+Keepstore now uses "V4 signatures":https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html by default for S3 requests. If you are using Amazon S3, no action is needed; all regions support V4 signatures. If you are using a different S3-compatible service that does not support V4 signatures, add @V2Signature: true@ to your volume driver parameters to preserve the old behavior. See "configuring S3 object storage":{{site.baseurl}}/install/configure-s3-object-storage.html.
+
+h3. New permission system constraints
+
+Some constraints on the permission system have been added, in particular @role@ and @project@ group types now have distinct behavior. These constraints were already de-facto imposed by the Workbench UI, so on most installations the only effect of this migration will be to reassign @role@ groups to the system user and create a @can_manage@ permission link for the previous owner.
+
+# The @group_class@ field must be either @role@ or @project@. Invalid group_class are migrated to @role@.
+# A @role@ cannot own things. Anything owned by a role is migrated to a @can_manage@ link and reassigned to the system user.
+# Only @role@ and @user@ can have outgoing permission links. Permission links originating from projects are deleted by the migration.
+# A @role@ is always owned by the system_user. When a group is created, it creates a @can_manage@ link for the object that would have been assigned to @owner_uuid@. Migration adds @can_manage@ links and reassigns roles to the system user. This also has the effect of requiring that all @role@ groups have unique names on the system. If there is a name collision during migration, roles will be renamed to ensure they are unique.
+# A permission link can have the permission level (@name@) updated but not @head_uuid@, @tail_uuid@ or @link_class@.
+
+The @arvados-sync-groups@ tool has been updated to reflect these constraints, so it is important to use the version of @arvados-sync-groups@ that matches the API server version.
+
+Before upgrading, use the following commands to find out which groups and permissions in your database will be automatically modified or deleted during the upgrade.
+
+To determine which groups have invalid @group_class@ (these will be migrated to @role@ groups):
+
+<pre>
+arv group list --filters '[["group_class", "not in", ["project", "role"]]]'
+</pre>
+
+To list all @role@ groups, which will be reassigned to the system user (unless @owner_uuid@ is already the system user):
+
+<pre>
+arv group list --filters '[["group_class", "=", "role"]]'
+</pre>
+
+To list which @project@ groups have outgoing permission links (such links are now invalid and will be deleted by the migration):
+
+<pre>
+for uuid in $(arv link list --filters '[["link_class", "=", "permission"], ["tail_uuid", "like", "%-j7d0g-%"]]' |
+ jq -r .items[].tail_uuid | sort | uniq) ; do
+ arv group list --filters '[["group_class", "=", "project"], ["uuid", "=", "'$uuid'"]]' | jq .items
+done
+</pre>
+
+h2(#v2_0_0). v2.0.0 (2020-02-07)
+
+"Upgrading from 1.4":#v1_4_1
+
+Arvados 2.0 is a major upgrade, with many changes. Please read these upgrade notes carefully before you begin.
+
+h3. Migrating to centralized config.yml
+
+See "Migrating Configuration":config-migration.html for notes on migrating legacy per-component configuration files to the new centralized @/etc/arvados/config.yml@.
+
+To ensure a smooth transition, the per-component config files continue to be read, and take precedence over the centralized configuration. Your cluster should continue to function after upgrade but before doing the full configuration migration. However, several services (keepstore, keep-web, keepproxy) require a minimal `/etc/arvados/config.yml` to start:
+
+<pre>
+Clusters:
+ zzzzz:
+ Services:
+ Controller:
+ ExternalURL: "https://zzzzz.example.com"
+</pre>
+
+h3. Keep-balance configuration migration
+
+(feature "#14714":https://dev.arvados.org/issues/14714 ) The keep-balance service can now be configured using the centralized configuration file at @/etc/arvados/config.yml@. The following command line and configuration options have changed.
+
+You can no longer specify types of keep services to balance via the @KeepServiceTypes@ config option in the legacy config at @/etc/arvados/keep-balance/keep-balance.yml@. If you are still using the legacy config and @KeepServiceTypes@ has a value other than "disk", keep-balance will produce an error.
+
+You can no longer specify individual keep services to balance via the @config.KeepServiceList@ command line option or @KeepServiceList@ legacy config option. Instead, keep-balance will operate on all keepstore servers with @service_type:disk@ as reported by the @arv keep_service list@ command. If you are still using the legacy config, @KeepServiceList@ should be removed or keep-balance will produce an error.
+
+Please see the "config migration guide":{{site.baseurl}}/admin/config-migration.html and "keep-balance install guide":{{site.baseurl}}/install/install-keep-balance.html for more details.
+
+h3. Arv-git-httpd configuration migration
+
+(feature "#14712":https://dev.arvados.org/issues/14712 ) The arv-git-httpd package can now be configured using the centralized configuration file at @/etc/arvados/config.yml@. Configuration via individual command line arguments is no longer available. Please see "arv-git-httpd's config migration guide":{{site.baseurl}}/admin/config-migration.html#arv-git-httpd for more details.
+
+h3. Keepstore and keep-web configuration migration
+
+keepstore and keep-web no longer support configuration via (previously deprecated) command line configuration flags and environment variables.
+
+keep-web now supports the legacy @keep-web.yml@ config format (used by Arvados 1.4) and the new cluster config file format. Please check "keep-web's install guide":{{site.baseurl}}/install/install-keep-web.html for more details.
+
+keepstore now supports the legacy @keepstore.yml@ config format (used by Arvados 1.4) and the new cluster config file format. Please check the "keepstore config migration notes":{{site.baseurl}}/admin/config-migration.html#keepstore and "keepstore install guide":{{site.baseurl}}/install/install-keepstore.html for more details.