[[breaking-changes-5.5]]
== Breaking changes in 5.5

[[breaking_55_plugins]]
[float]
=== Ignoring hidden folders

Previous versions of Elasticsearch would skip hidden files and directories when
scanning the plugins folder. This allows broken plugin installs to remain
undetected so this leniency has been removed.

[[breaking_55_packaging_changes]]
[float]
=== Skip setting kernel parameters

Elasticsearch attempts to set the kernel parameter `vm.max_map_count` during
installation. In some environments this can fail. Previous versions of
Elasticsearch accepted a flag `ES_SKIP_SET_KERNEL_PARAMTERS` to skip this
writing. Starting in Elasticsearch 5.5.0, this flag has been removed and
instead the same functionality can be achieved by masking the `systemd-sysctl`
service.

[[breaking-changes-5.5]]
== Breaking changes in 5.5

[[breaking_55_plugins]]
[float]
=== Ignoring hidden folders

Previous versions of Elasticsearch would skip hidden files and directories when
scanning the plugins folder. This allows broken plugin installs to remain
undetected so this leniency has been removed.

[[breaking_55_packaging_changes]]
[float]
=== Skip setting kernel parameters

Elasticsearch attempts to set the kernel parameter `vm.max_map_count` during
installation. In some environments this can fail. Previous versions of
Elasticsearch accepted a flag `ES_SKIP_SET_KERNEL_PARAMTERS` to skip this
writing. Starting in Elasticsearch 5.5.0, this flag has been removed and
instead the same functionality can be achieved by masking the `systemd-sysctl`
service.

[[breaking_55_rest_changes]]
[float]
=== 404s on get alias and get mapping APIs

Previous versions of Elasticsearch did not return a 404 in all cases when a
requested alias or a requested type did not exist on the get alias or get
mapping APIs, respectively. Starting in Elasticsearch 5.5.0, these APIs
consistently return a 404 in any case when an alias or type is requested that
does not exist.

Add migration note on get alias and get mapping APIs
Add migration note on get alias and get mapping APIs

These APIs now return 404 if  any requested alias or type, respectively,
does not exist. This commit adds  a note to the migration docs regarding
this change.
