL=0</term>
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<listitem><para>When used in combination with <varname>FDSTORE=1</varname>, disables polling of the stored
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file descriptors regardless of whether or not they are pollable. As this option disables automatic cleanup
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of the stored file descriptors on EPOLLERR and EPOLLHUP, care must be taken to ensure proper manual cleanup.
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Use of this option is not generally recommended except for when automatic cleanup has unwanted behavior such
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as prematurely discarding file descriptors from the store.</para></listitem>
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<listitem><para>When used in combination with <varname>FDSTORE=1</varname>, disables polling of the
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stored file descriptors regardless of whether or not they are pollable. As this option disables
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automatic cleanup of the stored file descriptors on EPOLLERR and EPOLLHUP, care must be taken to
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ensure proper manual cleanup. Use of this option is not generally recommended except for when
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automatic cleanup has unwanted behavior such as prematurely discarding file descriptors from the
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store.</para></listitem>
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</varlistentry>
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<varlistentry>
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@ -309,23 +301,22 @@
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</varlistentry>
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</variablelist>
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<para>It is recommended to prefix variable names that are not
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listed above with <varname>X_</varname> to avoid namespace
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clashes.</para>
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<para>It is recommended to prefix variable names that are not listed above with <varname>X_</varname> to
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avoid namespace clashes.</para>
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<para>Note that systemd will accept status data sent from a
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service only if the <varname>NotifyAccess=</varname> option is
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correctly set in the service definition file. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details.</para>
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<para>Note that systemd will accept status data sent from a service only if the
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<varname>NotifyAccess=</varname> option is correctly set in the service definition file. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
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details.</para>
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<para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
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the sending process is still around at the time PID 1 processes the message, or if the sending process is
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explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
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off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
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<varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
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<function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
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attribute the message to the unit, and thus will ignore it, even if
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<para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only
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if either the sending process is still around at the time PID 1 processes the message, or if the sending
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process is explicitly runtime-tracked by the service manager. The latter is the case if the service
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manager originally forked off the process, i.e. on all processes that match
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<varname>NotifyAccess=</varname><option>main</option> or
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<varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit
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sends an <function>sd_notify()</function> message and immediately exits, the service manager might not be
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able to properly attribute the message to the unit, and thus will ignore it, even if
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<varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
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<para>Hence, to eliminate all race conditions involving lookup of the client's unit and attribution of notifications
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@ -335,22 +326,15 @@
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service manager, otherwise this synchronization mechanism is unnecessary for attribution of notifications to the
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unit.</para>
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<para><function>sd_notifyf()</function> is similar to
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<function>sd_notify()</function> but takes a
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<function>printf()</function>-like format string plus
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arguments.</para>
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<para><function>sd_notifyf()</function> is similar to <function>sd_notify()</function> but takes a
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<function>printf()</function>-like format string plus arguments.</para>
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<para><function>sd_pid_notify()</function> and
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<function>sd_pid_notifyf()</function> are similar to
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<function>sd_notify()</function> and
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<function>sd_notifyf()</function> but take a process ID (PID) to
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use as originating PID for the message as first argument. This is
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useful to send notification messages on behalf of other processes,
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provided the appropriate privileges are available. If the PID
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argument is specified as 0, the process ID of the calling process
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is used, in which case the calls are fully equivalent to
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<function>sd_notify()</function> and
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<function>sd_notifyf()</function>.</para>
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<para><function>sd_pid_notify()</function> and <function>sd_pid_notifyf()</function> are similar to
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<function>sd_notify()</function> and <function>sd_notifyf()</function> but take a process ID (PID) to use
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as originating PID for the message as first argument. This is useful to send notification messages on
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behalf of other processes, provided the appropriate privileges are available. If the PID argument is
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specified as 0, the process ID of the calling process is used, in which case the calls are fully
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equivalent to <function>sd_notify()</function> and <function>sd_notifyf()</function>.</para>
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<para><function>sd_pid_notify_with_fds()</function> is similar to <function>sd_pid_notify()</function>
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but takes an additional array of file descriptors. These file descriptors are sent along the notification
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@ -361,10 +345,9 @@
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that file descriptors sent to the service manager on a message without <literal>FDSTORE=1</literal> are
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immediately closed on reception.</para>
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<para><function>sd_notify_barrier()</function> allows the caller to
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synchronize against reception of previously sent notification messages
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and uses the <varname>BARRIER=1</varname> command. It takes a relative
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<varname>timeout</varname> value in microseconds which is passed to
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<para><function>sd_notify_barrier()</function> allows the caller to synchronize against reception of
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previously sent notification messages and uses the <varname>BARRIER=1</varname> command. It takes a
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relative <varname>timeout</varname> value in microseconds which is passed to
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<citerefentry><refentrytitle>ppoll</refentrytitle><manvolnum>2</manvolnum>
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</citerefentry>. A value of UINT64_MAX is interpreted as infinite timeout.
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</para>
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@ -373,14 +356,15 @@
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<refsect1>
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<title>Return Value</title>
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<para>On failure, these calls return a negative errno-style error code. If <varname>$NOTIFY_SOCKET</varname> was
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not set and hence no status message could be sent, 0 is returned. If the status was sent, these functions return a
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positive value. In order to support both service managers that implement this scheme and those which do not, it is
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generally recommended to ignore the return value of this call. Note that the return value simply indicates whether
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the notification message was enqueued properly, it does not reflect whether the message could be processed
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<para>On failure, these calls return a negative errno-style error code. If
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<varname>$NOTIFY_SOCKET</varname> was not set and hence no status message could be sent, 0 is
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returned. If the status was sent, these functions return a positive value. In order to support both
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service managers that implement this scheme and those which do not, it is generally recommended to ignore
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the return value of this call. Note that the return value simply indicates whether the notification
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message was enqueued properly, it does not reflect whether the message could be processed
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successfully. Specifically, no error is returned when a file descriptor is attempted to be stored using
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<varname>FDSTORE=1</varname> but the service is not actually configured to permit storing of file descriptors (see
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above).</para>
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<varname>FDSTORE=1</varname> but the service is not actually configured to permit storing of file
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descriptors (see above).</para>
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</refsect1>
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<refsect1>
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@ -389,27 +373,21 @@
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<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
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<xi:include href="threads-aware.xml" xpointer="getenv"/>
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<para>These functions send a single datagram with the
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state string as payload to the socket referenced in the
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<varname>$NOTIFY_SOCKET</varname> environment variable. If the
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first character of <varname>$NOTIFY_SOCKET</varname> is
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<literal>/</literal> or <literal>@</literal>, the string is understood
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||||
as an <constant>AF_UNIX</constant> or Linux abstract namespace socket
|
||||
(respectively), and in both cases the datagram is accompanied by the
|
||||
process credentials of the sending service, using SCM_CREDENTIALS. If
|
||||
the string starts with <literal>vsock:</literal> then the string is
|
||||
understood as an <constant>AF_VSOCK</constant> address, which is useful
|
||||
for hypervisors/VMMs or other processes on the host to receive a
|
||||
notification when a virtual machine has finished booting. Note that in
|
||||
case the hypervisor does not support <constant>SOCK_DGRAM</constant>
|
||||
over <constant>AF_VSOCK</constant>, <constant>SOCK_SEQPACKET</constant>
|
||||
will be used instead. The address should be in the form:
|
||||
<literal>vsock:CID:PORT</literal>. Note that unlike other uses of vsock,
|
||||
the CID is mandatory and cannot be <literal>VMADDR_CID_ANY</literal>.
|
||||
Note that PID1 will send the VSOCK packets from a privileged port
|
||||
(i.e.: lower than 1024), as an attempt to address concerns that unprivileged
|
||||
processes in the guest might try to send malicious notifications to the
|
||||
host, driving it to make destructive decisions based on them.</para>
|
||||
<para>These functions send a single datagram with the state string as payload to the socket referenced in
|
||||
the <varname>$NOTIFY_SOCKET</varname> environment variable. If the first character of
|
||||
<varname>$NOTIFY_SOCKET</varname> is <literal>/</literal> or <literal>@</literal>, the string is
|
||||
understood as an <constant>AF_UNIX</constant> or Linux abstract namespace socket (respectively), and in
|
||||
both cases the datagram is accompanied by the process credentials of the sending service, using
|
||||
SCM_CREDENTIALS. If the string starts with <literal>vsock:</literal> then the string is understood as an
|
||||
<constant>AF_VSOCK</constant> address, which is useful for hypervisors/VMMs or other processes on the
|
||||
host to receive a notification when a virtual machine has finished booting. Note that in case the
|
||||
hypervisor does not support <constant>SOCK_DGRAM</constant> over <constant>AF_VSOCK</constant>,
|
||||
<constant>SOCK_SEQPACKET</constant> will be used instead. The address should be in the form:
|
||||
<literal>vsock:CID:PORT</literal>. Note that unlike other uses of vsock, the CID is mandatory and cannot
|
||||
be <literal>VMADDR_CID_ANY</literal>. Note that PID1 will send the VSOCK packets from a privileged port
|
||||
(i.e.: lower than 1024), as an attempt to address concerns that unprivileged processes in the guest might
|
||||
try to send malicious notifications to the host, driving it to make destructive decisions based on
|
||||
them.</para>
|
||||
</refsect1>
|
||||
|
||||
<refsect1>
|
||||
@ -419,11 +397,9 @@
|
||||
<varlistentry>
|
||||
<term><varname>$NOTIFY_SOCKET</varname></term>
|
||||
|
||||
<listitem><para>Set by the service manager for supervised
|
||||
processes for status and start-up completion notification.
|
||||
This environment variable specifies the socket
|
||||
<function>sd_notify()</function> talks to. See above for
|
||||
details.</para></listitem>
|
||||
<listitem><para>Set by the service manager for supervised processes for status and start-up
|
||||
completion notification. This environment variable specifies the socket
|
||||
<function>sd_notify()</function> talks to. See above for details.</para></listitem>
|
||||
</varlistentry>
|
||||
</variablelist>
|
||||
</refsect1>
|
||||
@ -434,8 +410,8 @@
|
||||
<example>
|
||||
<title>Start-up Notification</title>
|
||||
|
||||
<para>When a service finished starting up, it might issue the
|
||||
following call to notify the service manager:</para>
|
||||
<para>When a service finished starting up, it might issue the following call to notify the service
|
||||
manager:</para>
|
||||
|
||||
<programlisting>sd_notify(0, "READY=1");</programlisting>
|
||||
</example>
|
||||
@ -443,8 +419,7 @@
|
||||
<example>
|
||||
<title>Extended Start-up Notification</title>
|
||||
|
||||
<para>A service could send the following after completing
|
||||
initialization:</para>
|
||||
<para>A service could send the following after completing initialization:</para>
|
||||
|
||||
<programlisting>
|
||||
sd_notifyf(0, "READY=1\n"
|
||||
@ -468,9 +443,8 @@ sd_notifyf(0, "STATUS=Failed to start up: %s\n"
|
||||
<example>
|
||||
<title>Store a File Descriptor in the Service Manager</title>
|
||||
|
||||
<para>To store an open file descriptor in the service manager,
|
||||
in order to continue operation after a service restart without
|
||||
losing state, use <literal>FDSTORE=1</literal>:</para>
|
||||
<para>To store an open file descriptor in the service manager, in order to continue operation after a
|
||||
service restart without losing state, use <literal>FDSTORE=1</literal>:</para>
|
||||
|
||||
<programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1\nFDNAME=foobar", &fd, 1);</programlisting>
|
||||
</example>
|
||||
@ -478,12 +452,10 @@ sd_notifyf(0, "STATUS=Failed to start up: %s\n"
|
||||
<example>
|
||||
<title>Eliminating race conditions</title>
|
||||
|
||||
<para>When the client sending the notifications is not spawned
|
||||
by the service manager, it may exit too quickly and the service
|
||||
manager may fail to attribute them correctly to the unit. To
|
||||
prevent such races, use <function>sd_notify_barrier()</function>
|
||||
to synchronize against reception of all notifications sent before
|
||||
this call is made.</para>
|
||||
<para>When the client sending the notifications is not spawned by the service manager, it may exit too
|
||||
quickly and the service manager may fail to attribute them correctly to the unit. To prevent such
|
||||
races, use <function>sd_notify_barrier()</function> to synchronize against reception of all
|
||||
notifications sent before this call is made.</para>
|
||||
|
||||
<programlisting>
|
||||
sd_notify(0, "READY=1");
|
||||
|
||||
Loading…
Reference in New Issue
Block a user