> > Just curious, does that mean that in "normal terminals" (not docker) it
> uses `FRAME_TERMINAL_CODING (f)
> > ` but in docker it uses `safe_terminal_coding`?
>
> Looks like that, yes.  It would mean that the docker doesn't define a
> locale environment which defines a usable codeset.  I know nothing
> about dockers, so I have no idea how could this happen.
>

Okay, for information here is the env and locale inside docker containers:

```
silex@silex-laptop:~$ docker run -it --rm silex/emacs:master env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=b1366c3c8820
TERM=xterm
EMACS_BRANCH=master
EMACS_VERSION=master
HOME=/root

silex@silex-laptop:~$ docker run -it --rm silex/emacs:master locale
LANG=
LANGUAGE=
LC_CTYPE="POSIX"
LC_NUMERIC="POSIX"
LC_TIME="POSIX"
LC_COLLATE="POSIX"
LC_MONETARY="POSIX"
LC_MESSAGES="POSIX"
LC_PAPER="POSIX"
LC_NAME="POSIX"
LC_ADDRESS="POSIX"
LC_TELEPHONE="POSIX"
LC_MEASUREMENT="POSIX"
LC_IDENTIFICATION="POSIX"
LC_ALL=
```

Out of curiosity I might investigate why this happens, but maybe there lies
some unharmful bug in emacs there that went unnoticed for long because
`safe_terminal_coding` just works.

Is all the detection happening in `setup_coding_system`? I maybe modify
Emacs' source so it reports what is being detected and it might give us
clues about what differs in the docker container.

I suspect the same problem happens in LXC containers.

Regards,
Philippe