Changes between Version 1 and Version 2 of TracUpgrade


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Timestamp:
07/10/20 13:09:46 (2 years ago)
Author:
trac
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  • TracUpgrade

    v1 v2  
    1 = Upgrade Instructions =
     1= Upgrade Instructions
    22[[TracGuideToc]]
    3 
    4 A Trac environment sometimes needs to be upgraded before it can be used with a new version of Trac. This document describes the steps necessary to upgrade an environment.
    5 
    6  '''Note''': ''Environment upgrades are not necessary for minor version releases unless otherwise noted. For example, there's no need to upgrade a Trac environment created with (or upgraded) 0.8.0 when installing 0.8.4 (or any other 0.8.x release).''
    7 
    8 == General Instructions ==
    9 
    10 Typically, there are four steps involved in upgrading to a newer version of Trac:
    11 
    12 === Update the Trac Code ===
    13 
    14 Get the new version of Trac, either by downloading an offical release package or by checking it out from the [http://projects.edgewall.com/trac/wiki/SubversionRepository Subversion repository].
    15 
    16 If you're doing a major version upgrade (such as from 0.8 to 0.9), it is ''highly'' recommended that you first remove the existing Trac code. To do this, you need to delete the `trac` directory from the Python `lib/site-packages` directory. 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).
    17 
    18 If you have a source distribution, you need to run
    19 {{{
    20 python setup.py install
    21 }}}
    22 
    23 to install the new version. If you've downloaded the Windows installer, you execute it, and so on.
    24 
    25 === Upgrade the Trac Environment ===
    26 
    27 Unless noted otherwise, upgrading between major versions (such as 0.8 and 0.9) involves changes to the database schema, and possibly the layout of the [wiki:TracEnvironment environment directory]. Fortunately, Trac provides automated upgrade scripts to ease the pain. These scripts are run via [wiki:TracAdmin trac-admin]:
    28 {{{
    29 trac-admin /path/to/projenv upgrade
    30 }}}
    31 
    32 This command will do nothing if the environment is already up-to-date.
    33 
    34 Note that if you are using a PostgreSQL database, this command will fail with the message that the environment can only be backed up when you use an SQLite database. This means that you will have to backup the repository and the database manually. Then, to perform the actual upgrade, run:
    35 {{{
    36 trac-admin /path/to/projenv upgrade --no-backup
    37 }}}
    38 
    39 === Update the Trac Documentation ===
    40 
    41 Every [wiki: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, [wiki:TracAdmin trac-admin] provides a command to upgrade the documentation:
    42 {{{
    43 trac-admin /path/to/projenv wiki upgrade
    44 }}}
    45 
    46 Note that this procedure will of course leave your `WikiStart` page intact.
    47 
    48 === Restart the Web Server ===
    49 
    50 In order to reload the new Trac code you will need to restart your web server (note this is not necessary for [wiki:TracCgi CGI]).
    51 
    52 == Specific Versions ==
    53 
    54 The following sections discuss any extra actions that may need to be taken to upgrade to specific versions of Trac.
    55 
    56 == From 0.9.x to 0.10.x ==
    57 
    58 Due to some changes in the Wiki syntax, you may notice that certain parts of your pages no longer work as expected:
    59  * Previously, links to images would result in that image being embedded into the page. Since 0.10, links to images remain plain links. If you want to embed an image in the page, use the `[[Image]]` macro.
    60  * You can no longer use `%20` in wiki links to encode spaces. Instead, you should quote the name containing spaces (for example, use `wiki:"My page"` instead of `wiki:My%20page`.)
    61 
    62 Several enhancements have been made to the version control subsystem, in particular for the support of scoped repositories has been improved.
    63 It is recommended that you perform a [TracAdmin#InteractiveMode trac-admin] '''`resync`''' operation to take advantage of these improvements.
    64 
    65 Also note that the argument list of the [TracAdmin trac-admin] '''`initenv`''' command has changed: there's a new argument for determining the type of version control system. The old usage was:
    66 {{{
    67    initenv <projectname> <db> <repospath> <templatepath>
    68 }}}
    69 The new usage is:
    70 {{{
    71    initenv <projectname> <db> <repostype> <repospath> <templatepath>
    72 }}}
    73 If you're using any scripts that automate the creation of Trac environments, you will need to update them. If you're using Subversion, specify `svn` for the `<repostype>` argument.
    74 
    75 == From 0.9.3 to 0.9.4 ==
    76 
    77 There is a bug in Pysqlite 1.x that causes reports using the "%" character for `LIKE` clauses or date formatting to fail.  You will need to use escape the percent characters with another: "%%".
    78 
    79 == From 0.9.x to 0.9.3 or later ==
    80 
    81 If you are using plugins you might need to upgrade them. See http://projects.edgewall.com/trac/milestone/0.9.3 for further details.
    82 
    83 == From 0.9-beta to 0.9 ==
    84 
    85 If inclusion of the static resources (style sheets, javascript, images) is not working, check the value of the `htdocs_location` in trac.ini. For [wiki:TracModPython mod_python], [wiki:TracStandalone Tracd] and [wiki:TracFastCgi FastCGI], you can simply remove the option altogether. For [wiki:TracCgi CGI], you should fix it to point to the URL you mapped the Trac `htdocs` directory to (although you can also remove it and then [wiki:TracCgi#MappingStaticResources map the static resources]). If you're still having problems after removing the option, check the paths in the `trac/siteconfig.py` file and fix them if they're incorrect.
    86 
    87 If you've been using plugins with a beta release of Trac 0.9, or have disabled some of the built-in components, you might have to update the rules for disabling/enabling components in [wiki:TracIni trac.ini]. In particular, globally installed plugins now need to be enabled explicitly. See TracPlugins and TracIni for more information.
    88 
    89 If you want to enable the display of all ticket changes in the timeline (the “Ticket Details” option), you now have to explicitly enable that in [wiki:TracIni trac.ini], too:
    90 
    91 {{{
    92 [timeline]
    93 ticket_show_details = true
    94 }}}
    95 
    96 == From 0.8.x to 0.9 ==
    97 
    98 [wiki:TracModPython mod_python] users will also need to change the name of the mod_python handler in the Apache HTTPD configuration:
    99 {{{
    100    from: PythonHandler trac.ModPythonHandler
    101    to:   PythonHandler trac.web.modpython_frontend
    102 }}}
    103 
    104 If you have [http://initd.org/tracker/pysqlite PySQLite] 2.x installed, Trac will now try to open your SQLite database using the SQLite 3.x file format. The database formats used by SQLite 2.8.x and SQLite 3.x are incompatible. If you get an error like ''“file is encrypted or is not a database”'' after upgrading, then you must convert your database file.
    105 
    106 To do this, you need to have both SQLite 2.8.x and SQLite 3.x installed (they have different filenames so can coexist on the same system). Then use the following commands:
    107 {{{
    108  $ mv trac.db trac2.db
    109  $ sqlite trac2.db .dump | sqlite3 trac.db
    110 }}}
    111 
    112 To update multiple database files at once on linux you may use the following command (replace {{{/var/trac}}} withe the location where your trac installtions reside):
    113 {{{
    114  $ find /var/trac/ -iname "trac.db" | xargs -i bash -c "mv {} {}.2; sqlite {}.2 .dump | sqlite3 {};"
    115 }}}
    116 
    117 Remember the give the webserver write permission to trac.db.
    118 
    119 After testing that the conversion was successful, the `trac2.db` file can be deleted. For more information on the SQLite upgrade see http://www.sqlite.org/version3.html.
    120 
    121 == From 0.7.x to 0.8 ==
    122 
    123 0.8 adds a new roadmap feature which requires additional permissions. While a
    124 fresh installation will by default grant ROADMAP_VIEW and MILESTONE_VIEW
    125 permissions to anonymous, these permissions have to be granted manually when
    126 upgrading:
    127 {{{
    128  $ trac-admin /path/to/projectenv permission add anonymous MILESTONE_VIEW
    129  $ trac-admin /path/to/projectenv permission add anonymous ROADMAP_VIEW
    130 }}}
     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 is normally unchanged.
     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. `1.4`). 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, proceed with the standard steps that are appropriate for your operating system package manager. If it was installed through a Windows installer, uninstall the old Trac package before installing new Trac package.
     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==1.4.1
     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 should verify that your plugins are
     112compatible with this change.
     113
     114If you customized the Trac templates, or the `site.html`
     115template, you'll need to adapt that as well.
     116(TODO: expand...) See [#CustomizedTemplates]. Email [TracNotification#CustomizingContent notification templates] also need to
     117be adapted.
     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 user 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 `trac-admin` `initenv` command
     141
     142The TracAdmin `initenv` command allowed the default repository to be specified using the third and fourth positional arguments of `initenv`:
     143{{{#!sh
     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===== Navigation Ordering Moved
     188
     189The mainnav and metanav configuration ordering have
     190been moved from `[trac]` `mainnav` and `[trac]` `metanav` to the `[mainnav]` and `[metanav]` sections. The ordering is now specified using the `order` attribute as described in [TracNavigation#nav-order TracNavigation].
     191
     192The new configuration values will be written to trac.ini on upgrade, preserving the navigation order for the environment. You may need to edit trac.ini
     193if you use a shared [TracIni#GlobalConfiguration global configuration].
     194For example, if you wish to specify the navigation ordering for several environments in `global.ini`, you'll
     195need to add the `[mainnav]` and `[metanav]` sections
     196in that file and delete those sections from each
     197environment's trac.ini.
     198
     199==== Upgrading from Trac 0.12 to Trac 1.0 #to1.0
     200
     201===== Python 2.4 no longer supported
     202
     203Upgrade Python to at least 2.5, but not 3.0.
     204
     205===== Obsolete Plugins
     206
     207Trac has added functionality equivalent to the following plugins:
     208
     209* [https://trac-hacks.org/wiki/AnchorMacro AnchorMacro]
     210* [https://trac-hacks.org/wiki/BatchModifyPlugin BatchModifyPlugin]
     211* [https://trac-hacks.org/wiki/GitPlugin GitPlugin]
     212* [https://trac-hacks.org/wiki/OverrideEditPlugin OverrideEditPlugin]
     213* [https://trac-hacks.org/wiki/ProgressMeterMacro ProgressMeterMacro]
     214
     215The plugins should be removed when upgrading Trac to 1.0.
     216
     217===== Subversion components not enabled by default for new installations
     218
     219The 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:
     220{{{#!ini
     221[components]
     222tracopt.versioncontrol.svn.* = enabled
     223}}}
     224
     225The upgrade procedure should take care of this and change the TracIni appropriately, unless you already had the svn components explicitly disabled.
     226
     227===== Attachments migrated to new location #AttachmentsMigrated
     228
     229Another 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].
     230
     231In 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.
     232
     233===== Behavior of `[ticket] default_owner` changed
     234
     235Prior 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.
     236
     237==== Upgrading from older versions of Trac #OlderVersions
     238
     239For upgrades from versions older than Trac 0.12, refer first to [trac:wiki:0.12/TracUpgrade#SpecificVersions TracUpgrade for 0.12].
     240
     241For upgrades from versions older than Trac 0.10, refer first to [trac:wiki:0.10/TracUpgrade#SpecificVersions TracUpgrade for 0.10].
     242
     243== Known Issues
     244
     245=== Customized Templates
     246
     247Trac 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.
     248
     249The 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.
     250
     251=== !ZipImportError
     252
     253Due 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.
     254See [trac:#7014] for details.
     255
     256=== Wiki Upgrade
     257
     258`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.
     259
     260=== Parent dir
     261
     262If you use a Trac parent env configuration and one of the plugins in one child does not work, none of the children will work.
     263
     264=== Attachments not migrated #AttachmentsNotMigrated
     265
     266There 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].
     267
     268== Related topics
     269
     270=== Upgrading Python
     271
     272Upgrading 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].
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     274
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