diff --git a/.rubocop.yml b/.rubocop.yml
index 1ea0b552fcb4b1483b537f23a99611a9d8842672..0f4018326a118d360a0de55df204da225d06e306 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -50,7 +50,8 @@ Style/FrozenStringLiteralComment:
     - 'danger/**/*'
     - 'db/**/*'
     - 'ee/**/*'
-    - 'lib/**/*'
+    - 'lib/gitlab/**/*'
+    - 'lib/tasks/**/*'
     - 'qa/**/*'
     - 'rubocop/**/*'
     - 'scripts/**/*'
diff --git a/changelogs/unreleased/even-more-frozen-string-lib.yml b/changelogs/unreleased/even-more-frozen-string-lib.yml
new file mode 100644
index 0000000000000000000000000000000000000000..3f5fd7710aa2943dd9394d26ebcd32d6b034cbcd
--- /dev/null
+++ b/changelogs/unreleased/even-more-frozen-string-lib.yml
@@ -0,0 +1,5 @@
+---
+title: Enable even more frozen string in lib/**/*.rb
+merge_request:
+author: gfyoung
+type: performance
diff --git a/lib/generators/rails/post_deployment_migration/post_deployment_migration_generator.rb b/lib/generators/rails/post_deployment_migration/post_deployment_migration_generator.rb
index 91175b49c799fe9e38b4bd657623d5f54f8edc4f..15cdd25e7116e4e311dedba2d54efcbabe406b4e 100644
--- a/lib/generators/rails/post_deployment_migration/post_deployment_migration_generator.rb
+++ b/lib/generators/rails/post_deployment_migration/post_deployment_migration_generator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails/generators'
 
 module Rails
diff --git a/lib/gitaly/server.rb b/lib/gitaly/server.rb
index f95e423ef22fc3da74faaa56dab790c10c65532e..7b238623418d53e3ff1ca95308a057939d5c6b01 100644
--- a/lib/gitaly/server.rb
+++ b/lib/gitaly/server.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitaly
   class Server
     def self.all
diff --git a/lib/google_api/auth.rb b/lib/google_api/auth.rb
index 1aeaa387a499263176a9a4809d69cd148a133b96..e724e58e9caa093d2f4168b0e9634826777b5e6e 100644
--- a/lib/google_api/auth.rb
+++ b/lib/google_api/auth.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module GoogleApi
   class Auth
     attr_reader :access_token, :redirect_uri, :state
diff --git a/lib/google_api/cloud_platform/client.rb b/lib/google_api/cloud_platform/client.rb
index 77b6610286f4ff48a00856d19f84d89670b00237..e74ff6a91292eb4bc1181214ed57aec6f4842ada 100644
--- a/lib/google_api/cloud_platform/client.rb
+++ b/lib/google_api/cloud_platform/client.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'google/apis/compute_v1'
 require 'google/apis/container_v1'
 require 'google/apis/cloudbilling_v1'
diff --git a/lib/haml_lint/inline_javascript.rb b/lib/haml_lint/inline_javascript.rb
index adbed20f15217648eaa027bc9c8bff12f397cb6e..5ecd6169ecf5f634bda7945186b4846458a8b753 100644
--- a/lib/haml_lint/inline_javascript.rb
+++ b/lib/haml_lint/inline_javascript.rb
@@ -1,4 +1,7 @@
-unless Rails.env.production? # rubocop:disable Naming/FileName
+# rubocop:disable Naming/FileName
+# frozen_string_literal: true
+
+unless Rails.env.production?
   require 'haml_lint/haml_visitor'
   require 'haml_lint/linter'
   require 'haml_lint/linter_registry'
diff --git a/lib/json_web_token/rsa_token.rb b/lib/json_web_token/rsa_token.rb
index d6d6af7089c92fb3ee02283ced9102782473422a..160e1e506f14d590e613bbbbe73caeab12f707e4 100644
--- a/lib/json_web_token/rsa_token.rb
+++ b/lib/json_web_token/rsa_token.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module JSONWebToken
   class RSAToken < Token
     attr_reader :key_file
diff --git a/lib/json_web_token/token.rb b/lib/json_web_token/token.rb
index 5b67715b0b2ea48c8604b9ddd564a93da5914855..ce5d6f248d0131b7087367b452fcae78ac7c4a26 100644
--- a/lib/json_web_token/token.rb
+++ b/lib/json_web_token/token.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module JSONWebToken
   class Token
     attr_accessor :issuer, :subject, :audience, :id
diff --git a/lib/mattermost/client.rb b/lib/mattermost/client.rb
index d80cd7d2a4e477eab040ca9884ae40690c55df52..293d0c563c5c35a45fbe8f546232461074d91775 100644
--- a/lib/mattermost/client.rb
+++ b/lib/mattermost/client.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Mattermost
   ClientError = Class.new(Mattermost::Error)
 
diff --git a/lib/mattermost/command.rb b/lib/mattermost/command.rb
index 704813dfdf0dd3695fc117a73e0f5d49e77e0e7b..a02745486d6470e421d28a044b2e8553384e6d2c 100644
--- a/lib/mattermost/command.rb
+++ b/lib/mattermost/command.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Mattermost
   class Command < Client
     def create(params)
diff --git a/lib/mattermost/error.rb b/lib/mattermost/error.rb
index dee6deb7974861661d9f30838a7a7fdc3d23d42d..054bd5457bde5ba18ab673286cb9cc59aeb909f4 100644
--- a/lib/mattermost/error.rb
+++ b/lib/mattermost/error.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Mattermost
   Error = Class.new(StandardError)
 end
diff --git a/lib/mattermost/session.rb b/lib/mattermost/session.rb
index 2aa7a2f64d8e150a40b1f85e4b8d6b6aecfd3b23..e2083848a8dbb8a10085a996c580fd0209e06b2b 100644
--- a/lib/mattermost/session.rb
+++ b/lib/mattermost/session.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Mattermost
   class NoSessionError < Mattermost::Error
     def message
diff --git a/lib/mattermost/team.rb b/lib/mattermost/team.rb
index 95c2f6f9d6b244a056a415750a01785820087f49..58120178f505eefabf3dd1925628a4ca65065102 100644
--- a/lib/mattermost/team.rb
+++ b/lib/mattermost/team.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Mattermost
   class Team < Client
     # Returns all teams that the current user is a member of
diff --git a/lib/microsoft_teams/activity.rb b/lib/microsoft_teams/activity.rb
index d2c420efdafa506f4ce9a4aa793edd2fa4514126..207e90d263800a88aa1d10508ea93f651c8653c4 100644
--- a/lib/microsoft_teams/activity.rb
+++ b/lib/microsoft_teams/activity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module MicrosoftTeams
   class Activity
     def initialize(title:, subtitle:, text:, image:)
diff --git a/lib/microsoft_teams/notifier.rb b/lib/microsoft_teams/notifier.rb
index 226ee1373db0b231b4d9eff0765a0cfb4f497a1b..c7dec09ba6b2fa067addf30cf04d85a701ae69b1 100644
--- a/lib/microsoft_teams/notifier.rb
+++ b/lib/microsoft_teams/notifier.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module MicrosoftTeams
   class Notifier
     def initialize(webhook)
diff --git a/lib/object_storage/direct_upload.rb b/lib/object_storage/direct_upload.rb
index 97f56e10ccf5d28fea23f35c93dbf13d6b882ca7..fd26663fef027dcd092be5e2c823c030633c37d6 100644
--- a/lib/object_storage/direct_upload.rb
+++ b/lib/object_storage/direct_upload.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ObjectStorage
   #
   # The DirectUpload c;ass generates a set of presigned URLs
diff --git a/lib/omni_auth/strategies/bitbucket.rb b/lib/omni_auth/strategies/bitbucket.rb
index ce1bdfe6ee44c36e0261d9adb45d1ece9469acef..6c914b4222af4e332ad071306fa1b1b609437b53 100644
--- a/lib/omni_auth/strategies/bitbucket.rb
+++ b/lib/omni_auth/strategies/bitbucket.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'omniauth-oauth2'
 
 module OmniAuth
diff --git a/lib/omni_auth/strategies/jwt.rb b/lib/omni_auth/strategies/jwt.rb
index ebdb5c7faf0b65901ce3b7089e6865ec75aded07..a792903fde7f1f71edbdca15d0d66f58c8f11ca2 100644
--- a/lib/omni_auth/strategies/jwt.rb
+++ b/lib/omni_auth/strategies/jwt.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'omniauth'
 require 'jwt'
 
diff --git a/lib/peek/rblineprof/custom_controller_helpers.rb b/lib/peek/rblineprof/custom_controller_helpers.rb
index 9beb442bfa397cc5a8802d51704d9cd288c711d9..581cc6a37b43c57041b2b0ad37fab94fa3373136 100644
--- a/lib/peek/rblineprof/custom_controller_helpers.rb
+++ b/lib/peek/rblineprof/custom_controller_helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Peek
   module Rblineprof
     module CustomControllerHelpers
@@ -41,7 +43,7 @@ def inject_rblineprof
             ]
           end.sort_by{ |a,b,c,d,e,f| -f }
 
-          output = "<div class='modal-dialog modal-xl'><div class='modal-content'>"
+          output = ["<div class='modal-dialog modal-xl'><div class='modal-content'>"]
           output << "<div class='modal-header'>"
           output << "<h4>Line profiling: #{human_description(params[:lineprofiler])}</h4>"
           output << "<button class='close' type='button' data-dismiss='modal' aria-label='close'><span aria-hidden='true'>&times;</span></button>"
@@ -93,7 +95,7 @@ def inject_rblineprof
 
           output << "</div></div></div>"
 
-          response.body += "<div class='modal' id='modal-peek-line-profile' tabindex=-1>#{output}</div>".html_safe
+          response.body += "<div class='modal' id='modal-peek-line-profile' tabindex=-1>#{output.join}</div>".html_safe
         end
 
         ret
diff --git a/lib/peek/views/gitaly.rb b/lib/peek/views/gitaly.rb
index ab35f7a2258914f27f5302caf209d3ae0025e921..860963ef94fde8834c31b57f283c364c5ae11bdc 100644
--- a/lib/peek/views/gitaly.rb
+++ b/lib/peek/views/gitaly.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Peek
   module Views
     class Gitaly < View
diff --git a/lib/peek/views/host.rb b/lib/peek/views/host.rb
index 43c8a35c7ea00f2f223652c48f4630485c03491f..da0816b364cad15c4c58444aadbb078e964ca895 100644
--- a/lib/peek/views/host.rb
+++ b/lib/peek/views/host.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Peek
   module Views
     class Host < View
diff --git a/lib/rouge/formatters/html_gitlab.rb b/lib/rouge/formatters/html_gitlab.rb
index e877ab1024839965cf7290bd0c5534900a9b751e..e2a7d3ef5bafd0956724820ab06b0db50f9d0c67 100644
--- a/lib/rouge/formatters/html_gitlab.rb
+++ b/lib/rouge/formatters/html_gitlab.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Rouge
   module Formatters
     class HTMLGitlab < Rouge::Formatters::HTML
diff --git a/lib/rouge/plugins/common_mark.rb b/lib/rouge/plugins/common_mark.rb
index 8f9de061124b70bb11d63290a99c70473f49cad2..d240df5a0e01c3d798b929a04d92be178ea16c5c 100644
--- a/lib/rouge/plugins/common_mark.rb
+++ b/lib/rouge/plugins/common_mark.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # A rouge plugin for CommonMark markdown engine.
 # Used to highlight code generated by CommonMark.
 
diff --git a/lib/rspec_flaky/config.rb b/lib/rspec_flaky/config.rb
index 06e96f969f130fedff9aa6d20674eb540877e19e..55c1d4747b4cbd841a2d9948bde46a0980da7d3d 100644
--- a/lib/rspec_flaky/config.rb
+++ b/lib/rspec_flaky/config.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module RspecFlaky
   class Config
     def self.generate_report?
diff --git a/lib/rspec_flaky/example.rb b/lib/rspec_flaky/example.rb
index b6e790cbbab4ae71ad82bcc82ade71530c4003fb..3c1b05257a02b47dafaf59d9a8390b9337cae30b 100644
--- a/lib/rspec_flaky/example.rb
+++ b/lib/rspec_flaky/example.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module RspecFlaky
   # This is a wrapper class for RSpec::Core::Example
   class Example
diff --git a/lib/rspec_flaky/flaky_example.rb b/lib/rspec_flaky/flaky_example.rb
index 6be24014d897bd2f811c54a1ed97603279db624b..da5dbf06bc937df2847b745e43261200c1866552 100644
--- a/lib/rspec_flaky/flaky_example.rb
+++ b/lib/rspec_flaky/flaky_example.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module RspecFlaky
   # This represents a flaky RSpec example and is mainly meant to be saved in a JSON file
   class FlakyExample < OpenStruct
diff --git a/lib/rspec_flaky/flaky_examples_collection.rb b/lib/rspec_flaky/flaky_examples_collection.rb
index dea23c325be9803a54f0fab450123ddd77479ada..290a51766e9c3bcfdb2ca2486f2f5a03dccd3f7f 100644
--- a/lib/rspec_flaky/flaky_examples_collection.rb
+++ b/lib/rspec_flaky/flaky_examples_collection.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'active_support/hash_with_indifferent_access'
 
 require_relative 'flaky_example'
diff --git a/lib/rspec_flaky/listener.rb b/lib/rspec_flaky/listener.rb
index 9cd0c38cb5547f7da2ce9a9245cd82c17821ee2d..19cc0baa2d3239f79da0bde7030c79c7bb14c4e1 100644
--- a/lib/rspec_flaky/listener.rb
+++ b/lib/rspec_flaky/listener.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'json'
 
 require_dependency 'rspec_flaky/config'
diff --git a/lib/rspec_flaky/report.rb b/lib/rspec_flaky/report.rb
index 1c362fdd20d453f2f9e4147e7403e094f7190109..9a0fb88c42432b7a0a2804c4896aa036c4fe48c0 100644
--- a/lib/rspec_flaky/report.rb
+++ b/lib/rspec_flaky/report.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'json'
 require 'time'
 
diff --git a/lib/system_check/app/active_users_check.rb b/lib/system_check/app/active_users_check.rb
index 1d72c8d69034cc469d8401a7b3a74fc08a589ee8..8446c2fc2c874c28b343dd7a895ba3f39ae54733 100644
--- a/lib/system_check/app/active_users_check.rb
+++ b/lib/system_check/app/active_users_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class ActiveUsersCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/database_config_exists_check.rb b/lib/system_check/app/database_config_exists_check.rb
index d1fae192350e49d14336f64c0060fc6de42330ee..1769145ed637838b4d7347deeb6c612e849ecbea 100644
--- a/lib/system_check/app/database_config_exists_check.rb
+++ b/lib/system_check/app/database_config_exists_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class DatabaseConfigExistsCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/git_config_check.rb b/lib/system_check/app/git_config_check.rb
index d08a81639e3f8c7ba60414892dd81c66f78e1c82..4e8d607096cb758358555f44552905e2eb6446b9 100644
--- a/lib/system_check/app/git_config_check.rb
+++ b/lib/system_check/app/git_config_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class GitConfigCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/git_user_default_ssh_config_check.rb b/lib/system_check/app/git_user_default_ssh_config_check.rb
index ad41760dff2b8ff701c38aafdde33cde2279315d..6cd53779bfdffa7fe1531dad7a8f5de44de826ae 100644
--- a/lib/system_check/app/git_user_default_ssh_config_check.rb
+++ b/lib/system_check/app/git_user_default_ssh_config_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class GitUserDefaultSSHConfigCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/git_version_check.rb b/lib/system_check/app/git_version_check.rb
index 44ec888c19765b24104caed859912b754f478919..994af3ab53e7b91fd26cfbf3161527d2364c9130 100644
--- a/lib/system_check/app/git_version_check.rb
+++ b/lib/system_check/app/git_version_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class GitVersionCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/gitlab_config_exists_check.rb b/lib/system_check/app/gitlab_config_exists_check.rb
index 247aa0994e4f1471c67cfb901d6352bf661ed417..1cc5ead0d891fee7895c9ff95ffa2814f97f3602 100644
--- a/lib/system_check/app/gitlab_config_exists_check.rb
+++ b/lib/system_check/app/gitlab_config_exists_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class GitlabConfigExistsCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/gitlab_config_up_to_date_check.rb b/lib/system_check/app/gitlab_config_up_to_date_check.rb
index c609e48e133655ff137abc94490de322a7de5457..58c7e3039c88155aabb65dd7c2ee01bdf257f406 100644
--- a/lib/system_check/app/gitlab_config_up_to_date_check.rb
+++ b/lib/system_check/app/gitlab_config_up_to_date_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class GitlabConfigUpToDateCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/init_script_exists_check.rb b/lib/system_check/app/init_script_exists_check.rb
index d246e058e86d959122e309e2b3c9a6a237fa45e8..d36dbe7d67dee07ca847c4019fc6f973ceeb06d2 100644
--- a/lib/system_check/app/init_script_exists_check.rb
+++ b/lib/system_check/app/init_script_exists_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class InitScriptExistsCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/init_script_up_to_date_check.rb b/lib/system_check/app/init_script_up_to_date_check.rb
index 53a47eb0f42cc537151e25097dd1f8f2779e69e2..569c41df6e4c212b7af250b092db4d9a9a1710de 100644
--- a/lib/system_check/app/init_script_up_to_date_check.rb
+++ b/lib/system_check/app/init_script_up_to_date_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class InitScriptUpToDateCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/log_writable_check.rb b/lib/system_check/app/log_writable_check.rb
index 3e0c436d6eecada871e8ba721321791614c80f7a..e26ad143eb82a8827e9ee819a1af19ce493938ad 100644
--- a/lib/system_check/app/log_writable_check.rb
+++ b/lib/system_check/app/log_writable_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class LogWritableCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/migrations_are_up_check.rb b/lib/system_check/app/migrations_are_up_check.rb
index 5eedbacce77cd9e84769d47a849ae3ed45677944..b12e9ac6bbac78ccc6f2e40ce7acab563371b4b8 100644
--- a/lib/system_check/app/migrations_are_up_check.rb
+++ b/lib/system_check/app/migrations_are_up_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class MigrationsAreUpCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/orphaned_group_members_check.rb b/lib/system_check/app/orphaned_group_members_check.rb
index 2b46d36fe517440a77802ac9bc9ed2f13db498db..3e6ffb8190b83fcd15c4ce0abe7ea6a7d850f07a 100644
--- a/lib/system_check/app/orphaned_group_members_check.rb
+++ b/lib/system_check/app/orphaned_group_members_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class OrphanedGroupMembersCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/projects_have_namespace_check.rb b/lib/system_check/app/projects_have_namespace_check.rb
index a6ec9f7665c7871731196644d25ba0d5a488768f..2bf2529acf1452d51901642b6ccaa4c7a7ddb110 100644
--- a/lib/system_check/app/projects_have_namespace_check.rb
+++ b/lib/system_check/app/projects_have_namespace_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class ProjectsHaveNamespaceCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/redis_version_check.rb b/lib/system_check/app/redis_version_check.rb
index a0610e73576cd1b9ccc4bcfe99a94eb89c870f1d..890f8b44d13ba3c3800e162d0870eafb4099bf3f 100644
--- a/lib/system_check/app/redis_version_check.rb
+++ b/lib/system_check/app/redis_version_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class RedisVersionCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/ruby_version_check.rb b/lib/system_check/app/ruby_version_check.rb
index 57bbabece1fed6a196cf16f289da478256ef0a80..d73c39f2c3f243f9e5284722ede7b61992c32f92 100644
--- a/lib/system_check/app/ruby_version_check.rb
+++ b/lib/system_check/app/ruby_version_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class RubyVersionCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/tmp_writable_check.rb b/lib/system_check/app/tmp_writable_check.rb
index 99a75e57abf3cc25a8eef038f6cbe764ebd006aa..6687df091d354814f677b8551b8844d70bed86fa 100644
--- a/lib/system_check/app/tmp_writable_check.rb
+++ b/lib/system_check/app/tmp_writable_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class TmpWritableCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/uploads_directory_exists_check.rb b/lib/system_check/app/uploads_directory_exists_check.rb
index 7026d0ba0755a4a4d7b06421a07f8371c65dc3b0..940eff9d4cf055a5f637b57ee9c4a29f74e01f5e 100644
--- a/lib/system_check/app/uploads_directory_exists_check.rb
+++ b/lib/system_check/app/uploads_directory_exists_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class UploadsDirectoryExistsCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/uploads_path_permission_check.rb b/lib/system_check/app/uploads_path_permission_check.rb
index 7df6c060254ef4d25dc1d2cc506c596e361139f3..4a49f3bc2bb6b3a01a090ec016022bc0ca3767b9 100644
--- a/lib/system_check/app/uploads_path_permission_check.rb
+++ b/lib/system_check/app/uploads_path_permission_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class UploadsPathPermissionCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/app/uploads_path_tmp_permission_check.rb b/lib/system_check/app/uploads_path_tmp_permission_check.rb
index b276a81eac119bb72cff84c0a473ccbfb135415b..ae374f4707c7455f4ea901faae3935ae2bc2e3b4 100644
--- a/lib/system_check/app/uploads_path_tmp_permission_check.rb
+++ b/lib/system_check/app/uploads_path_tmp_permission_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module App
     class UploadsPathTmpPermissionCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/base_check.rb b/lib/system_check/base_check.rb
index 0f5742dd67f84f8dcc694f4ea1bd4c8547364686..e06245294c4287c890522df94a3b2346e685cb2f 100644
--- a/lib/system_check/base_check.rb
+++ b/lib/system_check/base_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   # Base class for Checks. You must inherit from here
   # and implement the methods below when necessary
diff --git a/lib/system_check/helpers.rb b/lib/system_check/helpers.rb
index 6227e461d24c5df6ce7d8cb6e0e814a9c3501976..07d479848fe82190fdeff5fb9a16148898327030 100644
--- a/lib/system_check/helpers.rb
+++ b/lib/system_check/helpers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module Helpers
     include ::Gitlab::TaskHelpers
diff --git a/lib/system_check/incoming_email/foreman_configured_check.rb b/lib/system_check/incoming_email/foreman_configured_check.rb
index 1db7bf2b78221abac8b74432e5d9007a04cc27e1..944913087da8b2dcf4833fc9d2d36db21343db53 100644
--- a/lib/system_check/incoming_email/foreman_configured_check.rb
+++ b/lib/system_check/incoming_email/foreman_configured_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module IncomingEmail
     class ForemanConfiguredCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/incoming_email/imap_authentication_check.rb b/lib/system_check/incoming_email/imap_authentication_check.rb
index 3550c5796b039cea6b315d76824466a718edbb36..613c229637586bc1a317f52631489a987b7ee54f 100644
--- a/lib/system_check/incoming_email/imap_authentication_check.rb
+++ b/lib/system_check/incoming_email/imap_authentication_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module IncomingEmail
     class ImapAuthenticationCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/incoming_email/initd_configured_check.rb b/lib/system_check/incoming_email/initd_configured_check.rb
index ea23b8ef49c2853fdd0aabd0de5e9d399f53acfa..acb4b5a9e748a9e2d087a6789cee55df934e0557 100644
--- a/lib/system_check/incoming_email/initd_configured_check.rb
+++ b/lib/system_check/incoming_email/initd_configured_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module IncomingEmail
     class InitdConfiguredCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/incoming_email/mail_room_running_check.rb b/lib/system_check/incoming_email/mail_room_running_check.rb
index c1807501829b1cddc61d60e7be3ad9bd91347fb4..b7aead4624edc4ac32152c17dd311a1a695f62b7 100644
--- a/lib/system_check/incoming_email/mail_room_running_check.rb
+++ b/lib/system_check/incoming_email/mail_room_running_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module IncomingEmail
     class MailRoomRunningCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/orphans/namespace_check.rb b/lib/system_check/orphans/namespace_check.rb
index 09b57c7b408fa2361480099c6374ec78d75946c8..53b2d8fd5b33a61dd6a4a68942f7ff714ddb58e4 100644
--- a/lib/system_check/orphans/namespace_check.rb
+++ b/lib/system_check/orphans/namespace_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module Orphans
     class NamespaceCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/orphans/repository_check.rb b/lib/system_check/orphans/repository_check.rb
index 2695c658874e014a8605fb0f4cb7f5b23464bbaf..ef8fe945f6115fe7853bacc677c1f109d8e7ebd8 100644
--- a/lib/system_check/orphans/repository_check.rb
+++ b/lib/system_check/orphans/repository_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   module Orphans
     class RepositoryCheck < SystemCheck::BaseCheck
diff --git a/lib/system_check/simple_executor.rb b/lib/system_check/simple_executor.rb
index 99c9e9841071decab20a6b89206e67a4eee4f541..11818ae54f8339e8b40a8b4c6b1be58cb8aa880c 100644
--- a/lib/system_check/simple_executor.rb
+++ b/lib/system_check/simple_executor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SystemCheck
   # Simple Executor is current default executor for GitLab
   # It is a simple port from display logic in the old check.rake