diff --git a/Library/Homebrew/cli/args.rb b/Library/Homebrew/cli/args.rb
index 49a9940541..3f2dc9de8c 100644
--- a/Library/Homebrew/cli/args.rb
+++ b/Library/Homebrew/cli/args.rb
@@ -152,3 +152,5 @@ module Homebrew
     end
   end
 end
+
+require "extend/os/args"
diff --git a/Library/Homebrew/cli/parser.rb b/Library/Homebrew/cli/parser.rb
index 4fc804ad65..a507451f25 100644
--- a/Library/Homebrew/cli/parser.rb
+++ b/Library/Homebrew/cli/parser.rb
@@ -341,14 +341,20 @@ module Homebrew
 
         @args_parsed = true
 
-        if !ignore_invalid_options && @args.help?
-          puts generate_help_text
-          exit
+        unless ignore_invalid_options
+          if @args.help?
+            puts generate_help_text
+            exit
+          end
+
+          validate_options
         end
 
         @args
       end
 
+      def validate_options; end
+
       def generate_help_text
         Formatter.format_help_text(@parser.to_s, width: COMMAND_DESC_WIDTH)
                  .gsub(/\n.*?@@HIDDEN@@.*?(?=\n)/, "")
@@ -701,3 +707,5 @@ module Homebrew
     end
   end
 end
+
+require "extend/os/parser"
diff --git a/Library/Homebrew/extend/os/args.rb b/Library/Homebrew/extend/os/args.rb
new file mode 100644
index 0000000000..e497060e41
--- /dev/null
+++ b/Library/Homebrew/extend/os/args.rb
@@ -0,0 +1,4 @@
+# typed: false
+# frozen_string_literal: true
+
+require "extend/os/linux/args" if OS.linux?
diff --git a/Library/Homebrew/extend/os/linux/args.rb b/Library/Homebrew/extend/os/linux/args.rb
new file mode 100644
index 0000000000..1d4b221909
--- /dev/null
+++ b/Library/Homebrew/extend/os/linux/args.rb
@@ -0,0 +1,17 @@
+# typed: false
+# frozen_string_literal: true
+
+module Homebrew
+  module CLI
+    class Args
+      undef only_formula_or_cask
+
+      def only_formula_or_cask
+        # Make formula the default on linux for non-developers
+        return :formula unless Homebrew::EnvConfig.developer?
+        return :formula if formula? && !cask?
+        return :cask if cask? && !formula?
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/extend/os/linux/parser.rb b/Library/Homebrew/extend/os/linux/parser.rb
new file mode 100644
index 0000000000..939585859d
--- /dev/null
+++ b/Library/Homebrew/extend/os/linux/parser.rb
@@ -0,0 +1,20 @@
+# typed: false
+# frozen_string_literal: true
+
+module Homebrew
+  module CLI
+    class Parser
+      undef validate_options
+
+      def validate_options
+        return unless @args.respond_to?(:cask?)
+        return unless @args.cask?
+
+        msg = "Casks are not supported on Linux"
+        raise UsageError, msg unless Homebrew::EnvConfig.developer?
+
+        opoo msg unless @args.quiet?
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/extend/os/parser.rb b/Library/Homebrew/extend/os/parser.rb
new file mode 100644
index 0000000000..90b0d42da7
--- /dev/null
+++ b/Library/Homebrew/extend/os/parser.rb
@@ -0,0 +1,4 @@
+# typed: false
+# frozen_string_literal: true
+
+require "extend/os/linux/parser" if OS.linux?
diff --git a/Library/Homebrew/test/cli/named_args_spec.rb b/Library/Homebrew/test/cli/named_args_spec.rb
index 06e85a7344..6b2e8d2418 100644
--- a/Library/Homebrew/test/cli/named_args_spec.rb
+++ b/Library/Homebrew/test/cli/named_args_spec.rb
@@ -67,7 +67,7 @@ describe Homebrew::CLI::NamedArgs do
   end
 
   describe "#to_formulae_and_casks" do
-    it "returns formulae and casks" do
+    it "returns formulae and casks", :dev_on_linux do
       stub_formula_loader foo, call_original: true
       stub_cask_loader baz, call_original: true
 
@@ -118,7 +118,13 @@ describe Homebrew::CLI::NamedArgs do
       expect { described_class.new("foo").to_formulae_and_casks }.to raise_error(FormulaOrCaskUnavailableError)
     end
 
-    it "returns formula when formula is present and cask is unreadable" do
+    it "raises an error when formula is absent and cask is available on linux", :needs_linux do
+      stub_cask_loader foo_cask
+
+      expect { described_class.new("foo").to_formulae_and_casks }.to raise_error(FormulaUnavailableError)
+    end
+
+    it "returns formula when formula is present and cask is unreadable", :dev_on_linux do
       stub_formula_loader foo
       setup_unredable_cask "foo"
 
@@ -126,7 +132,7 @@ describe Homebrew::CLI::NamedArgs do
       expect { described_class.new("foo").to_formulae_and_casks }.to output(/Failed to load cask: foo/).to_stderr
     end
 
-    it "returns cask when formula is unreadable and cask is present" do
+    it "returns cask when formula is unreadable and cask is present", :dev_on_linux do
       setup_unredable_formula "foo"
       stub_cask_loader foo_cask
 
@@ -134,7 +140,7 @@ describe Homebrew::CLI::NamedArgs do
       expect { described_class.new("foo").to_formulae_and_casks }.to output(/Failed to load formula: foo/).to_stderr
     end
 
-    it "raises an error when formula is absent and cask is unreadable" do
+    it "raises an error when formula is absent and cask is unreadable", :dev_on_linux do
       setup_unredable_cask "foo"
 
       expect { described_class.new("foo").to_formulae_and_casks }.to raise_error(Cask::CaskUnreadableError)
@@ -156,7 +162,7 @@ describe Homebrew::CLI::NamedArgs do
   end
 
   describe "#to_resolved_formulae_to_casks" do
-    it "returns resolved formulae, as well as casks" do
+    it "returns resolved formulae, as well as casks", :dev_on_linux do
       allow(Formulary).to receive(:resolve).and_call_original
       allow(Formulary).to receive(:resolve).with("foo", any_args).and_return foo
       stub_cask_loader baz, call_original: true
@@ -245,7 +251,7 @@ describe Homebrew::CLI::NamedArgs do
       (HOMEBREW_CELLAR/"foo/1.0").mkpath
     end
 
-    it "returns kegs, as well as casks" do
+    it "returns kegs, as well as casks", :dev_on_linux do
       stub_cask_loader baz, call_original: true
 
       kegs, casks = described_class.new("foo", "baz").to_kegs_to_casks
@@ -279,7 +285,7 @@ describe Homebrew::CLI::NamedArgs do
       allow(Cask::CaskLoader).to receive(:path).and_call_original
     end
 
-    it "returns taps, cask formula and existing paths" do
+    it "returns taps, cask formula and existing paths", :dev_on_linux do
       expect(Formulary).to receive(:path).with("foo").and_return(formula_path)
       expect(Cask::CaskLoader).to receive(:path).with("baz").and_return(cask_path)
 
@@ -287,7 +293,7 @@ describe Homebrew::CLI::NamedArgs do
         .to eq [Tap.fetch("homebrew/core").path, formula_path, cask_path, existing_path]
     end
 
-    it "returns both cask and formula paths if they exist" do
+    it "returns both cask and formula paths if they exist", :dev_on_linux do
       expect(Formulary).to receive(:path).with("foo").and_return(formula_path)
       expect(Cask::CaskLoader).to receive(:path).with("baz").and_return(cask_path)
 
@@ -305,6 +311,12 @@ describe Homebrew::CLI::NamedArgs do
 
       expect(described_class.new("foo", "baz").to_paths(only: :cask)).to eq [cask_path, Cask::CaskLoader.path("baz")]
     end
+
+    it "returns only formulae by default on linux", :needs_linux do
+      expect(Formulary).to receive(:path).with("foo").and_return(formula_path)
+
+      expect(described_class.new("foo", "baz").to_paths).to eq [formula_path, Formulary.path("baz")]
+    end
   end
 
   describe "#to_taps" do
diff --git a/Library/Homebrew/test/cli/parser_spec.rb b/Library/Homebrew/test/cli/parser_spec.rb
index 5aaab4683a..408295d91c 100644
--- a/Library/Homebrew/test/cli/parser_spec.rb
+++ b/Library/Homebrew/test/cli/parser_spec.rb
@@ -562,4 +562,20 @@ describe Homebrew::CLI::Parser do
       expect { parser.parse(["--not-a-command"]) }.to raise_error(OptionParser::InvalidOption, /--not-a-command/)
     end
   end
+
+  describe "--cask on linux", :needs_linux do
+    subject(:parser) do
+      described_class.new do
+        switch "--cask"
+      end
+    end
+
+    it "throws an error by default" do
+      expect { parser.parse(["--cask"]) }.to raise_error UsageError, /Casks are not supported on Linux/
+    end
+
+    it "only warns developers", :dev_on_linux do
+      expect { parser.parse(["--cask"]) }.not_to raise_error
+    end
+  end
 end
diff --git a/Library/Homebrew/test/cmd/--cache_spec.rb b/Library/Homebrew/test/cmd/--cache_spec.rb
index 410ca72f18..ca221f626a 100644
--- a/Library/Homebrew/test/cmd/--cache_spec.rb
+++ b/Library/Homebrew/test/cmd/--cache_spec.rb
@@ -9,7 +9,6 @@ describe "brew --cache" do
   it "prints all cache files for a given Formula", :integration_test do
     expect { brew "--cache", testball }
       .to output(%r{#{HOMEBREW_CACHE}/downloads/[\da-f]{64}--testball-}o).to_stdout
-      .and output(/Treating #{Regexp.escape(testball)} as a formula/).to_stderr
       .and be_a_success
     expect { brew "--cache", "--formula", testball }
       .to output(%r{#{HOMEBREW_CACHE}/downloads/[\da-f]{64}--testball-}o).to_stdout
@@ -17,7 +16,7 @@ describe "brew --cache" do
       .and be_a_success
   end
 
-  it "prints the cache files for a given Cask", :integration_test do
+  it "prints the cache files for a given Cask", :integration_test, :needs_macos do
     expect { brew "--cache", cask_path("local-caffeine") }
       .to output(%r{#{HOMEBREW_CACHE}/downloads/[\da-f]{64}--caffeine\.zip}o).to_stdout
       .and output(/Treating #{Regexp.escape(cask_path("local-caffeine"))} as a cask/).to_stderr
@@ -28,7 +27,7 @@ describe "brew --cache" do
       .and be_a_success
   end
 
-  it "prints the cache files for a given Formula and Cask", :integration_test do
+  it "prints the cache files for a given Formula and Cask", :integration_test, :needs_macos do
     expect { brew "--cache", testball, cask_path("local-caffeine") }
       .to output(
         %r{
diff --git a/Library/Homebrew/test/cmd/home_spec.rb b/Library/Homebrew/test/cmd/home_spec.rb
index 063846c334..3845ac3859 100644
--- a/Library/Homebrew/test/cmd/home_spec.rb
+++ b/Library/Homebrew/test/cmd/home_spec.rb
@@ -34,7 +34,7 @@ describe "brew home" do
       .and be_a_success
   end
 
-  it "opens the homepage for a given Cask", :integration_test do
+  it "opens the homepage for a given Cask", :integration_test, :needs_macos do
     expect { brew "home", local_caffeine_path, "HOMEBREW_BROWSER" => "echo" }
       .to output(/#{local_caffeine_homepage}/).to_stdout
       .and output(/Treating #{Regexp.escape(local_caffeine_path)} as a cask/).to_stderr
@@ -45,7 +45,7 @@ describe "brew home" do
       .and be_a_success
   end
 
-  it "opens the homepages for a given formula and Cask", :integration_test do
+  it "opens the homepages for a given formula and Cask", :integration_test, :needs_macos do
     setup_test_formula "testballhome"
 
     expect { brew "home", "testballhome", local_caffeine_path, "HOMEBREW_BROWSER" => "echo" }
diff --git a/Library/Homebrew/test/spec_helper.rb b/Library/Homebrew/test/spec_helper.rb
index 2aef66d976..769f737ce6 100644
--- a/Library/Homebrew/test/spec_helper.rb
+++ b/Library/Homebrew/test/spec_helper.rb
@@ -180,6 +180,10 @@ RSpec.configure do |config|
     skip "Unzip is not installed." unless which("unzip")
   end
 
+  config.before(:each, :dev_on_linux) do
+    allow(Homebrew::EnvConfig).to receive(:developer?).and_return(true) if OS.linux?
+  end
+
   config.around do |example|
     def find_files
       return [] unless File.exist?(TEST_TMPDIR)