报错信息如下：

# tar -zxvf extmail-1.2.tar.gz

tar: This does not look like a tar archive

tar: Skipping to next header

tar: Exiting with failure status due to previous errors

解决：

# file extmail-1.2.tar.gz

extmail-1.2.tar.gz: gzip compressed data, from Unix

# gzip -d extmail-1.2.tar.gz

# tar -xf extmail-1.2.tar