Error #0:
OMV\ExecException: Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C; omv-mkconf postfix 2>&1' with exit code '1': XMLStarlet Toolkit: Select from XML document(s)
Usage: xmlstarlet sel <global-options> {<template>} [ <xml-file> ... ]
where
  <global-options> - global options for selecting
  <xml-file> - input XML document file name/uri (stdin is used if missing)
  <template> - template for querying XML document with following syntax:

<global-options> are:
  -Q or --quiet             - do not write anything to standard output.
  -C or --comp              - display generated XSLT
  -R or --root              - print root element <xsl-select>
  -T or --text              - output is text (default is XML)
  -I or --indent            - indent output
  -D or --xml-decl          - do not omit xml declaration line
  -B or --noblanks          - remove insignificant spaces from XML tree
  -E or --encode <encoding> - output in the given encoding (utf-8, unicode...)
  -N <name>=<value>         - predefine namespaces (name without 'xmlns:')
                              ex: xsql=urn:oracle-xsql
                              Multiple -N options are allowed.
  --net                     - allow fetch DTDs or entities over network
  --help                    - display help

Syntax for templates: -t|--template <options>
where <options>
  -c or --copy-of <xpath>   - print copy of XPATH expression
  -v or --value-of <xpath>  - print value of XPATH expression
  -o or --output <string>   - output string literal
  -n or --nl                - print new line
  -f or --inp-name          - print input file name (or URL)
  -m or --match <xpath>     - match XPATH expression
  --var <name> <value> --break or
  --var <name>=<value>      - declare a variable (referenced by $name)
  -i or --if <test-xpath>   - check condition <xsl:if test="test-xpath">
  --elif <test-xpath>       - check condition if previous conditions failed
  --else                    - check if previous conditions failed
  -e or --elem <name>       - print out element <xsl:element name="name">
  -a or --attr <name>       - add attribute <xsl:attribute name="name">
  -b or --break             - break nesting
  -s or --sort op xpath     - sort in order (used after -m) where
  op is X:Y:Z,
      X is A - for order="ascending"
      X is D - for order="descending"
      Y is N - for data-type="numeric"
      Y is T - for data-type="text"
      Z is U - for case-order="upper-first"
      Z is L - for case-order="lower-first"

There can be multiple --match, --copy-of, --value-of, etc options
in a single template. The effect of applying command line templates
can be illustrated with the following XSLT analogue

xmlstarlet sel -t -c "xpath0" -m "xpath1" -m "xpath2" -v "xpath3" \
        -t -m "xpath4" -c "xpath5"

is equivalent to applying the following XSLT

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
  <xsl:call-template name="t1"/>
  <xsl:call-template name="t2"/>
</xsl:template>
<xsl:template name="t1">
  <xsl:copy-of select="xpath0"/>
  <xsl:for-each select="xpath1">
    <xsl:for-each select="xpath2">
      <xsl:value-of select="xpath3"/>
    </xsl:for-each>
  </xsl:for-each>
</xsl:template>
<xsl:template name="t2">
  <xsl:for-each select="xpath4">
    <xsl:copy-of select="xpath5"/>
  </xsl:for-each>
</xsl:template>
</xsl:stylesheet>

XMLStarlet is a command line toolkit to query/edit/check/transform
XML documents (for more information see http://xmlstar.sourceforge.net/)

Current implementation uses libxslt from GNOME codebase as XSLT processor
(see http://xmlsoft.org/ for more details)
run-parts: /usr/share/openmediavault/mkconf/postfix.d/10main exited with return code 2 in /usr/share/php/openmediavault/system/process.inc:175
Stack trace:
#0 /usr/share/openmediavault/engined/module/postfix.inc(47): OMV\System\Process->execute()
#1 /usr/share/openmediavault/engined/rpc/config.inc(168): OMVModulePostfix->applyConfig()
#2 [internal function]: OMVRpcServiceConfig->applyChanges(Array, Array)
#3 /usr/share/php/openmediavault/rpc/serviceabstract.inc(123): call_user_func_array(Array, Array)
#4 /usr/share/php/openmediavault/rpc/serviceabstract.inc(150): OMV\Rpc\ServiceAbstract->callMethod('applyChanges', Array, Array)
#5 /usr/share/php/openmediavault/rpc/serviceabstract.inc(528): OMV\Rpc\ServiceAbstract->OMV\Rpc\{closure}('/tmp/bgstatusee...', '/tmp/bgoutput6W...')
#6 /usr/share/php/openmediavault/rpc/serviceabstract.inc(151): OMV\Rpc\ServiceAbstract->execBgProc(Object(Closure))
#7 /usr/share/openmediavault/engined/rpc/config.inc(213): OMV\Rpc\ServiceAbstract->callMethodBg('applyChanges', Array, Array)
#8 [internal function]: OMVRpcServiceConfig->applyChangesBg(Array, Array)
#9 /usr/share/php/openmediavault/rpc/serviceabstract.inc(123): call_user_func_array(Array, Array)
#10 /usr/share/php/openmediavault/rpc/rpc.inc(86): OMV\Rpc\ServiceAbstract->callMethod('applyChangesBg', Array, Array)
#11 /usr/sbin/omv-engined(536): OMV\Rpc\Rpc::call('Config', 'applyChangesBg', Array, Array, 1)
#12 {main}