diff --git a/payload_generator/ab_generator_unittest.cc b/payload_generator/ab_generator_unittest.cc
index 2f8c0c6..170e0e3 100644
--- a/payload_generator/ab_generator_unittest.cc
+++ b/payload_generator/ab_generator_unittest.cc
@@ -30,10 +30,10 @@
 #include "update_engine/common/test_utils.h"
 #include "update_engine/common/utils.h"
 #include "update_engine/payload_generator/annotated_operation.h"
-#include "update_engine/payload_generator/bzip.h"
 #include "update_engine/payload_generator/delta_diff_generator.h"
 #include "update_engine/payload_generator/extent_ranges.h"
 #include "update_engine/payload_generator/extent_utils.h"
+#include "update_engine/payload_generator/xz.h"
 
 using std::string;
 using std::vector;
@@ -48,8 +48,8 @@
   return ext.start_block() == start_block && ext.num_blocks() == num_blocks;
 }
 
-// Tests splitting of a REPLACE/REPLACE_BZ operation.
-void TestSplitReplaceOrReplaceBzOperation(InstallOperation_Type orig_type,
+// Tests splitting of a REPLACE/REPLACE_XZ operation.
+void TestSplitReplaceOrReplaceXzOperation(InstallOperation_Type orig_type,
                                           bool compressible) {
   const size_t op_ex1_start_block = 2;
   const size_t op_ex1_num_blocks = 2;
@@ -71,7 +71,7 @@
   }
   ASSERT_EQ(part_size, part_data.size());
   test_utils::ScopedTempFile part_file(
-      "SplitReplaceOrReplaceBzTest_part.XXXXXX");
+      "SplitReplaceOrReplaceXzTest_part.XXXXXX");
   ASSERT_TRUE(test_utils::WriteFileVector(part_file.path(), part_data));
 
   // Create original operation and blob data.
@@ -97,7 +97,7 @@
   if (orig_type == InstallOperation::REPLACE) {
     op_blob = op_data;
   } else {
-    ASSERT_TRUE(BzipCompress(op_data, &op_blob));
+    ASSERT_TRUE(XzCompress(op_data, &op_blob));
   }
   op.set_data_offset(0);
   op.set_data_length(op_blob.size());
@@ -108,7 +108,7 @@
 
   // Create the data file.
   test_utils::ScopedTempFile data_file(
-      "SplitReplaceOrReplaceBzTest_data.XXXXXX");
+      "SplitReplaceOrReplaceXzTest_data.XXXXXX");
   EXPECT_TRUE(test_utils::WriteFileVector(data_file.path(), op_blob));
   int data_fd = open(data_file.path().c_str(), O_RDWR, 000);
   EXPECT_GE(data_fd, 0);
@@ -118,14 +118,14 @@
 
   // Split the operation.
   vector<AnnotatedOperation> result_ops;
-  PayloadVersion version(kChromeOSMajorPayloadVersion,
+  PayloadVersion version(kBrilloMajorPayloadVersion,
                          kSourceMinorPayloadVersion);
   ASSERT_TRUE(ABGenerator::SplitAReplaceOp(
       version, aop, part_file.path(), &result_ops, &blob_file));
 
   // Check the result.
   InstallOperation_Type expected_type =
-      compressible ? InstallOperation::REPLACE_BZ : InstallOperation::REPLACE;
+      compressible ? InstallOperation::REPLACE_XZ : InstallOperation::REPLACE;
 
   ASSERT_EQ(2U, result_ops.size());
 
@@ -143,7 +143,7 @@
       part_data.begin() + op_ex1_offset + op_ex1_size);
   brillo::Blob first_expected_blob;
   if (compressible) {
-    ASSERT_TRUE(BzipCompress(first_expected_data, &first_expected_blob));
+    ASSERT_TRUE(XzCompress(first_expected_data, &first_expected_blob));
   } else {
     first_expected_blob = first_expected_data;
   }
@@ -173,7 +173,7 @@
       part_data.begin() + op_ex2_offset + op_ex2_size);
   brillo::Blob second_expected_blob;
   if (compressible) {
-    ASSERT_TRUE(BzipCompress(second_expected_data, &second_expected_blob));
+    ASSERT_TRUE(XzCompress(second_expected_data, &second_expected_blob));
   } else {
     second_expected_blob = second_expected_data;
   }
@@ -199,8 +199,8 @@
   }
 }
 
-// Tests merging of REPLACE/REPLACE_BZ operations.
-void TestMergeReplaceOrReplaceBzOperations(InstallOperation_Type orig_type,
+// Tests merging of REPLACE/REPLACE_XZ operations.
+void TestMergeReplaceOrReplaceXzOperations(InstallOperation_Type orig_type,
                                            bool compressible) {
   const size_t first_op_num_blocks = 1;
   const size_t second_op_num_blocks = 2;
@@ -221,7 +221,7 @@
   }
   ASSERT_EQ(part_size, part_data.size());
   test_utils::ScopedTempFile part_file(
-      "MergeReplaceOrReplaceBzTest_part.XXXXXX");
+      "MergeReplaceOrReplaceXzTest_part.XXXXXX");
   ASSERT_TRUE(test_utils::WriteFileVector(part_file.path(), part_data));
 
   // Create original operations and blob data.
@@ -239,7 +239,7 @@
   if (orig_type == InstallOperation::REPLACE) {
     first_op_blob = first_op_data;
   } else {
-    ASSERT_TRUE(BzipCompress(first_op_data, &first_op_blob));
+    ASSERT_TRUE(XzCompress(first_op_data, &first_op_blob));
   }
   first_op.set_data_offset(0);
   first_op.set_data_length(first_op_blob.size());
@@ -259,7 +259,7 @@
   if (orig_type == InstallOperation::REPLACE) {
     second_op_blob = second_op_data;
   } else {
-    ASSERT_TRUE(BzipCompress(second_op_data, &second_op_blob));
+    ASSERT_TRUE(XzCompress(second_op_data, &second_op_blob));
   }
   second_op.set_data_offset(first_op_blob.size());
   second_op.set_data_length(second_op_blob.size());
@@ -272,7 +272,7 @@
 
   // Create the data file.
   test_utils::ScopedTempFile data_file(
-      "MergeReplaceOrReplaceBzTest_data.XXXXXX");
+      "MergeReplaceOrReplaceXzTest_data.XXXXXX");
   EXPECT_TRUE(test_utils::WriteFileVector(data_file.path(), blob_data));
   int data_fd = open(data_file.path().c_str(), O_RDWR, 000);
   EXPECT_GE(data_fd, 0);
@@ -281,14 +281,14 @@
   BlobFileWriter blob_file(data_fd, &data_file_size);
 
   // Merge the operations.
-  PayloadVersion version(kChromeOSMajorPayloadVersion,
+  PayloadVersion version(kBrilloMajorPayloadVersion,
                          kSourceMinorPayloadVersion);
   EXPECT_TRUE(ABGenerator::MergeOperations(
       &aops, version, 5, part_file.path(), &blob_file));
 
   // Check the result.
   InstallOperation_Type expected_op_type =
-      compressible ? InstallOperation::REPLACE_BZ : InstallOperation::REPLACE;
+      compressible ? InstallOperation::REPLACE_XZ : InstallOperation::REPLACE;
   EXPECT_EQ(1U, aops.size());
   InstallOperation new_op = aops[0].op;
   EXPECT_EQ(expected_op_type, new_op.type());
@@ -303,7 +303,7 @@
                              part_data.begin() + total_op_size);
   brillo::Blob expected_blob;
   if (compressible) {
-    ASSERT_TRUE(BzipCompress(expected_data, &expected_blob));
+    ASSERT_TRUE(XzCompress(expected_data, &expected_blob));
   } else {
     expected_blob = expected_data;
   }
@@ -384,19 +384,19 @@
 }
 
 TEST_F(ABGeneratorTest, SplitReplaceTest) {
-  TestSplitReplaceOrReplaceBzOperation(InstallOperation::REPLACE, false);
+  TestSplitReplaceOrReplaceXzOperation(InstallOperation::REPLACE, false);
 }
 
-TEST_F(ABGeneratorTest, SplitReplaceIntoReplaceBzTest) {
-  TestSplitReplaceOrReplaceBzOperation(InstallOperation::REPLACE, true);
+TEST_F(ABGeneratorTest, SplitReplaceIntoReplaceXzTest) {
+  TestSplitReplaceOrReplaceXzOperation(InstallOperation::REPLACE, true);
 }
 
-TEST_F(ABGeneratorTest, SplitReplaceBzTest) {
-  TestSplitReplaceOrReplaceBzOperation(InstallOperation::REPLACE_BZ, true);
+TEST_F(ABGeneratorTest, SplitReplaceXzTest) {
+  TestSplitReplaceOrReplaceXzOperation(InstallOperation::REPLACE_XZ, true);
 }
 
-TEST_F(ABGeneratorTest, SplitReplaceBzIntoReplaceTest) {
-  TestSplitReplaceOrReplaceBzOperation(InstallOperation::REPLACE_BZ, false);
+TEST_F(ABGeneratorTest, SplitReplaceXzIntoReplaceTest) {
+  TestSplitReplaceOrReplaceXzOperation(InstallOperation::REPLACE_XZ, false);
 }
 
 TEST_F(ABGeneratorTest, SortOperationsByDestinationTest) {
@@ -464,7 +464,7 @@
   aops.push_back(third_aop);
 
   BlobFileWriter blob_file(0, nullptr);
-  PayloadVersion version(kChromeOSMajorPayloadVersion,
+  PayloadVersion version(kBrilloMajorPayloadVersion,
                          kSourceMinorPayloadVersion);
   EXPECT_TRUE(ABGenerator::MergeOperations(&aops, version, 5, "", &blob_file));
 
@@ -484,19 +484,19 @@
 }
 
 TEST_F(ABGeneratorTest, MergeReplaceOperationsTest) {
-  TestMergeReplaceOrReplaceBzOperations(InstallOperation::REPLACE, false);
+  TestMergeReplaceOrReplaceXzOperations(InstallOperation::REPLACE, false);
 }
 
-TEST_F(ABGeneratorTest, MergeReplaceOperationsToReplaceBzTest) {
-  TestMergeReplaceOrReplaceBzOperations(InstallOperation::REPLACE, true);
+TEST_F(ABGeneratorTest, MergeReplaceOperationsToReplaceXzTest) {
+  TestMergeReplaceOrReplaceXzOperations(InstallOperation::REPLACE, true);
 }
 
-TEST_F(ABGeneratorTest, MergeReplaceBzOperationsTest) {
-  TestMergeReplaceOrReplaceBzOperations(InstallOperation::REPLACE_BZ, true);
+TEST_F(ABGeneratorTest, MergeReplaceXzOperationsTest) {
+  TestMergeReplaceOrReplaceXzOperations(InstallOperation::REPLACE_XZ, true);
 }
 
-TEST_F(ABGeneratorTest, MergeReplaceBzOperationsToReplaceTest) {
-  TestMergeReplaceOrReplaceBzOperations(InstallOperation::REPLACE_BZ, false);
+TEST_F(ABGeneratorTest, MergeReplaceXzOperationsToReplaceTest) {
+  TestMergeReplaceOrReplaceXzOperations(InstallOperation::REPLACE_XZ, false);
 }
 
 TEST_F(ABGeneratorTest, NoMergeOperationsTest) {
@@ -537,7 +537,7 @@
   aops.push_back(fourth_aop);
 
   BlobFileWriter blob_file(0, nullptr);
-  PayloadVersion version(kChromeOSMajorPayloadVersion,
+  PayloadVersion version(kBrilloMajorPayloadVersion,
                          kSourceMinorPayloadVersion);
   EXPECT_TRUE(ABGenerator::MergeOperations(&aops, version, 4, "", &blob_file));
 
diff --git a/payload_generator/delta_diff_utils_unittest.cc b/payload_generator/delta_diff_utils_unittest.cc
index e25c867..bc3dca5 100644
--- a/payload_generator/delta_diff_utils_unittest.cc
+++ b/payload_generator/delta_diff_utils_unittest.cc
@@ -136,7 +136,7 @@
   bool RunDeltaMovedAndZeroBlocks(ssize_t chunk_blocks,
                                   uint32_t minor_version) {
     BlobFileWriter blob_file(blob_fd_, &blob_size_);
-    PayloadVersion version(kChromeOSMajorPayloadVersion, minor_version);
+    PayloadVersion version(kBrilloMajorPayloadVersion, minor_version);
     ExtentRanges old_zero_blocks;
     return diff_utils::DeltaMovedAndZeroBlocks(&aops_,
                                                old_part_.path,
@@ -225,8 +225,7 @@
         new_extents,
         {},  // old_deflates
         {},  // new_deflates
-        PayloadVersion(kChromeOSMajorPayloadVersion,
-                       kSourceMinorPayloadVersion),
+        PayloadVersion(kBrilloMajorPayloadVersion, kSourceMinorPayloadVersion),
         &data,
         &op));
     EXPECT_FALSE(data.empty());
@@ -268,7 +267,7 @@
       new_extents,
       {},  // old_deflates
       {},  // new_deflates
-      PayloadVersion(kChromeOSMajorPayloadVersion, kSourceMinorPayloadVersion),
+      PayloadVersion(kBrilloMajorPayloadVersion, kSourceMinorPayloadVersion),
       &data,
       &op));
   EXPECT_TRUE(data.empty());
@@ -302,7 +301,7 @@
       new_extents,
       {},  // old_deflates
       {},  // new_deflates
-      PayloadVersion(kChromeOSMajorPayloadVersion, kSourceMinorPayloadVersion),
+      PayloadVersion(kBrilloMajorPayloadVersion, kSourceMinorPayloadVersion),
       &data,
       &op));
 
diff --git a/payload_generator/full_update_generator_unittest.cc b/payload_generator/full_update_generator_unittest.cc
index e398125..5f39e8b 100644
--- a/payload_generator/full_update_generator_unittest.cc
+++ b/payload_generator/full_update_generator_unittest.cc
@@ -90,7 +90,7 @@
     EXPECT_EQ(config_.hard_chunk_size / config_.block_size,
               aops[i].op.dst_extents(0).num_blocks());
     if (aops[i].op.type() != InstallOperation::REPLACE) {
-      EXPECT_EQ(InstallOperation::REPLACE_BZ, aops[i].op.type());
+      EXPECT_EQ(InstallOperation::REPLACE_XZ, aops[i].op.type());
     }
   }
 }
diff --git a/payload_generator/generate_delta_main.cc b/payload_generator/generate_delta_main.cc
index 16f360f..69ac8bb 100644
--- a/payload_generator/generate_delta_main.cc
+++ b/payload_generator/generate_delta_main.cc
@@ -509,16 +509,10 @@
   partition_names = base::SplitString(
       FLAGS_partition_names, ":", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
   CHECK(!partition_names.empty());
-  if (FLAGS_major_version == kChromeOSMajorPayloadVersion ||
-      FLAGS_new_partitions.empty()) {
-    LOG_IF(FATAL, partition_names.size() != 2)
-        << "To support more than 2 partitions, please use the "
-        << "--new_partitions flag and major version 2.";
-    LOG_IF(FATAL,
-           partition_names[0] != kPartitionNameRoot ||
-               partition_names[1] != kPartitionNameKernel)
-        << "To support non-default partition name, please use the "
-        << "--new_partitions flag and major version 2.";
+  if (FLAGS_major_version < kMinSupportedMajorPayloadVersion ||
+      FLAGS_major_version > kMaxSupportedMajorPayloadVersion) {
+    LOG(FATAL) << "Unsupported major version " << FLAGS_major_version;
+    return 1;
   }
 
   if (!FLAGS_new_partitions.empty()) {
@@ -577,8 +571,6 @@
   }
 
   if (!FLAGS_new_postinstall_config_file.empty()) {
-    LOG_IF(FATAL, FLAGS_major_version == kChromeOSMajorPayloadVersion)
-        << "Postinstall config is only allowed in major version 2 or newer.";
     brillo::KeyValueStore store;
     CHECK(store.Load(base::FilePath(FLAGS_new_postinstall_config_file)));
     CHECK(payload_config.target.LoadPostInstallConfig(store));
@@ -596,9 +588,6 @@
   CHECK(payload_config.target.LoadImageSize());
 
   if (!FLAGS_dynamic_partition_info_file.empty()) {
-    LOG_IF(FATAL, FLAGS_major_version == kChromeOSMajorPayloadVersion)
-        << "Dynamic partition info is only allowed in major version 2 or "
-           "newer.";
     brillo::KeyValueStore store;
     CHECK(store.Load(base::FilePath(FLAGS_dynamic_partition_info_file)));
     CHECK(payload_config.target.LoadDynamicPartitionMetadata(store));
diff --git a/payload_generator/payload_file.cc b/payload_generator/payload_file.cc
index 775a509..b55d03c 100644
--- a/payload_generator/payload_file.cc
+++ b/payload_generator/payload_file.cc
@@ -74,11 +74,9 @@
   manifest_.set_block_size(config.block_size);
   manifest_.set_max_timestamp(config.max_timestamp);
 
-  if (major_version_ == kBrilloMajorPayloadVersion) {
-    if (config.target.dynamic_partition_metadata != nullptr)
-      *(manifest_.mutable_dynamic_partition_metadata()) =
-          *(config.target.dynamic_partition_metadata);
-  }
+  if (config.target.dynamic_partition_metadata != nullptr)
+    *(manifest_.mutable_dynamic_partition_metadata()) =
+        *(config.target.dynamic_partition_metadata);
 
   return true;
 }
@@ -86,13 +84,6 @@
 bool PayloadFile::AddPartition(const PartitionConfig& old_conf,
                                const PartitionConfig& new_conf,
                                const vector<AnnotatedOperation>& aops) {
-  // Check partitions order for Chrome OS
-  if (major_version_ == kChromeOSMajorPayloadVersion) {
-    const vector<const char*> part_order = {kPartitionNameRoot,
-                                            kPartitionNameKernel};
-    TEST_AND_RETURN_FALSE(part_vec_.size() < part_order.size());
-    TEST_AND_RETURN_FALSE(new_conf.name == part_order[part_vec_.size()]);
-  }
   Partition part;
   part.name = new_conf.name;
   part.aops = aops;
@@ -134,66 +125,45 @@
   }
 
   // Copy the operations and partition info from the part_vec_ to the manifest.
-  manifest_.clear_install_operations();
-  manifest_.clear_kernel_install_operations();
   manifest_.clear_partitions();
   for (const auto& part : part_vec_) {
-    if (major_version_ == kBrilloMajorPayloadVersion) {
-      PartitionUpdate* partition = manifest_.add_partitions();
-      partition->set_partition_name(part.name);
-      if (part.postinstall.run) {
-        partition->set_run_postinstall(true);
-        if (!part.postinstall.path.empty())
-          partition->set_postinstall_path(part.postinstall.path);
-        if (!part.postinstall.filesystem_type.empty())
-          partition->set_filesystem_type(part.postinstall.filesystem_type);
-        partition->set_postinstall_optional(part.postinstall.optional);
+    PartitionUpdate* partition = manifest_.add_partitions();
+    partition->set_partition_name(part.name);
+    if (part.postinstall.run) {
+      partition->set_run_postinstall(true);
+      if (!part.postinstall.path.empty())
+        partition->set_postinstall_path(part.postinstall.path);
+      if (!part.postinstall.filesystem_type.empty())
+        partition->set_filesystem_type(part.postinstall.filesystem_type);
+      partition->set_postinstall_optional(part.postinstall.optional);
+    }
+    if (!part.verity.IsEmpty()) {
+      if (part.verity.hash_tree_extent.num_blocks() != 0) {
+        *partition->mutable_hash_tree_data_extent() =
+            part.verity.hash_tree_data_extent;
+        *partition->mutable_hash_tree_extent() = part.verity.hash_tree_extent;
+        partition->set_hash_tree_algorithm(part.verity.hash_tree_algorithm);
+        if (!part.verity.hash_tree_salt.empty())
+          partition->set_hash_tree_salt(part.verity.hash_tree_salt.data(),
+                                        part.verity.hash_tree_salt.size());
       }
-      if (!part.verity.IsEmpty()) {
-        if (part.verity.hash_tree_extent.num_blocks() != 0) {
-          *partition->mutable_hash_tree_data_extent() =
-              part.verity.hash_tree_data_extent;
-          *partition->mutable_hash_tree_extent() = part.verity.hash_tree_extent;
-          partition->set_hash_tree_algorithm(part.verity.hash_tree_algorithm);
-          if (!part.verity.hash_tree_salt.empty())
-            partition->set_hash_tree_salt(part.verity.hash_tree_salt.data(),
-                                          part.verity.hash_tree_salt.size());
-        }
-        if (part.verity.fec_extent.num_blocks() != 0) {
-          *partition->mutable_fec_data_extent() = part.verity.fec_data_extent;
-          *partition->mutable_fec_extent() = part.verity.fec_extent;
-          partition->set_fec_roots(part.verity.fec_roots);
-        }
-      }
-      for (const AnnotatedOperation& aop : part.aops) {
-        *partition->add_operations() = aop.op;
-      }
-      if (part.old_info.has_size() || part.old_info.has_hash())
-        *(partition->mutable_old_partition_info()) = part.old_info;
-      if (part.new_info.has_size() || part.new_info.has_hash())
-        *(partition->mutable_new_partition_info()) = part.new_info;
-    } else {
-      // major_version_ == kChromeOSMajorPayloadVersion
-      if (part.name == kPartitionNameKernel) {
-        for (const AnnotatedOperation& aop : part.aops)
-          *manifest_.add_kernel_install_operations() = aop.op;
-        if (part.old_info.has_size() || part.old_info.has_hash())
-          *manifest_.mutable_old_kernel_info() = part.old_info;
-        if (part.new_info.has_size() || part.new_info.has_hash())
-          *manifest_.mutable_new_kernel_info() = part.new_info;
-      } else {
-        for (const AnnotatedOperation& aop : part.aops)
-          *manifest_.add_install_operations() = aop.op;
-        if (part.old_info.has_size() || part.old_info.has_hash())
-          *manifest_.mutable_old_rootfs_info() = part.old_info;
-        if (part.new_info.has_size() || part.new_info.has_hash())
-          *manifest_.mutable_new_rootfs_info() = part.new_info;
+      if (part.verity.fec_extent.num_blocks() != 0) {
+        *partition->mutable_fec_data_extent() = part.verity.fec_data_extent;
+        *partition->mutable_fec_extent() = part.verity.fec_extent;
+        partition->set_fec_roots(part.verity.fec_roots);
       }
     }
+    for (const AnnotatedOperation& aop : part.aops) {
+      *partition->add_operations() = aop.op;
+    }
+    if (part.old_info.has_size() || part.old_info.has_hash())
+      *(partition->mutable_old_partition_info()) = part.old_info;
+    if (part.new_info.has_size() || part.new_info.has_hash())
+      *(partition->mutable_new_partition_info()) = part.new_info;
   }
 
   // Signatures appear at the end of the blobs. Note the offset in the
-  // manifest_.
+  // |manifest_|.
   uint64_t signature_blob_length = 0;
   if (!private_key_path.empty()) {
     TEST_AND_RETURN_FALSE(PayloadSigner::SignatureBlobLength(
@@ -201,7 +171,6 @@
     PayloadSigner::AddSignatureToManifest(
         next_blob_offset,
         signature_blob_length,
-        major_version_ == kChromeOSMajorPayloadVersion,
         &manifest_);
   }
 
@@ -229,18 +198,14 @@
   TEST_AND_RETURN_FALSE(
       WriteUint64AsBigEndian(&writer, serialized_manifest.size()));
 
-  // Write metadata signature size.
-  uint32_t metadata_signature_size = 0;
-  if (major_version_ == kBrilloMajorPayloadVersion) {
-    // Metadata signature has the same size as payload signature, because they
-    // are both the same kind of signature for the same kind of hash.
-    uint32_t metadata_signature_size = htobe32(signature_blob_length);
-    TEST_AND_RETURN_FALSE_ERRNO(writer.Write(&metadata_signature_size,
-                                             sizeof(metadata_signature_size)));
-    metadata_size += sizeof(metadata_signature_size);
-    // Set correct size instead of big endian size.
-    metadata_signature_size = signature_blob_length;
-  }
+  // Metadata signature has the same size as payload signature, because they
+  // are both the same kind of signature for the same kind of hash.
+  uint32_t metadata_signature_size = htobe32(signature_blob_length);
+  TEST_AND_RETURN_FALSE_ERRNO(
+      writer.Write(&metadata_signature_size, sizeof(metadata_signature_size)));
+  metadata_size += sizeof(metadata_signature_size);
+  // Set correct size instead of big endian size.
+  metadata_signature_size = signature_blob_length;
 
   // Write protobuf
   LOG(INFO) << "Writing final delta file protobuf... "
@@ -249,8 +214,7 @@
       writer.Write(serialized_manifest.data(), serialized_manifest.size()));
 
   // Write metadata signature blob.
-  if (major_version_ == kBrilloMajorPayloadVersion &&
-      !private_key_path.empty()) {
+  if (!private_key_path.empty()) {
     brillo::Blob metadata_hash, metadata_signature;
     TEST_AND_RETURN_FALSE(HashCalculator::RawHashOfFile(
         payload_file, metadata_size, &metadata_hash));
@@ -262,7 +226,7 @@
         writer.Write(metadata_signature.data(), metadata_signature.size()));
   }
 
-  // Append the data blobs
+  // Append the data blobs.
   LOG(INFO) << "Writing final delta file data blobs...";
   int blobs_fd = open(ordered_blobs_path.c_str(), O_RDONLY, 0);
   ScopedFdCloser blobs_fd_closer(&blobs_fd);
diff --git a/payload_generator/payload_generation_config.cc b/payload_generator/payload_generation_config.cc
index 3b791c8..e1f700a 100644
--- a/payload_generator/payload_generation_config.cc
+++ b/payload_generator/payload_generation_config.cc
@@ -219,8 +219,7 @@
 }
 
 bool PayloadVersion::Validate() const {
-  TEST_AND_RETURN_FALSE(major == kChromeOSMajorPayloadVersion ||
-                        major == kBrilloMajorPayloadVersion);
+  TEST_AND_RETURN_FALSE(major == kBrilloMajorPayloadVersion);
   TEST_AND_RETURN_FALSE(minor == kFullPayloadMinorVersion ||
                         minor == kSourceMinorPayloadVersion ||
                         minor == kOpSrcHashMinorPayloadVersion ||
@@ -236,13 +235,10 @@
     case InstallOperation::REPLACE:
     case InstallOperation::REPLACE_BZ:
       // These operations were included in the original payload format.
-      return true;
-
     case InstallOperation::REPLACE_XZ:
-      // These operations are included in the major version used in Brillo, but
-      // can also be used with minor version 3 or newer.
-      return major == kBrilloMajorPayloadVersion ||
-             minor >= kOpSrcHashMinorPayloadVersion;
+      // These operations are included minor version 3 or newer and full
+      // payloads.
+      return true;
 
     case InstallOperation::ZERO:
     case InstallOperation::DISCARD:
@@ -298,8 +294,6 @@
   for (const PartitionConfig& part : target.partitions) {
     TEST_AND_RETURN_FALSE(part.ValidateExists());
     TEST_AND_RETURN_FALSE(part.size % block_size == 0);
-    if (version.major == kChromeOSMajorPayloadVersion)
-      TEST_AND_RETURN_FALSE(part.postinstall.IsEmpty());
     if (version.minor < kVerityMinorPayloadVersion)
       TEST_AND_RETURN_FALSE(part.verity.IsEmpty());
   }
diff --git a/payload_generator/payload_properties.cc b/payload_generator/payload_properties.cc
index 53e69f3..bc82eb7 100644
--- a/payload_generator/payload_properties.cc
+++ b/payload_generator/payload_properties.cc
@@ -119,8 +119,7 @@
     metadata_signatures_ = base::JoinString(base64_signatures, ":");
   }
 
-  is_delta_ = manifest.has_old_image_info() || manifest.has_old_kernel_info() ||
-              manifest.has_old_rootfs_info() ||
+  is_delta_ = manifest.has_old_image_info() ||
               std::any_of(manifest.partitions().begin(),
                           manifest.partitions().end(),
                           [](const PartitionUpdate& part) {
diff --git a/payload_generator/payload_signer.cc b/payload_generator/payload_signer.cc
index 2a7021f..420329f 100644
--- a/payload_generator/payload_signer.cc
+++ b/payload_generator/payload_signer.cc
@@ -98,23 +98,20 @@
   uint64_t metadata_size = payload_metadata.GetMetadataSize();
   uint32_t metadata_signature_size =
       payload_metadata.GetMetadataSignatureSize();
-  if (payload_metadata.GetMajorVersion() == kBrilloMajorPayloadVersion) {
-    // Write metadata signature size in header.
-    uint32_t metadata_signature_size_be =
-        htobe32(metadata_signature_blob.size());
-    memcpy(payload.data() + manifest_offset,
-           &metadata_signature_size_be,
-           sizeof(metadata_signature_size_be));
-    manifest_offset += sizeof(metadata_signature_size_be);
-    // Replace metadata signature.
-    payload.erase(payload.begin() + metadata_size,
-                  payload.begin() + metadata_size + metadata_signature_size);
-    payload.insert(payload.begin() + metadata_size,
-                   metadata_signature_blob.begin(),
-                   metadata_signature_blob.end());
-    metadata_signature_size = metadata_signature_blob.size();
-    LOG(INFO) << "Metadata signature size: " << metadata_signature_size;
-  }
+  // Write metadata signature size in header.
+  uint32_t metadata_signature_size_be = htobe32(metadata_signature_blob.size());
+  memcpy(payload.data() + manifest_offset,
+         &metadata_signature_size_be,
+         sizeof(metadata_signature_size_be));
+  manifest_offset += sizeof(metadata_signature_size_be);
+  // Replace metadata signature.
+  payload.erase(payload.begin() + metadata_size,
+                payload.begin() + metadata_size + metadata_signature_size);
+  payload.insert(payload.begin() + metadata_size,
+                 metadata_signature_blob.begin(),
+                 metadata_signature_blob.end());
+  metadata_signature_size = metadata_signature_blob.size();
+  LOG(INFO) << "Metadata signature size: " << metadata_signature_size;
 
   DeltaArchiveManifest manifest;
   TEST_AND_RETURN_FALSE(payload_metadata.GetManifest(payload, &manifest));
@@ -138,7 +135,6 @@
     PayloadSigner::AddSignatureToManifest(
         payload.size() - metadata_size - metadata_signature_size,
         signature_blob.size(),
-        payload_metadata.GetMajorVersion() == kChromeOSMajorPayloadVersion,
         &manifest);
 
     // Updates the payload to include the new manifest.
@@ -209,25 +205,12 @@
 
 void PayloadSigner::AddSignatureToManifest(uint64_t signature_blob_offset,
                                            uint64_t signature_blob_length,
-                                           bool add_dummy_op,
                                            DeltaArchiveManifest* manifest) {
   LOG(INFO) << "Making room for signature in file";
   manifest->set_signatures_offset(signature_blob_offset);
   LOG(INFO) << "set? " << manifest->has_signatures_offset();
   manifest->set_signatures_offset(signature_blob_offset);
   manifest->set_signatures_size(signature_blob_length);
-  // Add a dummy op at the end to appease older clients
-  if (add_dummy_op) {
-    InstallOperation* dummy_op = manifest->add_kernel_install_operations();
-    dummy_op->set_type(InstallOperation::REPLACE);
-    dummy_op->set_data_offset(signature_blob_offset);
-    dummy_op->set_data_length(signature_blob_length);
-    Extent* dummy_extent = dummy_op->add_dst_extents();
-    // Tell the dummy op to write this data to a big sparse hole
-    dummy_extent->set_start_block(kSparseHole);
-    dummy_extent->set_num_blocks(
-        utils::DivRoundUp(signature_blob_length, kBlockSize));
-  }
 }
 
 bool PayloadSigner::VerifySignedPayload(const string& payload_path,
diff --git a/payload_generator/payload_signer.h b/payload_generator/payload_signer.h
index 83ddadc..71f4983 100644
--- a/payload_generator/payload_signer.h
+++ b/payload_generator/payload_signer.h
@@ -39,12 +39,9 @@
   static bool VerifySignedPayload(const std::string& payload_path,
                                   const std::string& public_key_path);
 
-  // Adds specified signature offset/length to given |manifest|, also adds a
-  // dummy operation that points to a signature blob located at the specified
-  // offset/length if |add_dummy_op| is true.
+  // Adds specified signature offset/length to given |manifest|.
   static void AddSignatureToManifest(uint64_t signature_blob_offset,
                                      uint64_t signature_blob_length,
-                                     bool add_dummy_op,
                                      DeltaArchiveManifest* manifest);
 
   // Given a raw |hash| and a private key in |private_key_path| calculates the