mirror of
https://github.com/chylex/Nextcloud-Desktop.git
synced 2024-10-19 04:42:46 +02:00
1120 lines
33 KiB
HTML
1120 lines
33 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
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"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
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<head>
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<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
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<meta name="generator" content="AsciiDoc 8.6.6" />
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<title>CSYNC User Guide</title>
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<style type="text/css">
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/* Shared CSS for AsciiDoc xhtml11 and html5 backends */
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/* Default font. */
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body {
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font-family: Georgia,serif;
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}
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/* Title font. */
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h1, h2, h3, h4, h5, h6,
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div.title, caption.title,
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thead, p.table.header,
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#toctitle,
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#author, #revnumber, #revdate, #revremark,
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#footer {
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font-family: Arial,Helvetica,sans-serif;
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}
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body {
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margin: 1em 5% 1em 5%;
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}
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a {
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color: blue;
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text-decoration: underline;
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}
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a:visited {
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color: fuchsia;
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}
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em {
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font-style: italic;
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color: navy;
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}
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strong {
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font-weight: bold;
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color: #083194;
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}
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h1, h2, h3, h4, h5, h6 {
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color: #527bbd;
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margin-top: 1.2em;
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margin-bottom: 0.5em;
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line-height: 1.3;
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}
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h1, h2, h3 {
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border-bottom: 2px solid silver;
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}
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h2 {
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padding-top: 0.5em;
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}
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h3 {
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float: left;
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}
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h3 + * {
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clear: left;
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}
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h5 {
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font-size: 1.0em;
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}
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div.sectionbody {
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margin-left: 0;
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}
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hr {
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border: 1px solid silver;
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}
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p {
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margin-top: 0.5em;
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margin-bottom: 0.5em;
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}
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ul, ol, li > p {
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margin-top: 0;
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}
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ul > li { color: #aaa; }
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ul > li > * { color: black; }
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pre {
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padding: 0;
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margin: 0;
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}
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#author {
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color: #527bbd;
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font-weight: bold;
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font-size: 1.1em;
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}
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#email {
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}
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#revnumber, #revdate, #revremark {
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}
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#footer {
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font-size: small;
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border-top: 2px solid silver;
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padding-top: 0.5em;
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margin-top: 4.0em;
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}
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#footer-text {
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float: left;
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padding-bottom: 0.5em;
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}
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#footer-badges {
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float: right;
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padding-bottom: 0.5em;
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}
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#preamble {
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margin-top: 1.5em;
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margin-bottom: 1.5em;
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}
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div.imageblock, div.exampleblock, div.verseblock,
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div.quoteblock, div.literalblock, div.listingblock, div.sidebarblock,
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div.admonitionblock {
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margin-top: 1.0em;
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margin-bottom: 1.5em;
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}
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div.admonitionblock {
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margin-top: 2.0em;
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margin-bottom: 2.0em;
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margin-right: 10%;
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color: #606060;
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}
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div.content { /* Block element content. */
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padding: 0;
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}
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/* Block element titles. */
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div.title, caption.title {
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color: #527bbd;
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font-weight: bold;
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text-align: left;
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margin-top: 1.0em;
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margin-bottom: 0.5em;
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}
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div.title + * {
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margin-top: 0;
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}
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td div.title:first-child {
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margin-top: 0.0em;
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}
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div.content div.title:first-child {
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margin-top: 0.0em;
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}
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div.content + div.title {
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margin-top: 0.0em;
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}
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div.sidebarblock > div.content {
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background: #ffffee;
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border: 1px solid #dddddd;
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border-left: 4px solid #f0f0f0;
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padding: 0.5em;
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}
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div.listingblock > div.content {
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border: 1px solid #dddddd;
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border-left: 5px solid #f0f0f0;
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background: #f8f8f8;
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padding: 0.5em;
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}
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div.quoteblock, div.verseblock {
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padding-left: 1.0em;
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margin-left: 1.0em;
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margin-right: 10%;
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border-left: 5px solid #f0f0f0;
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color: #888;
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}
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div.quoteblock > div.attribution {
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padding-top: 0.5em;
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text-align: right;
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}
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div.verseblock > pre.content {
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font-family: inherit;
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font-size: inherit;
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}
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div.verseblock > div.attribution {
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padding-top: 0.75em;
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text-align: left;
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}
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/* DEPRECATED: Pre version 8.2.7 verse style literal block. */
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div.verseblock + div.attribution {
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text-align: left;
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}
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div.admonitionblock .icon {
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vertical-align: top;
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font-size: 1.1em;
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font-weight: bold;
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text-decoration: underline;
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color: #527bbd;
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padding-right: 0.5em;
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}
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div.admonitionblock td.content {
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padding-left: 0.5em;
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border-left: 3px solid #dddddd;
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}
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div.exampleblock > div.content {
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border-left: 3px solid #dddddd;
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padding-left: 0.5em;
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}
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div.imageblock div.content { padding-left: 0; }
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span.image img { border-style: none; }
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a.image:visited { color: white; }
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dl {
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margin-top: 0.8em;
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margin-bottom: 0.8em;
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}
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dt {
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margin-top: 0.5em;
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margin-bottom: 0;
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font-style: normal;
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color: navy;
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}
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dd > *:first-child {
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margin-top: 0.1em;
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}
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ul, ol {
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list-style-position: outside;
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}
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ol.arabic {
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list-style-type: decimal;
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}
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ol.loweralpha {
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list-style-type: lower-alpha;
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}
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ol.upperalpha {
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list-style-type: upper-alpha;
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}
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ol.lowerroman {
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list-style-type: lower-roman;
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}
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ol.upperroman {
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list-style-type: upper-roman;
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}
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div.compact ul, div.compact ol,
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div.compact p, div.compact p,
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div.compact div, div.compact div {
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margin-top: 0.1em;
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margin-bottom: 0.1em;
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}
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tfoot {
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font-weight: bold;
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}
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td > div.verse {
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white-space: pre;
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}
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div.hdlist {
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margin-top: 0.8em;
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margin-bottom: 0.8em;
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}
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div.hdlist tr {
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padding-bottom: 15px;
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}
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dt.hdlist1.strong, td.hdlist1.strong {
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font-weight: bold;
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}
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td.hdlist1 {
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vertical-align: top;
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font-style: normal;
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padding-right: 0.8em;
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color: navy;
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}
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td.hdlist2 {
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vertical-align: top;
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}
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div.hdlist.compact tr {
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margin: 0;
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padding-bottom: 0;
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}
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.comment {
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background: yellow;
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}
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.footnote, .footnoteref {
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font-size: 0.8em;
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}
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span.footnote, span.footnoteref {
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vertical-align: super;
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}
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#footnotes {
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margin: 20px 0 20px 0;
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padding: 7px 0 0 0;
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}
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#footnotes div.footnote {
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margin: 0 0 5px 0;
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}
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#footnotes hr {
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border: none;
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border-top: 1px solid silver;
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height: 1px;
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text-align: left;
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margin-left: 0;
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width: 20%;
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min-width: 100px;
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}
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div.colist td {
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padding-right: 0.5em;
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padding-bottom: 0.3em;
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vertical-align: top;
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}
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div.colist td img {
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margin-top: 0.3em;
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}
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@media print {
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#footer-badges { display: none; }
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}
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#toc {
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margin-bottom: 2.5em;
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}
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#toctitle {
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color: #527bbd;
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font-size: 1.1em;
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font-weight: bold;
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margin-top: 1.0em;
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margin-bottom: 0.1em;
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}
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div.toclevel1, div.toclevel2, div.toclevel3, div.toclevel4 {
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margin-top: 0;
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margin-bottom: 0;
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}
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div.toclevel2 {
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margin-left: 2em;
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font-size: 0.9em;
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}
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div.toclevel3 {
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margin-left: 4em;
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font-size: 0.9em;
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}
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div.toclevel4 {
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margin-left: 6em;
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font-size: 0.9em;
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}
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span.aqua { color: aqua; }
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span.black { color: black; }
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span.blue { color: blue; }
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span.fuchsia { color: fuchsia; }
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span.gray { color: gray; }
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span.green { color: green; }
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span.lime { color: lime; }
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span.maroon { color: maroon; }
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span.navy { color: navy; }
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span.olive { color: olive; }
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span.purple { color: purple; }
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span.red { color: red; }
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span.silver { color: silver; }
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span.teal { color: teal; }
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span.white { color: white; }
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span.yellow { color: yellow; }
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span.aqua-background { background: aqua; }
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span.black-background { background: black; }
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span.blue-background { background: blue; }
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span.fuchsia-background { background: fuchsia; }
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span.gray-background { background: gray; }
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span.green-background { background: green; }
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span.lime-background { background: lime; }
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span.maroon-background { background: maroon; }
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span.navy-background { background: navy; }
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span.olive-background { background: olive; }
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span.purple-background { background: purple; }
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span.red-background { background: red; }
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span.silver-background { background: silver; }
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span.teal-background { background: teal; }
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span.white-background { background: white; }
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span.yellow-background { background: yellow; }
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span.big { font-size: 2em; }
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span.small { font-size: 0.6em; }
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span.underline { text-decoration: underline; }
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span.overline { text-decoration: overline; }
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span.line-through { text-decoration: line-through; }
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/*
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* xhtml11 specific
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*
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* */
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tt {
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font-family: monospace;
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font-size: inherit;
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color: navy;
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}
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div.tableblock {
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margin-top: 1.0em;
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margin-bottom: 1.5em;
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}
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div.tableblock > table {
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border: 3px solid #527bbd;
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}
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thead, p.table.header {
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font-weight: bold;
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color: #527bbd;
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}
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p.table {
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margin-top: 0;
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}
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/* Because the table frame attribute is overriden by CSS in most browsers. */
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div.tableblock > table[frame="void"] {
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border-style: none;
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}
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div.tableblock > table[frame="hsides"] {
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border-left-style: none;
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border-right-style: none;
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}
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div.tableblock > table[frame="vsides"] {
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border-top-style: none;
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border-bottom-style: none;
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}
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/*
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* html5 specific
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*
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* */
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.monospaced {
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font-family: monospace;
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font-size: inherit;
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color: navy;
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}
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table.tableblock {
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margin-top: 1.0em;
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margin-bottom: 1.5em;
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}
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thead, p.tableblock.header {
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font-weight: bold;
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color: #527bbd;
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}
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p.tableblock {
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margin-top: 0;
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}
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table.tableblock {
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border-width: 3px;
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border-spacing: 0px;
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border-style: solid;
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border-color: #527bbd;
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border-collapse: collapse;
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}
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th.tableblock, td.tableblock {
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border-width: 1px;
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padding: 4px;
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border-style: solid;
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border-color: #527bbd;
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}
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table.tableblock.frame-topbot {
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border-left-style: hidden;
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border-right-style: hidden;
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}
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table.tableblock.frame-sides {
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border-top-style: hidden;
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border-bottom-style: hidden;
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}
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table.tableblock.frame-none {
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border-style: hidden;
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}
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th.tableblock.halign-left, td.tableblock.halign-left {
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text-align: left;
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}
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th.tableblock.halign-center, td.tableblock.halign-center {
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text-align: center;
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}
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th.tableblock.halign-right, td.tableblock.halign-right {
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text-align: right;
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}
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th.tableblock.valign-top, td.tableblock.valign-top {
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vertical-align: top;
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}
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th.tableblock.valign-middle, td.tableblock.valign-middle {
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vertical-align: middle;
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}
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th.tableblock.valign-bottom, td.tableblock.valign-bottom {
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vertical-align: bottom;
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}
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|
|
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|
/*
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* manpage specific
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*
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* */
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|
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body.manpage h1 {
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padding-top: 0.5em;
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padding-bottom: 0.5em;
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border-top: 2px solid silver;
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border-bottom: 2px solid silver;
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}
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|
body.manpage h2 {
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border-style: none;
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}
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|
body.manpage div.sectionbody {
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margin-left: 3em;
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}
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|
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@media print {
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|
body.manpage div#toc { display: none; }
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}
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|
</style>
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|
<script type="text/javascript">
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|
/*<+'])');
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// Function that scans the DOM tree for header elements (the DOM2
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|
// nodeIterator API would be a better technique but not supported by all
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|
// browsers).
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|
var iterate = function (el) {
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|
for (var i = el.firstChild; i != null; i = i.nextSibling) {
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|
if (i.nodeType == 1 /* Node.ELEMENT_NODE */) {
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|
var mo = re.exec(i.tagName);
|
|
if (mo && (i.getAttribute("class") || i.getAttribute("className")) != "float") {
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result[result.length] = new TocEntry(i, getText(i), mo[1]-1);
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}
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|
iterate(i);
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|
}
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|
}
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|
}
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|
iterate(el);
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return result;
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}
|
|
|
|
var toc = document.getElementById("toc");
|
|
if (!toc) {
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return;
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}
|
|
|
|
// Delete existing TOC entries in case we're reloading the TOC.
|
|
var tocEntriesToRemove = [];
|
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var i;
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for (i = 0; i < toc.childNodes.length; i++) {
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var entry = toc.childNodes[i];
|
|
if (entry.nodeName == 'div'
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&& entry.getAttribute("class")
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&& entry.getAttribute("class").match(/^toclevel/))
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tocEntriesToRemove.push(entry);
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}
|
|
for (i = 0; i < tocEntriesToRemove.length; i++) {
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toc.removeChild(tocEntriesToRemove[i]);
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}
|
|
|
|
// Rebuild TOC entries.
|
|
var entries = tocEntries(document.getElementById("content"), toclevels);
|
|
for (var i = 0; i < entries.length; ++i) {
|
|
var entry = entries[i];
|
|
if (entry.element.id == "")
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|
entry.element.id = "_toc_" + i;
|
|
var a = document.createElement("a");
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</head>
|
|
<body class="article">
|
|
<div id="header">
|
|
<h1>CSYNC User Guide</h1>
|
|
<span id="author">Andreas Schneider</span><br />
|
|
<span id="email"><tt><<a href="mailto:asn@cryptomilk.org">asn@cryptomilk.org</a>></tt></span><br />
|
|
<div id="toc">
|
|
<div id="toctitle">Table of Contents</div>
|
|
<noscript><p><b>JavaScript must be enabled in your browser to display the table of contents.</b></p></noscript>
|
|
</div>
|
|
</div>
|
|
<div id="content">
|
|
<div id="preamble">
|
|
<div class="sectionbody">
|
|
<div class="paragraph"><p>csync is a lightweight utility to synchronize files between two directories
|
|
on a system or between multiple systems.</p></div>
|
|
<div class="paragraph"><p>It synchronizes bidirectionally and allows the user to keep two copies of files
|
|
and directories in sync. csync uses widely adopted protocols, such as smb or
|
|
sftp, so that there is no need for a server component. It is a user-level
|
|
program which means you don’t need to be a superuser or administrator.</p></div>
|
|
<div class="paragraph"><p>Together with a Pluggable Authentication Module (PAM), the intent is to provide
|
|
Roaming Home Directories for Linux (see <a href="#X80">The PAM Module</a>).</p></div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_introduction">1. Introduction</h2>
|
|
<div class="sectionbody">
|
|
<div class="paragraph"><p>It is often the case that we have multiple copies (called replicas) of a
|
|
filesystem or part of a filesystem (for example on a notebook and desktop
|
|
computer). Changes to each replica are often made independently, and as a
|
|
result, they do not contain the same information. In that case, a file
|
|
synchronizer is used to make them consistent again, without losing any
|
|
information.</p></div>
|
|
<div class="paragraph"><p>The goal is to detect conflicting updates (files which have been modified) and
|
|
propagate non-conflicting updates to each replica. If there are no conflicts
|
|
left, we are done, and the replicas are identical. To resolve or handle
|
|
conflicts there are several algorithms available. They will be discussed
|
|
one of the following sections.</p></div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_basics">2. Basics</h2>
|
|
<div class="sectionbody">
|
|
<div class="paragraph"><p>This section describes some basics of file synchronization.</p></div>
|
|
<div class="sect2">
|
|
<h3 id="_paths">2.1. Paths</h3>
|
|
<div class="paragraph"><p>A path normally refers to a point which contains a set of files which should be
|
|
synchronized. It is specified relative to the root of the replica locally, but
|
|
has to be absolute if you use a protocol. The path is just a sequence of names
|
|
separated by <em>/</em>.</p></div>
|
|
<div class="admonitionblock">
|
|
<table><tr>
|
|
<td class="icon">
|
|
<img src="./images/icons/note.png" alt="Note" />
|
|
</td>
|
|
<td class="content">The path separator is always a forward slash <em>/</em>, even for Windows.</td>
|
|
</tr></table>
|
|
</div>
|
|
<div class="paragraph"><p>csync always uses the absolute path on remote replicas. This could
|
|
<em>sftp://gladiac:secret@myserver/home/gladiac</em> for sftp.</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_what_is_an_update">2.2. What is an update?</h3>
|
|
<div class="paragraph"><p>The contents of a path could be a file, a directory or a symbolic link
|
|
(symbolic links are not supported yet). To be more precise, if the path refers
|
|
to:</p></div>
|
|
<div class="ulist"><ul>
|
|
<li>
|
|
<p>
|
|
a regular file: the contents of the file are the byte stream and the
|
|
metadata of the file.
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
a directory: then the content is the metadata of the directory.
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
a symbolic link: the content is the named file the link points to.
|
|
</p>
|
|
</li>
|
|
</ul></div>
|
|
<div class="paragraph"><p>csync keeps a record of each path which has been successfully synchronized. The
|
|
path gets compared with the record and if it has changed since the last
|
|
synchronization, we have an update. This is done by comparing the modification
|
|
or change (modification time of the metadata) time. This is the way how updates
|
|
are detected.</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_what_is_a_conflict">2.3. What is a conflict?</h3>
|
|
<div class="paragraph"><p>A path is conflicting if it fulfills the following conditions:</p></div>
|
|
<div class="olist arabic"><ol class="arabic">
|
|
<li>
|
|
<p>
|
|
it has been updated in one replica,
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
it or any of its descendants has been updated on the other replica too, and
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
its contents in are not identical.
|
|
</p>
|
|
</li>
|
|
</ol></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_file_synchronization">3. File Synchronization</h2>
|
|
<div class="sectionbody">
|
|
<div class="paragraph"><p>The primary goal of the file synchronizer is correctness. It may change
|
|
scattered or large parts of the filesystem. Since this in mostly not monitored
|
|
by the user, and the file synchronizer is in a position to harm the system,
|
|
csync must be safe, even in the case of unexpected errors (e.g. disk full).
|
|
What was done to make csync safe is described in the following sections.</p></div>
|
|
<div class="paragraph"><p>One problem concerning correctness is the handling of conflicts. Each file
|
|
synchronizer tries to propagate conflicting changes to the other replica. At
|
|
the end both replicas should be identical. There are different strategies to
|
|
fulfill these goals.</p></div>
|
|
<div class="paragraph"><p>csync is a three-phase file synchronizer. The decision for this design was that
|
|
user interaction should be possible and it should be easy to understand the
|
|
process. The three phases are update detection, reconciliation and propagation.
|
|
These will be described in the following sections.</p></div>
|
|
<div class="sect2">
|
|
<h3 id="_update_detection">3.1. Update detection</h3>
|
|
<div class="paragraph"><p>There are different strategies for update detection. csync uses a state-based
|
|
modtime-inode update detector. This means it uses the modification time to
|
|
detect updates. It doesn’t require many resources. A record of each file is
|
|
stored in a database (called statedb) and compared with the current
|
|
modification time during update detection. If the file has changed since the
|
|
last synchronization an instruction is set to evaluate it during the
|
|
reconciliation phase. If we don’t have a record for a file we investigate, it
|
|
is marked as new.</p></div>
|
|
<div class="paragraph"><p>It can be difficult to detect renaming of files. This problem is also solved
|
|
by the record we store in the statedb. If we don’t find the file by the name
|
|
in the database, we search for the inode number. If the inode number is found
|
|
then the file has been renamed.</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_reconciliation">3.2. Reconciliation</h3>
|
|
<div class="paragraph"><p>The most important component is the update detector, because the reconciler
|
|
depends on it. The correctness of reconciler is mandatory because it can damage
|
|
a filesystem. It decides which file:</p></div>
|
|
<div class="ulist"><ul>
|
|
<li>
|
|
<p>
|
|
Stays untouched
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
Has a conflict
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
Gets synchronized
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
or is <strong>deleted</strong>
|
|
</p>
|
|
</li>
|
|
</ul></div>
|
|
<div class="paragraph"><p>A wrong decision of the reconciler leads in most cases to a loss of data. So
|
|
there are several conditions which a file synchronizer has to follow.</p></div>
|
|
<div class="sect3">
|
|
<h4 id="_algorithms">3.2.1. Algorithms</h4>
|
|
<div class="paragraph"><p>For conflict resolution several different algorithms could be implemented. The
|
|
most common algorithms are the merge and the conflict algorithm. The first
|
|
is a batch algorithm and the second is one which needs user interaction.</p></div>
|
|
<div class="sect4">
|
|
<h5 id="_merge_algorithm">Merge algorithm</h5>
|
|
<div class="paragraph"><p>The merge algorithm is an algorithm which doesn’t need any user interaction. It
|
|
is simple and used for example by Microsoft for Roaming Profiles. If it detects
|
|
a conflict (the same file changed on both replicas) then it will use the most
|
|
recent file and overwrite the other. This means you can loose some data, but
|
|
normally you want the latest file.</p></div>
|
|
</div>
|
|
<div class="sect4">
|
|
<h5 id="_conflict_algorithm">Conflict algorithm</h5>
|
|
<div class="paragraph"><p>This is not implemented yet.</p></div>
|
|
<div class="paragraph"><p>If a file has a conflict the user has to decide which file should be used.</p></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_propagation">3.3. Propagation</h3>
|
|
<div class="paragraph"><p>The next instance of the file synchronizer is the propagator. It uses the
|
|
calculated records to apply them on the current replica.</p></div>
|
|
<div class="paragraph"><p>The propagator uses a two-phase-commit mechanism to simulate an atomic
|
|
filesystem operation.</p></div>
|
|
<div class="paragraph"><p>In the first phase we copy the file to a temporary file on the opposite
|
|
replica. This has the advantage that we can check if the file which has been
|
|
copied to the opposite replica has been transfered successfully. If the
|
|
connection gets interrupted during the transfer we still have the original
|
|
states of the file. This means no data will be lost.</p></div>
|
|
<div class="paragraph"><p>In the second phase the file on the opposite replica will be overwritten by
|
|
the temporary file.</p></div>
|
|
<div class="paragraph"><p>After a successful propagation we have to merge the trees to reflect the
|
|
current state of the filesystem tree. This updated tree will be written as a
|
|
journal into the state database. It will be used during the update detection of
|
|
the next synchronization. See above for a description of the state database
|
|
during synchronization.</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_robustness">3.4. Robustness</h3>
|
|
<div class="paragraph"><p>This is a very important topic. The file synchronizer should not crash, and if
|
|
it has crashed, there should be no loss of data. To achieve this goal there are
|
|
several mechanisms which will be discussed in the following sections.</p></div>
|
|
<div class="sect3">
|
|
<h4 id="_crash_resistance">3.4.1. Crash resistance</h4>
|
|
<div class="paragraph"><p>The synchronization process can be interrupted by different events, this can
|
|
be:</p></div>
|
|
<div class="ulist"><ul>
|
|
<li>
|
|
<p>
|
|
the system could be halted due to errors.
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
the disk could be full or the quota exceeded.
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
the network or power cable could be pulled out.
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
the user could force a stop of the synchronization process.
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
various communication errors could occur.
|
|
</p>
|
|
</li>
|
|
</ul></div>
|
|
<div class="paragraph"><p>That no data will be lost due to an event we enforce the following invariant:</p></div>
|
|
<div class="admonitionblock">
|
|
<table><tr>
|
|
<td class="icon">
|
|
<img src="./images/icons/important.png" alt="Important" />
|
|
</td>
|
|
<td class="content">At every moment of the synchronization each file, has either its
|
|
original content or its correct final content.</td>
|
|
</tr></table>
|
|
</div>
|
|
<div class="paragraph"><p>This means that the original content can not be incorrect, no data can be lost
|
|
until we overwrite it after a successful synchronization. Therefore, each
|
|
interrupted synchronization process is a partial sync and can be continued and
|
|
completed by simply running csync again. The only problem could be an error of
|
|
the filesystem, so we reach this invariant only approximately.</p></div>
|
|
</div>
|
|
<div class="sect3">
|
|
<h4 id="_transfer_errors">3.4.2. Transfer errors</h4>
|
|
<div class="paragraph"><p>With the Two-Phase-Commit we check the file size after the file has transferred
|
|
and we are able to detect transfer errors. A more robust approach would be a
|
|
transfer protocol with checksums, but this is not doable at the moment. We may
|
|
add this in the future.</p></div>
|
|
<div class="paragraph"><p>Future filesystems, like btrfs, will help to compare checksums instead of the
|
|
filesize. This will make the synchronization safer. This does not imply that it
|
|
is unsafe now, but checksums are safer than simple filesize checks.</p></div>
|
|
</div>
|
|
<div class="sect3">
|
|
<h4 id="_database_loss">3.4.3. Database loss</h4>
|
|
<div class="paragraph"><p>It is possible that the state database could get corrupted. If this happens,
|
|
all files get evaluated. In this case the file synchronizer wont delete any
|
|
file, but it could occur that deleted files will be restored from the other
|
|
replica.</p></div>
|
|
<div class="paragraph"><p>To prevent a corruption or loss of the database if an error occurs or the user
|
|
forces an abort, the synchronizer is working on a copy of the database and will
|
|
use a Two-Phase-Commit to save it at the end.</p></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_getting_started">4. Getting started</h2>
|
|
<div class="sectionbody">
|
|
<div class="sect2">
|
|
<h3 id="_installing_csync">4.1. Installing csync</h3>
|
|
<div class="paragraph"><p>See the <tt>README</tt> and <tt>INSTALL</tt> files for install prerequisites and
|
|
procedures. Packagers should take a look at <a href="#X90">Appendix A: Packager Notes</a>.</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_using_the_commandline_client">4.2. Using the commandline client</h3>
|
|
<div class="paragraph"><p>The synopsis of the commandline client is</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><tt>csync [OPTION...] SOURCE DESTINATION</tt></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>It synchronizes the content of SOURCE with DESTINATION and vice versa. The
|
|
DESTINATION can be a local directory or a remote file server.</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><tt>csync /home/csync scheme://user:password@server:port/full/path</tt></pre>
|
|
</div></div>
|
|
<div class="sect3">
|
|
<h4 id="_examples">4.2.1. Examples</h4>
|
|
<div class="paragraph"><p>To synchronize two local directories:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><tt>csync /home/csync/replica1 /home/csync/relplica2</tt></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>Two synchronizer a local directory with an smb server, use</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><tt>csync /home/csync smb://rupert.galaxy.site/Users/csync</tt></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>If you use kerberos, you don’t have to specify a username or a password. If you
|
|
don’t use kerberos, the commandline client will ask about the user and the
|
|
password. If you don’t want to be prompted, you can specify it on the
|
|
commandline:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><tt>csync /home/csync smb://csync:secret@rupert.galaxy.site/Users/csync</tt></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>If you use the sftp protocol and want to specify a port, you do it the
|
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following way:</p></div>
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<div class="literalblock">
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<div class="content">
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<pre><tt>csync /home/csync sftp://csync@krikkit.galaxy.site:2222/home/csync</tt></pre>
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</div></div>
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<div class="paragraph"><p>The remote destination is supported by plugins. By default csync ships with smb
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and sftp support. For more information, see the manpage of <tt>csync(1)</tt>.</p></div>
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</div>
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</div>
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<div class="sect2">
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<h3 id="_exclude_lists">4.3. Exclude lists</h3>
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<div class="paragraph"><p>csync provides exclude lists with simple shell wildcard patterns. There is a
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global exclude list, which is normally located in
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<em>/etc/csync/csync_exclude.conf</em> and it has already some sane defaults. If you
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run csync the first time, it will create an empty exclude list for the user.
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This file will be <em>~/.csync/csync_exclude.conf</em>. csync considers both
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configuration files and an additional one if you specify it.</p></div>
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<div class="paragraph"><p>The entries in the file are newline separated. Use
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<em>/etc/csync/csync_exclude.conf</em> as an example.</p></div>
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</div>
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<div class="sect2">
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<h3 id="_debug_messages_and_dry_run">4.4. Debug messages and dry run</h3>
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<div class="paragraph"><p>By default the csync client logs to stderr and you can increase the debug
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|
level with a commandline options.</p></div>
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<div class="paragraph"><p>To simulate a run of the file synchronizer, you should set the priority to
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|
<em>debug</em> for the categories <em>csync.updater</em> and <em>csync.reconciler</em> in the config
|
|
file <em>~/.csync/csync_log.conf</em>. Then run csync with the <em>--dry-run</em> option.
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This will only run update detection and reconciliation.</p></div>
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</div>
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<div class="sect2">
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<h3 id="X80">4.5. The PAM module</h3>
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<div class="paragraph"><p>pam_csync is a PAM module to provide roaming home directories for a user
|
|
session. This module is aimed at environments with central file servers where a
|
|
user wishes to store his home directory. The Authentication Module verifies the
|
|
identity of a user and triggers a synchronization with the server on the first
|
|
login and the last logout. More information can be found in the manpage of the
|
|
module pam_csync(8) or pam itself pam(8).</p></div>
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</div>
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</div>
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</div>
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<div class="sect1">
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<h2 id="X90">5. Appendix A: Packager Notes</h2>
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<div class="sectionbody">
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<div class="paragraph"><p>Read the <tt>README</tt>, <tt>INSTALL</tt> and <tt>FAQ</tt> files (in the distribution root
|
|
directory).</p></div>
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</div>
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</div>
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</div>
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<div id="footnotes"><hr /></div>
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<div id="footer">
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<div id="footer-text">
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Last updated 2012-10-29 12:05:41 CET
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</div>
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</div>
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</body>
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