编译版本，做OTA升级包，报莫名其妙的错误，经检查（命令：df  -h）是服务器硬盘空间缩小到1.8G以下导致，通过删除不需要的log文件以及多余的垃圾文件即可解决该问题。

Could not append verity metadata!: Invalid sparse file format at data block at 49529368
error: file_write: incomplete write
Failed to write sparse file
Traceback (most recent call last):
  File "./build/tools/releasetools/add_img_to_target_files", line 362, in <module>
    main(sys.argv[1:])
  File "./build/tools/releasetools/add_img_to_target_files", line 356, in main
    AddImagesToTargetFiles(args[0])
  File "./build/tools/releasetools/add_img_to_target_files", line 322, in AddImagesToTargetFiles
    AddSystem(output_zip, recovery_img=recovery_image, boot_img=boot_image)
  File "./build/tools/releasetools/add_img_to_target_files", line 65, in AddSystem
    block_list=block_list)
  File "./build/tools/releasetools/add_img_to_target_files", line 80, in BuildSystem
    return CreateImage(input_dir, info_dict, "system", block_list=block_list)
  File "./build/tools/releasetools/add_img_to_target_files", line 171, in CreateImage
    assert succ, "build " + what + ".img image failed"
AssertionError: build system.img image failed