如果要检查Hadoop中存在哪些压缩器本机库，可以使用checknative -a命令来执行。

$ hadoop checknative -a

18/03/16 19:47:24 INFO bzip2.Bzip2Factory: Successfully loaded & initialized native-bzip2 library system-native
18/03/16 19:47:24 INFO zlib.ZlibFactory: Successfully loaded & initialized native-zlib library
Native library checking:
hadoop:  true /usr/hadoop/hadoop-2.9.0/lib/native/libhadoop.so.1.0.0
zlib:    true /lib/x86_64-linux-gnu/libz.so.1
snappy:  true /usr/lib/x86_64-linux-gnu/libsnappy.so.1
zstd  :  false 
lz4:     true revision:10301
bzip2:   true /lib/x86_64-linux-gnu/libbz2.so.1
openssl: false Cannot load libcrypto.so (libcrypto.so: cannot open shared object file: No such file or directory)!
18/03/16 19:47:24 INFO util.ExitUtil: Exiting with status 1: ExitException

如我们所见，使用checknative命令可以检查hadoop中存在哪些本机库。对于zlib，snappy，lz4和bzip2，它为true，对于zstd为false。我们还可以查看Hadoop的本机库。