最近刚把RK3399的Ubuntu系统跑起来，当作云计算服务器使用。
当我在电脑使用SSH访问它时，出现以下情况：

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = (unset),
        LC_ALL = (unset),
        LC_TIME = "zh_CN.UTF-8",
        LC_MONETARY = "zh_CN.UTF-8",
        LC_ADDRESS = "zh_CN.UTF-8",
        LC_TELEPHONE = "zh_CN.UTF-8",
        LC_NAME = "zh_CN.UTF-8",
        LC_MEASUREMENT = "zh_CN.UTF-8",
        LC_IDENTIFICATION = "zh_CN.UTF-8",
        LC_NUMERIC = "zh_CN.UTF-8",
        LC_PAPER = "zh_CN.UTF-8",
        LANG = "C.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("C.UTF-8").

问题定位

在firefly中执行

$ locale -a
C
C.UTF-8
POSIX

执行以下命令

$ sudo apt-get install language-pack-zh-hans
$ sudo apt-get install language-pack-en

$ locale -a

C
C.UTF-8
POSIX
en_AG
en_AG.utf8
en_AU.utf8
en_BW.utf8
en_CA.utf8
en_DK.utf8
en_GB.utf8
en_HK.utf8
en_IE.utf8
en_IL
en_IL.utf8
en_IN
en_IN.utf8
en_NG
en_NG.utf8
en_NZ.utf8
en_PH.utf8
en_SG.utf8
en_US.utf8
en_ZA.utf8
en_ZM
en_ZM.utf8
en_ZW.utf8
zh_CN.utf8
zh_SG.utf8

至此，这个问题已解决。