Changes between Version 5 and Version 6 of TracUpgrade


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Timestamp:
Sep 17, 2017, 10:22:15 PM (7 years ago)
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trac
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  • TracUpgrade

    v5 v6  
    1 = Upgrade Instructions =
     1= Upgrade Instructions
    22[[TracGuideToc]]
    33[[PageOutline(2-4,,inline,unnumbered)]]
    44
    5 == Instructions ==
     5== Instructions
    66
    77Typically, there are seven steps involved in upgrading to a newer version of Trac:
    … …  
    99=== 1. Bring your server off-line
    1010
    11 It is not a good idea to update a running server: the server processes may have parts of the current packages cached in memory, and updating the code will likely trigger [#ZipImportError internal errors]. 
    12 
    13 === 2. Update the Trac Code === #UpdatetheTracCode
    14 
    15 Get the new version as described in TracInstall, or your operating system specific procedure.
    16 
    17 If you already have a 0.11 version of Trac installed via `easy_install`, it might be easiest to also use `easy_install` to upgrade your Trac installation:
    18 
    19 {{{
    20 # easy_install --upgrade Trac==0.12
    21 }}}
    22 
    23 If you do a manual (not operating system-specific) upgrade, you should also stop any running Trac servers before the installation. Doing "hot" upgrades is not advised, especially on Windows ([trac:#7265]).
     11It is not a good idea to update a running server: the server processes may have parts of the current packages cached in memory, and updating the code will likely trigger [#ZipImportError internal errors].
     12
     13Although a database backup will be implicitly created by default when upgrading the environment, it is always a good idea to perform a full backup of the environment using the [TracBackup hotcopy] command before beginning.
     14
     15=== 2. Update the Trac Code #UpdatetheTracCode
     16
     17Get the new version as described in TracInstall, or through your operating system package manager.
     18
     19If you already an earlier version of Trac installed via `easy_install`, it might be easiest to also use `easy_install` to upgrade your Trac installation:
     20
     21{{{#!sh
     22easy_install --upgrade Trac
     23}}}
    2424
    2525You may also want to remove the pre-existing Trac code by deleting the `trac` directory from the Python `lib/site-packages` directory, or remove Trac `.egg` files from former versions.
    … …  
    2929 * on MacOSX: `/Library/Python/2.X/site-packages`
    3030
    31 You may also want to remove the Trac `cgi-bin`, `htdocs`, `templates` and `wiki-default` directories that are commonly found in a directory called `share/trac`. (The exact location depends on your platform.)
    32 
    33 This cleanup is not mandatory, but makes it easier to troubleshoot issues later on, as you won't waste your time looking at code or templates from a previous release that are not being used anymore... As usual, make a backup before actually deleting things.
    34 
    35 === 3. Upgrade the Trac Environment === #UpgradetheTracEnvironment
     31You may also want to remove the directory in which your static resources are [TracInstall#cgi-bin deployed]. The exact location depends on your platform. This cleanup is not mandatory, but makes it easier to troubleshoot issues later on, as your installation is uncluttered by code or templates from a previous release that is not used anymore. As usual, make a backup before actually removing things.
     32
     33=== 3. Upgrade the Trac Environment #UpgradetheTracEnvironment
    3634
    3735Environment upgrades are not necessary for minor version releases unless otherwise noted.
    3836
    3937After restarting, Trac should show the instances which need a manual upgrade via the automated upgrade scripts to ease the pain. These scripts are run via [TracAdmin trac-admin]:
    40 {{{
     38{{{#!sh
    4139trac-admin /path/to/projenv upgrade
    4240}}}
    4341
    44 This command will do nothing if the environment is already up-to-date.
    45 
    46 Note that a backup of your database will be performed automatically prior to the upgrade.
    47 This feature is relatively new for the PostgreSQL or MySQL database backends, so if it fails, you will have to backup the database manually. Then, to perform the actual upgrade, run:
    48 {{{
    49 trac-admin /path/to/projenv upgrade --no-backup
    50 }}}
     42This command will not have any effect if the environment is already up-to-date.
     43
     44Note that a backup of your database will be performed automatically prior to the upgrade. The backup will be saved in the location specified by `[trac]` `backup_dir`.
    5145
    5246=== 4. Update the Trac Documentation === #UpdatetheTracDocumentation
    5347
    54 Every [TracEnvironment Trac environment] includes a copy of the Trac documentation for the installed version. As you probably want to keep the included documentation in sync with the installed version of Trac, [TracAdmin trac-admin] provides a command to upgrade the documentation:
    55 {{{
     48By default, every [TracEnvironment Trac environment] includes a copy of the Trac documentation for the installed version. However, to keep the included documentation in sync with the installed version of Trac, use the following [TracAdmin trac-admin] command to upgrade the documentation:
     49{{{#!sh
    5650trac-admin /path/to/projenv wiki upgrade
    5751}}}
    … …  
    5953Note that this procedure will leave your `WikiStart` page intact.
    6054
    61 
    62 === 5. Refresh static resources ===
    63 
    64 If you have set up a web server to give out static resources directly (accessed using the `/chrome/` URL) then you will need to refresh them using the same command:
    65 {{{
     55=== 5. Refresh static resources
     56
     57If you have configured your web server to serve static resources directly (accessed using the `/chrome/` URL) then you will need to refresh them using the [TracInstall#MappingStaticResources same command]:
     58{{{#!sh
    6659trac-admin /path/to/env deploy /deploy/path
    6760}}}
    68 this will extract static resources and CGI scripts (`trac.wsgi`, etc) from new Trac version and its plugins into `/deploy/path`.
    69 
    70 Some web browsers (IE, Opera) cache CSS and Javascript files aggressively, so you may need to instruct your users to manually erase the contents of their browser's cache, a forced refreshed (`<F5>`) should be enough.
     61
     62This will extract static resources and CGI scripts (`trac.wsgi`, etc) from the new Trac version and plugins into `/deploy/path`.
     63
     64{{{#!div style="border: 1pt dotted; margin: 1em"
     65**Note:** Some web browsers (IE, Opera) cache CSS and Javascript files, so you should instruct your users to manually erase the contents of their browser's cache. A forced refreshed (SHIFT + <F5>) should be enough.
    7166{{{#!comment
    7267Remove above note once #9936 is fixed.
    7368}}}
    74 
    75 === 6. Steps specific to a given Trac version  ===
    76 ==== Upgrading from Trac 0.12 to Trac 1.0 ==== #to1.0
     69}}}
     70
     71=== 6. Steps specific to a given Trac version
     72
     73==== Upgrading from Trac 1.0 to 1.2 #to1.2
     74
     75===== Python 2.5 no longer supported
     76
     77Upgrade Python to at least 2.6 or 2.7, but not 3.0 or greater.
     78
     79===== Obsolete Plugins
     80
     81Trac has added functionality equivalent to the following plugins:
     82* [https://trac-hacks.org/wiki/AdminEnumListPlugin AdminEnumListPlugin]
     83* [https://trac-hacks.org/wiki/DateFieldPlugin DateFieldPlugin]: see the **time** [TracTicketsCustomFields#AvailableFieldTypesandOptions custom field type]
     84* [https://trac-hacks.org/wiki/GroupBasedRedirectionPlugin GroupBasedRedirectionPlugin]: the default handler can set as a user preference.
     85* [https://trac-hacks.org/wiki/LinenoMacro LinenoMacro]: see WikiProcessors#AvailableProcessors
     86* [https://trac-hacks.org/wiki/NeverNotifyUpdaterPlugin NeverNotifyUpdaterPlugin]: see [TracNotification#notification-subscriber-section notification subscribers]
     87* [https://trac-hacks.org/wiki/QueryUiAssistPlugin QueryUiAssistPlugin]: see TracQuery#Filters.
     88* [https://trac-hacks.org/wiki/TicketCreationStatusPlugin TicketCreationStatusPlugin]: see [#NewWorkflowActions]
     89
     90The plugins should be removed when upgrading Trac to 1.2.
     91
     92===== New workflow actions #NewWorkflowActions
     93
     94The ticket creation step is controlled with a [TracWorkflow#TicketCreateAction workflow action]. The default workflow has `create` and `create_and_assign` actions. The `create` action will always be added when upgrading the database. The `create_and_assign` action will be added if the workflow has an //assigned// state. You may want to edit your workflow after upgrading the database to customize the actions available on the //New Ticket// page.
     95
     96===== New permissions policy for read-only wiki pages
     97
     98Since 1.1.2 the read-only attribute of wiki pages is enabled and enforced only when `ReadonlyWikiPolicy` is in the list of active permission policies. If `[trac] permission_policy` has the default value `DefaultPermissionPolicy, LegacyAttachmentPolicy`, then `ReadonlyWikiPolicy` should be automatically appended to the list when upgrading the environment:
     99{{{#!ini
     100[trac]
     101permission_policies = ReadonlyWikiPolicy,
     102 DefaultPermissionPolicy,
     103 LegacyAttachmentPolicy
     104}}}
     105
     106If other permission policies are enabled, `trac.ini` will need to have `ReadonlyWikiPolicy` appended to the list of active `permission_policies`. See TracFineGrainedPermissions#ReadonlyWikiPolicy for additional details on the proper ordering.
     107
     108==== Upgrading from Trac 0.12 to Trac 1.0 #to1.0
     109
     110===== Python 2.4 no longer supported
     111
     112Upgrade Python to at least 2.5, but not 3.0.
     113
     114===== Obsolete Plugins
     115
     116Trac has added functionality equivalent to the following plugins:
     117
     118* [https://trac-hacks.org/wiki/BatchModifyPlugin BatchModifyPlugin]
     119* [https://trac-hacks.org/wiki/GitPlugin GitPlugin]
     120* [https://trac-hacks.org/wiki/OverrideEditPlugin OverrideEditPlugin]
     121
     122The plugins should be removed when upgrading Trac to 1.0.
     123
     124===== Subversion components not enabled by default for new installations
    77125
    78126The Trac components for Subversion support are no longer enabled by default. To enable the svn support, you need to make sure the `tracopt.versioncontrol.svn` components are enabled, for example by setting the following in the TracIni:
    79 {{{
     127{{{#!ini
    80128[components]
    81129tracopt.versioncontrol.svn.* = enabled
    82130}}}
     131
    83132The upgrade procedure should take care of this and change the TracIni appropriately, unless you already had the svn components explicitly disabled.
    84133
    85 Another step in the automatic upgrade will change the way the attachments are stored. If you're a bit paranoid, you might want to take a backup of the `attachments` directory before upgrading (but if you are, you already did a full copy of the environment, no?). In case the `attachments` directory contains some files which are //not// attachments, the last step of the migration to the new layout will fail: the deletion of the now unused `attachments` directory can't be done if there are still files and folders in it. You may ignore this error, but better go have a look to these files, move them elsewhere and remove the `attachments` directory manually to cleanup the environment. The attachments themselves are now all located in your environment below the `files/attachments` directory.
    86 
    87 
    88 ==== Upgrading from Trac 0.11 to Trac 0.12 ====
    89 
    90 ===== Python 2.3 no longer supported =====
    91 The minimum supported version of python is now 2.4
    92 
    93 ===== SQLite v3.x required =====
     134===== Attachments migrated to new location
     135
     136Another step in the automatic upgrade will change the way the attachments are stored. Create a backup of the `attachments` directory before upgrading. In case the `attachments` directory contains some files which are //not// attachments, the last step of the migration to the new layout will fail: the deletion of the now unused `attachments` directory can't be done if there are still files and folders in it. You may ignore this error, but better to move them elsewhere and remove the `attachments` directory manually. The attachments themselves are now all located in your environment below the `files/attachments` directory.
     137
     138===== Behavior of `[ticket] default_owner` changed
     139
     140Prior to 1.0, the owner field of new tickets always defaulted to `[ticket] default_owner` when the value was not empty. If the value was empty, the owner field defaulted to to the Component's owner. In 1.0 and later, the `default_owner` must be set to `< default >` to make new tickets default to the Component's owner. This change allows the `default_owner` to be set to an empty value if no default owner is desired.
     141
     142==== Upgrading from Trac 0.11 to Trac 0.12
     143
     144===== Python 2.3 no longer supported
     145
     146The minimum supported version of Python is now 2.4.
     147
     148===== SQLite v3.x required
     149
    94150SQLite v2.x is no longer supported. If you still use a Trac database of this format, you'll need to convert it to SQLite v3.x first. See [trac:PySqlite#UpgradingSQLitefrom2.xto3.x] for details.
    95151
    96 ===== PySqlite 2 required =====
    97 PySqlite 1.1.x is no longer supported. Please install 2.5.5 or later if possible (see [#Tracdatabaseupgrade Trac database upgrade] below).
    98 
    99 ===== Multiple Repository Support =====
     152===== [trac:PySqlite] 2 required
     153
     154[trac:PySqlite] 1.1.x is no longer supported. Please install 2.5.5 or later if possible, see [#Tracdatabaseupgrade Trac database upgrade] below.
     155
     156===== Obsolete Plugins
     157
     158Trac has added functionality equivalent to the following plugins:
     159
     160* [https://trac-hacks.org/wiki/AutoQueryPlugin AutoQueryPlugin]
     161* [https://trac-hacks.org/wiki/AdminConsoleProviderPatch AdminConsoleProviderPatch]
     162* [https://trac-hacks.org/wiki/AnchorMacro AnchorMacro]: see WikiFormatting#SettingAnchors
     163* [https://trac-hacks.org/wiki/TicketChangePlugin TicketChangePlugin]: see [TracPermissions#TicketSystem TICKET_EDIT_COMMENT permission]
     164* [https://trac-hacks.org/wiki/TicketDeletePlugin TicketDeletePlugin]: see `tracopt.ticket.deleter`
     165* [https://trac-hacks.org/wiki/SubversionLocationPlugin SubversionLocationPlugin]: see TracRepositoryAdmin#Repositories
     166* [https://trac-hacks.org/wiki/WikiCreoleRendererPlugin WikiCreoleRendererPlugin]: see [trac:WikiCreole]
     167* [https://trac-hacks.org/wiki/RepoRevisionSyntaxPlugin RepoRevisionSyntaxPlugin] (added in 0.12.1)
     168
     169The plugins should be removed when upgrading Trac to 0.12.
     170
     171===== Multiple Repository Support
     172
    100173The latest version includes support for multiple repositories. If you plan to add more repositories to your Trac instance, please refer to TracRepositoryAdmin#Migration.
    101174
    102 This may be of interest to users with only one repository, since there's now a way to avoid the potentially costly resync check at every request.
    103 
    104 ===== Resynchronize the Trac Environment Against the Source Code Repository =====
    105 
    106 Each [TracEnvironment Trac environment] must be resynchronized against the source code repository in order to avoid errors such as "[http://trac.edgewall.org/ticket/6120 No changeset ??? in the repository]" while browsing the source through the Trac interface:
    107 
    108 {{{
     175This may be of interest to users with only one repository, since there is now a way to avoid the potentially costly resync check at every request.
     176
     177===== Resynchronize the Trac Environment Against the Source Code Repository
     178
     179Each [TracEnvironment Trac environment] must be resynchronized against the source code repository in order to avoid errors such as "[trac:#6120 No changeset ??? in the repository]" while browsing the source through the Trac interface:
     180
     181{{{#!sh
    109182trac-admin /path/to/projenv repository resync '*'
    110183}}}
    111184
    112 ===== Improved repository synchronization =====
     185===== Improved repository synchronization
     186
    113187In addition to supporting multiple repositories, there is now a more efficient method for synchronizing Trac and your repositories.
    114188
    … …  
    117191Note that if you were using the `trac-post-commit-hook`, ''you're strongly advised to upgrade it'' to the new hook documented in the above references and [TracWorkflow#Howtocombinethetracopt.ticket.commit_updaterwiththetestingworkflow here], as the old hook will not work with anything else than the default repository and even for this case, it won't trigger the appropriate notifications.
    118192
    119 ===== Authz permission checking =====
    120 The authz permission checking has been migrated to a fine-grained permission policy. If you use authz permissions (aka `[trac] authz_file` and `authz_module_name`), you must add `AuthzSourcePolicy` in front of your permission policies in `[trac] permission_policies`. You must also remove `BROWSER_VIEW`, `CHANGESET_VIEW`, `FILE_VIEW` and `LOG_VIEW` from your global permissions (with `trac-admin $ENV permission remove` or the "Permissions" admin panel).
    121 
    122 ===== Microsecond timestamps =====
    123 All timestamps in database tables (except the `session` table) have been changed from "seconds since epoch" to "microseconds since epoch" values. This change should be transparent to most users, except for custom reports. If any of your reports use date/time columns in calculations (e.g. to pass them to `datetime()`), you must divide the values retrieved from the database by 1'000'000. Similarly, if a report provides a calculated value to be displayed as a date/time (i.e. with a column named "time", "datetime", "changetime", "date", "created" or "modified"), you must provide a microsecond timestamp, that is, multiply your previous calculation with 1'000'000.
    124 
    125 ==== Upgrading from Trac 0.10 to Trac 0.11 ====
    126 ===== Site Templates and Styles =====
     193===== Authz permission checking
     194
     195The authz permission checking has been migrated to a fine-grained permission policy. If you use authz permissions (aka `[trac] authz_file` and `authz_module_name`), you must add `AuthzSourcePolicy` in front of your permission policies in `[trac] permission_policies`. You must also remove `BROWSER_VIEW`, `CHANGESET_VIEW`, `FILE_VIEW` and `LOG_VIEW` from your global permissions with `trac-admin $ENV permission remove` or the "Permissions" admin panel.
     196
     197===== Microsecond timestamps
     198
     199All timestamps in database tables, except the `session` table, have been changed from "seconds since epoch" to "microseconds since epoch" values. This change should be transparent to most users, except for custom reports. If any of your reports use date/time columns in calculations (e.g. to pass them to `datetime()`), you must divide the values retrieved from the database by 1'000'000. Similarly, if a report provides a calculated value to be displayed as a date/time (i.e. with a column named "time", "datetime", "changetime", "date", "created" or "modified"), you must provide a microsecond timestamp, that is, multiply your previous calculation with 1'000'000.
     200
     201==== Upgrading from Trac 0.10 to Trac 0.11
     202
     203===== Site Templates and Styles
     204
    127205The templating engine has changed in 0.11 to Genshi, please look at TracInterfaceCustomization for more information.
    128206
    129 If you are using custom CSS styles or modified templates in the `templates` directory of the TracEnvironment, you will need to convert them to the Genshi way of doing things. To continue to use your style sheet, follow the instructions at TracInterfaceCustomization#SiteAppearance.
    130 
    131 ===== Trac Macros, Plugins =====
    132 The Trac macros will need to be adapted, as the old-style wiki-macros are not supported anymore (due to the drop of [trac:ClearSilver] and the HDF); they need to be converted to the new-style macros, see WikiMacros. When they are converted to the new style, they need to be placed into the plugins directory instead and not wiki-macros, which is no longer scanned for macros or plugins.
    133 
    134 ===== For FCGI/WSGI/CGI users =====
     207If you are using custom CSS or modified templates in the `templates` directory of the TracEnvironment, you will need to convert them to the Genshi way of doing things. To continue to use your style sheet, follow the instructions at TracInterfaceCustomization#SiteAppearance.
     208
     209===== Trac Macros, Plugins
     210
     211The Trac macros will need to be adapted, as the old-style wiki-macros are not supported anymore due to the drop of [trac:ClearSilver] and the HDF. They need to be converted to the new-style macros, see WikiMacros. When they are converted to the new style, they need to be placed into the plugins directory instead and not wiki-macros, which is no longer scanned for macros or plugins.
     212
     213===== For FCGI/WSGI/CGI users
     214
    135215For those who run Trac under the CGI environment, run this command in order to obtain the trac.*gi file:
    136 {{{
     216{{{#!sh
    137217trac-admin /path/to/env deploy /deploy/directory/path
    138218}}}
    … …  
    140220This will create a deploy directory with the following two subdirectories: `cgi-bin` and `htdocs`. Then update your Apache configuration file `httpd.conf` with this new `trac.cgi` location and `htdocs` location.
    141221
    142 ===== Web Admin plugin integrated =====
    143 If you had the webadmin plugin installed, you can uninstall it as it is part of the Trac code base since 0.11.
    144 
    145 === 7. Restart the Web Server === #RestarttheWebServer
     222===== Web Admin plugin integrated
     223
     224If you had the [trac:WebAdmin] plugin installed, you can uninstall it as it is part of the Trac code base since 0.11.
     225
     226===== New Default Configurable Workflow
     227
     228When you run `trac-admin <env> upgrade`, your `trac.ini` will be modified to include a `[ticket-workflow]` section. The workflow configured in this case is the original workflow, so that ticket actions will behave like they did in 0.10:
     229
     230{{{#!Workflow width=500 height=240
     231leave = * -> *
     232leave.operations = leave_status
     233leave.default = 1
     234accept = new -> assigned
     235accept.permissions = TICKET_MODIFY
     236accept.operations = set_owner_to_self
     237resolve = new,assigned,reopened -> closed
     238resolve.permissions = TICKET_MODIFY
     239resolve.operations = set_resolution
     240reassign = new,assigned,reopened -> new
     241reassign.permissions = TICKET_MODIFY
     242reassign.operations = set_owner
     243reopen = closed -> reopened
     244reopen.permissions = TICKET_CREATE
     245reopen.operations = del_resolution
     246}}}
     247
     248There are some significant caveats in this, such as accepting a ticket sets it to 'assigned' state, and assigning a ticket sets it to 'new' state. So you will probably want to migrate to "basic" workflow; [trac:source:trunk/contrib/workflow/migrate_original_to_basic.py contrib/workflow/migrate_original_to_basic.py] may be helpful. See TracWorkflow for a detailed description of the new basic workflow.
     249
     250=== 7. Restart the Web Server #RestarttheWebServer
    146251
    147252If you are not running [wiki:TracCgi CGI], reload the new Trac code by restarting your web server.
    148253
    149 == Known Issues ==
    150 
    151 Things you should pay attention to, while upgrading.
     254== Known Issues
    152255
    153256=== Customized Templates
    154257
    155 Trac supports customization of its Genshi templates by placing copies of the templates in the `<env>/templates` folder of your [TracEnvironment environment] or in a common location specified in the [[TracIni#GlobalConfiguration| [inherit] templates_dir]] configuration setting. If you choose to do so, be wary that you will need to repeat your changes manually on a copy of the new templates when you upgrade to a new release of Trac (even a minor one), as the templates will likely evolve. So keep a diff around ;-)
    156 
    157 The preferred way to perform TracInterfaceCustomization is to write a custom plugin doing an appropriate `ITemplateStreamFilter` transformation, as this is more robust in case of changes: we usually won't modify element `id`s or change CSS `class`es, and if we have to do so, this will be documented in the TracDev/ApiChanges pages.
    158 
    159 === !ZipImportError ===
    160 
    161 Due to internal caching of zipped packages,  whenever the content of the packages change on disk, the in-memory zip index will no longer match and you'll get irrecoverable !ZipImportError errors. Better anticipate and bring your server down for maintenance before upgrading.
     258Trac supports customization of its Genshi templates by placing copies of the templates in the `<env>/templates` folder of your [TracEnvironment environment] or in a common location specified in the [[TracIni#GlobalConfiguration| [inherit] templates_dir]] configuration setting. If you choose to do so, be aware that you will need to repeat your changes manually on a copy of the new templates when you upgrade to a new release of Trac (even a minor one), as the templates will likely evolve. So keep a diff around.
     259
     260The preferred way to perform TracInterfaceCustomization is to write a custom plugin doing an appropriate `ITemplateStreamFilter` transformation, as this is more robust in case of changes: we usually won't modify element `id`s or change CSS `class`es, and if we have to do so, this will be documented in the [trac:TracDev/ApiChanges] pages.
     261
     262=== !ZipImportError
     263
     264Due to internal caching of zipped packages, whenever the content of the packages change on disk, the in-memory zip index will no longer match and you'll get irrecoverable !ZipImportError errors. Better anticipate and bring your server down for maintenance before upgrading.
    162265See [trac:#7014] for details.
    163266
    164 === Wiki Upgrade ===
     267=== Wiki Upgrade
     268
    165269`trac-admin` will not delete or remove default wiki pages that were present in a previous version but are no longer in the new version.
    166270
    167 === Trac database upgrade ===
    168 
    169 A known issue in some versions of PySqlite (2.5.2-2.5.4) prevents the trac-admin upgrade script from successfully upgrading the database format. It is advised to use either a newer or older version of the sqlite python bindings to avoid this error. For more details see ticket [trac:#9434].
    170 
    171 === parent dir ===
    172 If you use a trac parent env configuration and one of the plugins in one child does not work, none of the children work.
     271=== Trac database upgrade
     272
     273A known issue in some versions of [trac:PySqlite] (2.5.2-2.5.4) prevents the trac-admin upgrade script from successfully upgrading the database format. It is advised to use either a newer or older version of the sqlite python bindings to avoid this error. For more details see ticket [trac:#9434].
     274
     275=== Parent dir
     276
     277If you use a Trac parent env configuration and one of the plugins in one child does not work, none of the children will work.
    173278
    174279== Related topics
    175280
    176 === Upgrading Python ===
    177 
    178 Upgrading Python to a newer version will require reinstallation of Python packages: Trac of course; also [http://pypi.python.org/pypi/setuptools easy_install], if you've been using that.  Assuming you're using Subversion, you'll also need to upgrade the Python bindings for svn.
    179 
    180 ==== Windows and Python 2.6 ====
    181 
    182 If you've been using !CollabNet's Subversion package, you may need to uninstall that in favor of [http://alagazam.net/ Alagazam], which has the Python bindings readily available (see TracSubversion).  The good news is, that works with no tweaking.
    183 
    184 === Changing Database Backend ===
    185 ==== SQLite to PostgreSQL ====
    186 
    187 The [http://trac-hacks.org/wiki/SqliteToPgScript sqlite2pg] script on [http://trac-hacks.org trac-hacks.org] has been written to assist in migrating a SQLite database to a PostgreSQL database
    188 
    189 === Upgrading from older versions of Trac === #OlderVersions
     281=== Upgrading Python
     282
     283Upgrading Python to a newer version will require reinstallation of Python packages: Trac itself of course, but also [http://pypi.python.org/pypi/setuptools easy_install], if you've been using that. If you are using Subversion, you'll also need to upgrade the Python bindings for svn.
     284
     285==== Windows and Python 2.6
     286
     287If you've been using !CollabNet's Subversion package, you may need to uninstall that in favor of [http://alagazam.net/ Alagazam], which has the Python bindings readily available, see [trac:TracSubversion]. That package works without tweaking.
     288
     289=== Changing Database Backend
     290
     291The [https://trac-hacks.org/wiki/TracMigratePlugin TracMigratePlugin] on [https://trac-hacks.org trac-hacks.org] has been written to assist in migrating between SQLite, MySQL and PostgreSQL databases.
     292
     293=== Upgrading from older versions of Trac #OlderVersions
    190294
    191295For upgrades from versions older than Trac 0.10, refer first to [trac:wiki:0.10/TracUpgrade#SpecificVersions].