如果在通过ssh连接到远程主机时发生此问题，则可能是远程系统缺少某些区域设置。我不打算重复如何安装和配置区域设置，因为其他答案已经很好地解释了这一点。

正如其他答案所指出的，ssh应该将本地计算机的区域设置传递给远程主机。例如，如果你设置了澳大利亚地区(例如en_AU.UFT-8)，并且你正在连接到一个新设置的Ubuntu服务器，它只提供en_US。UTF-8，那么您将收到此警告。

要解决这个问题，你有几个选择:

在远程主机上安装所需的区域设置，使它们与客户端上配置的区域设置匹配。 将SSH配置更改为不传递客户端环境变量。我不建议这样做。 通过从.bashrc文件和朋友导出语言环境设置来覆盖远程机器上的语言环境。

在我的例子中，这是输出:

LANGUAGE = (unset),
LC_ALL = (unset),
LC_PAPER = "ro_RO.UTF-8",
LC_ADDRESS = "ro_RO.UTF-8",
....

解决方案是:

sudo locale-gen ro_RO.UTF-8

我现在使用这个:

$ cat /etc/environment
...
LC_ALL=en_US.UTF-8
LANG=en_US.UTF-8

然后注销SSH会话，重新登录。

旧的回答:

只有这一点对我有帮助:

$ locale
locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE=en_US.UTF-8
LC_NUMERIC=ru_RU.UTF-8
LC_TIME=ru_RU.UTF-8
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=ru_RU.UTF-8
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=ru_RU.UTF-8
LC_NAME=ru_RU.UTF-8
LC_ADDRESS=ru_RU.UTF-8
LC_TELEPHONE=ru_RU.UTF-8
LC_MEASUREMENT=ru_RU.UTF-8
LC_IDENTIFICATION=ru_RU.UTF-8
LC_ALL=

$ sudo su

# export LANGUAGE=en_US.UTF-8
# export LANG=en_US.UTF-8
# export LC_ALL=en_US.UTF-8

# locale-gen en_US.UTF-8
Generating locales...
  en_US.UTF-8... up-to-date
Generation complete.

# dpkg-reconfigure locales
Generating locales...
  en_AG.UTF-8... done
  en_AU.UTF-8... done
  en_BW.UTF-8... done
  en_CA.UTF-8... done
  en_DK.UTF-8... done
  en_GB.UTF-8... done
  en_HK.UTF-8... done
  en_IE.UTF-8... done
  en_IN.UTF-8... done
  en_NG.UTF-8... done
  en_NZ.UTF-8... done
  en_PH.UTF-8... done
  en_SG.UTF-8... done
  en_US.UTF-8... up-to-date
  en_ZA.UTF-8... done
  en_ZM.UTF-8... done
  en_ZW.UTF-8... done
Generation complete.

# exit

$ locale
LANG=en_US.UTF-8
LANGUAGE=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=en_US.UTF-8

我在/etc/locale.conf上设置了LC_COLLATE=C。我简单地删除了这一行，因此只有LANG=en_US。设置了UTF-8(或等效的UTF-8)，就不会再有问题了。

将LC_TYPE环境变量设置为默认的区域语言“C”将有助于消除此警告。

执行export LC_CTYPE="C"，然后尝试执行perl命令。

附注:您需要在/etc/environment文件或/etc/default/locale文件中设置此变量以获得永久解决方案。

每当我在最新的Kali Linux版本上运行Perl脚本(比如enum4linux)时，都会遇到这个问题。

kali@kali:~$ lsb_release -a
No LSB modules are available.
Distributor ID:    Kali
Description:    Kali GNU/Linux Rolling
Release:    2020.3
Codename:    kali-rolling
kali@kali:~$

例如,

kali@kali:~$ enum4linux
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
    LANGUAGE = (unset),
    LC_ALL = (unset),
    LC_ADDRESS = "ms_MY.UTF-8",
    LC_NAME = "ms_MY.UTF-8",
    LC_MONETARY = "ms_MY.UTF-8",
    LC_PAPER = "ms_MY.UTF-8",
    LC_IDENTIFICATION = "ms_MY.UTF-8",
    LC_TELEPHONE = "ms_MY.UTF-8",
    LC_MEASUREMENT = "ms_MY.UTF-8",
    LC_TIME = "ms_MY.UTF-8",
    LC_NUMERIC = "ms_MY.UTF-8",
    LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
enum4linux v0.8.9 (http://labs.portcullis.co.uk/application/enum4linux/)
Copyright (C) 2011 Mark Lowe (mrl@portcullis-security.com)

请看给出的警告信息。

perl: warning: Falling back to a fallback locale ("en_US.UTF-8").

另外，注意LC_ALL = (unset)

解决办法很简单。你所要做的就是设置它。

export LC_ALL=en_US.UTF-8

例如,

kali@kali:~$ export LC_ALL=en_US.UTF-8
kali@kali:~$

问题解决了

kali@kali:~$ enum4linux
enum4linux v0.8.9 (http://labs.portcullis.co.uk/application/enum4linux/)
Copyright (C) 2011 Mark Lowe (mrl@portcullis-security.com)

对于永久解决方案，您可能希望将其添加到.bashrc文件中。