enable user-defined extended attributes for ext3 file systems; 增加ext3 文件系统的扩展属性；

To enable user-defined extended attributes for ext3 file systems (i.e. device), use:

tune2fs -o user_xattr /dev/device

Alternatively, extended attributes for a file system can be enabled at mount time, as in:

mount /dev/device /path/to/cache -o user_xattr

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