Changes between Version 3 and Version 4 of TracUpgrade


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Timestamp:
Dec 4, 2020, 2:27:59 PM (3 years ago)
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trac
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  • TracUpgrade

    v3 v4  
    1 = Upgrade Instructions =
     1= Upgrade Instructions
    22[[TracGuideToc]]
    3 
    4 == Instructions ==
    5 
    6 Typically, there are seven steps involved in upgrading to a newer version of Trac:
    7 
    8 === 1. Update the Trac Code === #UpdatetheTracCode
    9 
    10 Get the new version as described in TracInstall, or your operating system specific procedure.
    11 
    12 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:
    13 
     3[[PageOutline(2-4,,inline,unnumbered)]]
     4
     5== Instructions
     6
     7There are seven recommended steps for upgrading to a newer version of Trac:
     8
     9=== 1. Check your plugins
     10
     11Check whether your plugins are compatible with the version of Trac that you are upgrading to. Obsolete plugins listed in the [#VersionSpecificSteps version specific steps] below should be uninstalled or disabled.
     12
     13If you are upgrading to a minor release, plugin compatibility is usually not a concern because the Trac API rarely changes, and major features are usually not introduced, for minor releases.
     14
     15If your plugins are installed from [https://trac-hacks.org trac-hacks.org] you can check compatibility by looking for a tag on the project page corresponding to a major release (e.g. `1.2`). If you are unsure, you'll want to contact the plugin author or ask on the [trac:MailingList MailingList].
     16
     17If you are running several Trac plugins it is good to test the upgrade and plugin functionality in a staging instance of your site before upgrading your production instance. Remember, plugin authors are responsible for Trac version compatibility and plugins can interact in unexpected ways. Your Trac instance may have a unique combination of plugins and therefore it's advised that you do some verification testing when making any changes to your site.
     18
     19=== 2. Bring your server off-line
     20
     21It 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].
     22
     23Although 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. You may also wish to create a full backup of your server.
     24
     25=== 3. Update Trac and dependencies #UpdatetheTracCode
     26
     27The packages are available through several channels, as described in [trac:TracDownload]. If your Trac instance was installed through an operating system package manager or an installer on Windows, proceed with the standard steps that are appropriate for your operating system.
     28
     29If you are managing your Trac installation using command line tools, `pip` is the preferred tool to upgrade a Trac instance because it will uninstall the old version. The following command will upgrade your Trac installation using the package published to [https://pypi.python.org/pypi/Trac PyPI].
     30
     31{{{#!sh
     32$ pip install --upgrade Trac
     33}}}
     34
     35The upgrade command will give you the latest release of Trac. If instead you wish to upgrade to a different version, such as a minor release of Trac when there is a newer major release available, then specify the Trac version in the `pip` command.
     36
     37{{{#!sh
     38$ pip install --upgrade Trac==1.2.1
     39}}}
     40
     41You should also upgrade dependencies so they are compliant with the [TracInstall#Dependencies required versions].
     42
     43=== 4. Upgrade the Trac Environment #UpgradetheTracEnvironment
     44
     45Environment upgrades are not necessary for minor version releases unless otherwise noted.
     46
     47On starting your web server after upgrading Trac, a message will be displayed for projects that need to be upgraded and the projects will not be accessible until the upgrade is run.
     48
     49The upgrade is run using a [TracAdmin trac-admin] command:
     50{{{#!sh
     51$ trac-admin /path/to/projenv upgrade
     52}}}
     53
     54This command will not have any effect if the environment is already up-to-date.
     55
     56It is recommended that you set the [[TracIni#logging-log_level-option|log_level]] to `INFO` before running the upgrade. The additional information in the logs can be helpful in case something unexpected occurs during the upgrade.
     57
     58Note that a backup of your database will be performed automatically prior to the upgrade. The backup is saved in the location specified by [[TracIni#trac-backup_dir-option|backup_dir]].
     59
     60=== 5. Update the Trac Documentation === #UpdatetheTracDocumentation
     61
     62By default, every [TracEnvironment Trac environment] includes a copy of the Trac documentation for the installed version. To keep the documentation in sync with the installed version of Trac, upgrade the documentation:
     63{{{#!sh
     64$ trac-admin /path/to/projenv wiki upgrade
     65}}}
     66
     67Note that this procedure will leave your `WikiStart`, `InterMapTxt` and `SandBox` pages unaltered. Local changes to other pages that are distributed with Trac will be overwritten, however these pages are read-only by default for Environments created in Trac 1.3.3 and later.
     68
     69=== 6. Refresh static resources
     70
     71If 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 deploy command]. The `deploy` command will extract static resources and CGI scripts (`trac.wsgi`, etc) from the new Trac version and plugins into `/deploy/path`.
     72{{{#!sh
     73$ trac-admin /path/to/env deploy /deploy/path
     74}}}
     75
     76Before refreshing, it is recommended that you remove the directory in which your static resources are deployed. The directory location depends on the choice you made during installation. This cleanup is not mandatory, but makes it easier to troubleshoot issues as your installation is uncluttered by unused assets from a previous release. As usual, make a backup before deleting the directory.
     77
     78{{{#!div style="border: 1pt dotted; margin: 1em"
     79**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 sufficient.
     80{{{#!comment
     81Remove above note once #9936 is fixed.
     82}}}
     83}}}
     84
     85=== 7. Steps specific to a given Trac version #VersionSpecificSteps
     86
     87==== Upgrading from Trac 1.2 to 1.4 #to1.4
     88
     89===== Python 2.6 no longer supported
     90
     91Upgrade Python to 2.7, but not 3.0 or greater.
     92
     93===== MySQL-python no longer supported
     94
     95[https://pypi.python.org/pypi/PyMySQL PyMySQL] is the supported MySQL database library, support for [https://pypi.python.org/pypi/MySQL-python MySQL-python] has been removed.
     96
     97===== Obsolete Plugins
     98
     99Trac has added functionality equivalent to the following plugins:
     100
     101* [https://trac-hacks.org/wiki/DynamicVariablesPlugin DynamicVariablesPlugin]: dynamic variables are autocompleted
     102* [https://trac-hacks.org/wiki/NavAddPlugin NavAddPlugin]: see TracNavigation
     103* [https://trac-hacks.org/wiki/FlexibleAssignToPlugin FlexibleAssignToPlugin]: subclass `ConfigurableTicketWorkflow` and override `get_allowed_owners`
     104* [https://trac-hacks.org/wiki/TracMigratePlugin TracMigratePlugin]: Use the `trac-admin` [TracAdmin#ChangingDatabaseBackend convert_db command]
     105
     106The plugins should be removed when upgrading Trac to 1.4.
     107
     108===== Jinja2 is the new template engine
     109
     110Content is now generated by using the Jinja2 template
     111engine. You may want to verify that your plugins are
     112compatible with this change.
     113(TODO: expand...)
     114
     115If you customized the Trac templates, or the `site.html`
     116template, you'll need to adapt that as well.
     117(TODO: expand...) See [#CustomizedTemplates]
     118
     119===== New permission policies for Wiki and Ticket realms
     120
     121Since 1.3.2 there are new permission policies for the ticket and wiki systems. `DefaultTicketPolicy` allows an authenticated users with `TICKET_APPEND` or `TICKET_CHPROP` to modify the description of a ticket they reported. It also implements the pre-1.3.2 behavior of allowing users to edit their own ticket comments. [#Newpermissionspolicyforread-onlywikipages ReadonlyWikiPolicy], added in 1.1.2, is renamed to `DefaultWikiPolicy`. The new permission policies can be easily replaced with alternate implementations if the default behavior is not desired.
     122
     123If `[trac] permission_policy` has the default value `ReadonlyWikiPolicy, DefaultPermissionPolicy, LegacyAttachmentPolicy`, then `DefaultWikiPolicy, DefaultTicketPolicy` should be automatically appended to the list when upgrading the environment:
     124{{{#!ini
     125[trac]
     126permission_policies = DefaultWikiPolicy,
     127 DefaultTicketPolicy,
     128 DefaultPermissionPolicy,
     129 LegacyAttachmentPolicy
     130}}}
     131
     132If other permission policies are enabled, `trac.ini` will need to be edited to add `DefaultWikiPolicy, DefaultTicketPolicy` to `permission_policies`. See [wiki:TracFineGrainedPermissions#DefaultWikiPolicyandDefaultTicketPolicy] for additional details on the proper ordering.
     133
     134===== Description field added to ticket enums #enum-description-field
     135
     136The ticket enums now have a //description// field. An //ambiguous column name// error may be seen for reports that reference the `description` column of another table and join the `enum` table with that table (e.g. `ticket`, `component`). The reports {1}, {2}, {3}, {4}, {5}, {7}, and {8} are modified by an upgrade step to fix the issue, but the modification may not succeed if the default reports have been modified, in which case `upgrade` will output a message to the terminal instructing the user to modify the reports. User-created reports may also need to be modified.
     137
     138Reports that display the error need to be modified to prefix the `description` column with the appropriate table name or alias. For example, if the `ticket` table is aliased as `t` (`ticket t` or `ticket AS t`), replace `description` with `t.description` if the report should use the ticket's `description` column.
     139
     140===== Removed `<repostype>` and `<repospath>` arguments from TracAdmin `initenv` command
     141
     142The TracAdmin `initenv` command allowed the default repository to be specified using the third and fourth positional arguments of `initenv`:
    14143{{{
    15 # easy_install --upgrade Trac==0.12
    16 }}}
    17 
    18 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]).
    19 
    20 You 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.
    21 The location of the site-packages directory depends on the operating system and the location in which Python was installed. However, the following locations are typical:
    22  * on Linux: `/usr/lib/python2.X/site-packages`
    23  * on Windows: `C:\Python2.X\lib\site-packages`
    24  * on MacOSX: `/Library/Python/2.X/site-packages`
    25 
    26 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.)
    27 
    28 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.
    29 
    30 === 2. Upgrade the Trac Environment === #UpgradetheTracEnvironment
    31 
    32 Environment upgrades are not necessary for minor version releases unless otherwise noted.
    33 
    34 After 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]:
    35 {{{
    36 trac-admin /path/to/projenv upgrade
    37 }}}
    38 
    39 This command will do nothing if the environment is already up-to-date.
    40 
    41 Note that a backup of your database will be performed automatically prior to the upgrade.
    42 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:
    43 {{{
    44 trac-admin /path/to/projenv upgrade --no-backup
    45 }}}
    46 
    47 === 3. Update the Trac Documentation === #UpdatetheTracDocumentation
    48 
    49 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:
    50 {{{
    51 trac-admin /path/to/projenv wiki upgrade
    52 }}}
    53 
    54 Note that this procedure will leave your `WikiStart` page intact.
    55 
    56 === 4. Resynchronize the Trac Environment Against the Source Code Repository ===
    57 
    58 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:
    59 
    60 {{{
    61 trac-admin /path/to/projenv repository resync '*'
    62 }}}
    63 
    64 === 5. Refresh static resources ===
    65 
    66 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:
    67 {{{
    68 trac-admin /path/to/env deploy /deploy/path
    69 }}}
    70 this will extract static resources and CGI scripts (`trac.wsgi`, etc) from new Trac version and its plugins into `/deploy/path`.
    71 
    72 Some web browsers cache CSS and Javascript files persistently, so you may need to instruct your users to manually erase the contents of their browser's cache.
    73 
    74 === 6. Steps specific to a given Trac version  ===
    75 ==== Upgrading from Trac 0.11 to Trac 0.12 ====
    76 ===== Python 2.3 no longer supported =====
    77 The minimum supported version of python is now 2.4
    78 
    79 ===== SQLite v3.x required =====
    80 SQLite 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.
    81 
    82 ===== PySqlite 2 required =====
    83 PySqlite 1.1.x is no longer supported. Please install 2.5.5 or later if possible (see [#Tracdatabaseupgrade Trac database upgrade] below).
    84 
    85 ===== Multiple Repository Support =====
    86 The latest version includes support for multiple repositories. If you plan to add more repositories to your Trac instance, please refer to TracRepositoryAdmin#Migration.
    87 
    88 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.
    89 
    90 ===== Improved repository synchronization =====
    91 In addition to supporting multiple repositories, there is now a more efficient method for synchronizing Trac and your repositories.
    92 
    93 While you can keep the same synchronization as in 0.11 adding the post-commit hook as outlined in TracRepositoryAdmin#Synchronization and TracRepositoryAdmin#ExplicitSync will allow more efficient synchronization and is more or less required for multiple repositories.
    94 
    95 Note 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, 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.
    96 
    97 ===== Authz permission checking =====
    98 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).
    99 
    100 ===== Microsecond timestamps =====
    101 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.
    102 
    103 ==== Upgrading from Trac 0.10 to Trac 0.11 ====
    104 ===== Site Templates and Styles =====
    105 The templating engine has changed in 0.11 to Genshi, please look at TracInterfaceCustomization for more information.
    106 
    107 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.
    108 
    109 ===== Trac Macros, Plugins =====
    110 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.
    111 
    112 ===== For FCGI/WSGI/CGI users =====
    113 For those who run Trac under the CGI environment, run this command in order to obtain the trac.*gi file:
    114 {{{
    115 trac-admin /path/to/env deploy /deploy/directory/path
    116 }}}
    117 
    118 This 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.
    119 
    120 ===== Web Admin plugin integrated =====
    121 If you had the webadmin plugin installed, you can uninstall it as it is part of the Trac code base since 0.11.
    122 
    123 === 7. Restart the Web Server === #RestarttheWebServer
    124 
    125 If you are not running [wiki:TracCgi CGI], reload the new Trac code by restarting your web server.
    126 
    127 == Known Issues ==
    128 
    129 === parent dir ===
    130 If you use a trac parent env configuration and one of the plugins in one child does not work, none of the children work.
    131 
    132 === Wiki Upgrade ===
     144initenv [<projectname> <db> [<repostype> <repospath>]]
     145}}}
     146
     147The arguments were an artifact of Trac < 0.12, which only supported a single repository. Trac 0.12 and later supports multiple repositories, which can be specified at the time of environment creation using the `--inherit` and `--config` arguments. See the [TracEnvironment#SourceCodeRepository initenv documentation] for details on specifying source code repositories.
     148
     149==== Upgrading from Trac 1.0 to 1.2 #to1.2
     150
     151===== Python 2.5 no longer supported
     152
     153Upgrade Python to at least 2.6 or 2.7, but not 3.0 or greater.
     154
     155===== Obsolete Plugins
     156
     157Trac has added functionality equivalent to the following plugins:
     158* [https://trac-hacks.org/wiki/AdminEnumListPlugin AdminEnumListPlugin]
     159* [https://trac-hacks.org/wiki/AttachmentNotifyPlugin AttachmentNotifyPlugin]: attachment notifications are sent in Trac 1.0.3 and later
     160* [https://trac-hacks.org/wiki/DateFieldPlugin DateFieldPlugin]: see the **time** [TracTicketsCustomFields#AvailableFieldTypesandOptions custom field type]
     161* [https://trac-hacks.org/wiki/FlexibleReporterNotificationPlugin FlexibleReporterNotificationPlugin]: [trac:CookBook/Notification/Subscriptions custom subscribers] can be implemented in the new extensible notification system
     162* [https://trac-hacks.org/wiki/GroupBasedRedirectionPlugin GroupBasedRedirectionPlugin]: the default handler can set as a user preference
     163* [https://trac-hacks.org/wiki/GroupingAssignToPlugin GroupingAssignToPlugin]: groups and permissions can be used in the [TracWorkflow#BasicTicketWorkflowCustomization set_owner] workflow attribute
     164* [https://trac-hacks.org/wiki/LinenoMacro LinenoMacro]: see WikiProcessors#AvailableProcessors
     165* [https://trac-hacks.org/wiki/NeverNotifyUpdaterPlugin NeverNotifyUpdaterPlugin]: see [TracNotification#notification-subscriber-section notification subscribers]
     166* [https://trac-hacks.org/wiki/QueryUiAssistPlugin QueryUiAssistPlugin]: see TracQuery#Filters.
     167* [https://trac-hacks.org/wiki/TicketCreationStatusPlugin TicketCreationStatusPlugin]: see [#NewWorkflowActions]
     168
     169The plugins should be removed when upgrading Trac to 1.2.
     170
     171===== New workflow actions #NewWorkflowActions
     172
     173The ticket creation step is controlled with a 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.
     174
     175===== New permissions policy for read-only wiki pages
     176
     177Since 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:
     178{{{#!ini
     179[trac]
     180permission_policies = ReadonlyWikiPolicy,
     181 DefaultPermissionPolicy,
     182 LegacyAttachmentPolicy
     183}}}
     184
     185If 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.
     186
     187==== Upgrading from Trac 0.12 to Trac 1.0 #to1.0
     188
     189===== Python 2.4 no longer supported
     190
     191Upgrade Python to at least 2.5, but not 3.0.
     192
     193===== Obsolete Plugins
     194
     195Trac has added functionality equivalent to the following plugins:
     196
     197* [https://trac-hacks.org/wiki/AnchorMacro AnchorMacro]
     198* [https://trac-hacks.org/wiki/BatchModifyPlugin BatchModifyPlugin]
     199* [https://trac-hacks.org/wiki/GitPlugin GitPlugin]
     200* [https://trac-hacks.org/wiki/OverrideEditPlugin OverrideEditPlugin]
     201* [https://trac-hacks.org/wiki/ProgressMeterMacro ProgressMeterMacro]
     202
     203The plugins should be removed when upgrading Trac to 1.0.
     204
     205===== Subversion components not enabled by default for new installations
     206
     207The 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:
     208{{{#!ini
     209[components]
     210tracopt.versioncontrol.svn.* = enabled
     211}}}
     212
     213The upgrade procedure should take care of this and change the TracIni appropriately, unless you already had the svn components explicitly disabled.
     214
     215===== Attachments migrated to new location #AttachmentsMigrated
     216
     217Another step in the automatic upgrade will change the way the attachments are stored. There have been reports that the attachment migration [#AttachmentsNotMigrated sometimes fails], so it's extra important that you [TracBackup backup your environment].
     218
     219In case the `attachments` directory contains some files which are //not// attachments, the last step of the migration to the new layout will not be completed: 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.
     220
     221===== Behavior of `[ticket] default_owner` changed
     222
     223Prior 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.
     224
     225==== Upgrading from older versions of Trac #OlderVersions
     226
     227For upgrades from versions older than Trac 0.12, refer first to [trac:wiki:0.12/TracUpgrade#SpecificVersions TracUpgrade for 0.12].
     228
     229For upgrades from versions older than Trac 0.10, refer first to [trac:wiki:0.10/TracUpgrade#SpecificVersions TracUpgrade for 0.10].
     230
     231== Known Issues
     232
     233=== Customized Templates
     234
     235Trac supports customization of its 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 customize the templates, be aware that you will need to repeat your changes on a copy of the new templates when you upgrade to a new release of Trac (even a minor one), as the templates will evolve. So keep a diff around.
     236
     237The preferred way to perform TracInterfaceCustomization is a custom plugin doing client-side !JavaScript transformation of the generated output, as this is more robust in case of changes: we usually won't modify an element `id` or change its CSS `class`, and if we have to do so, this will be documented in the [trac:TracDev/ApiChanges] pages.
     238
     239=== !ZipImportError
     240
     241Due 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 to anticipate and bring your server down for maintenance before upgrading.
     242See [trac:#7014] for details.
     243
     244=== Wiki Upgrade
     245
    133246`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.
    134247
    135 === Trac database upgrade ===
    136 
    137 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].
    138 
    139 == Upgrading Python ==
    140 
    141 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.
    142 
    143 === Windows and Python 2.6 ===
    144 
    145 If you've been using !CollabNet's Subversion package, you may need to uninstall that in favor of [http://alagazam.net/ Algazam], which has the Python bindings readily available (see TracSubversion).  The good news is, that works with no tweaking.
    146 
    147 == Changing Database Backend ==
    148 === SQLite to PostgreSQL ===
    149 
    150 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
    151 
    152 == Older Versions ==
    153 
    154 For upgrades from versions older than Trac 0.10, refer first to [trac:wiki:0.10/TracUpgrade#SpecificVersions].
     248=== Parent dir
     249
     250If you use a Trac parent env configuration and one of the plugins in one child does not work, none of the children will work.
     251
     252=== Attachments not migrated #AttachmentsNotMigrated
     253
     254There have been reports that attachments are not [#AttachmentsMigrated migrated] when upgrading to Trac 1.0 or later. The cause of the issue has not yet been found. If you encounter this issue, see [https://trac.edgewall.org/wiki/TracFaq#Q:Attachmentsaremissingafterupgrade the FAQ] for a workaround and please report your findings to [trac:#11370].
     255
     256== Related topics
     257
     258=== Upgrading Python
     259
     260Upgrading Python to a newer version will require reinstallation of Python packages: Trac itself of course, but also [TracInstall#Dependencies dependencies]. If you are using Subversion, you'll need to upgrade the [trac:TracSubversion Python bindings for SVN].
     261
     262
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