[erlang-questions] How about make the erl to be relocatable ? for multiple erlang versions installed on a same host

[Attila Rajmund Nohl]

Hello!

I'm not sure if I totally understand your problem, but I see two solutions:
1, use kerl (https://github.com/kerl/kerl) to manage your
installations. Download, build and install all required Erlang
versions, then simply activate the one you need to use.
2, create a Docker image for each required Erlang version and install
your software inside that image (possibly using bind mount).

2017-06-06 4:38 GMT+02:00 derek <denc716@REDACTED>:
>
> the default erl is a shell script, like this:
>
> #!/bin/sh
> [...]
> # %CopyrightEnd%
> #
> ROOTDIR="/usr/lib/erlang"
> ...
>
>
> Where the ROOTDIR is set to a hard code string at installation time, and it
> makes the erl script not relocatable,
>
> sometimes we want to install multiple erlang versions for testing features,
> like this following is my way to test install esl packaged erlang-20.0-rc2,
> all just extract "install" to my $HOME/opt/... without sysadmin permission:
>
> # download the deb or rpm package
> $ wget -P ./Downloads -m
> https://packages.erlang-solutions.com/erlang/esl-erlang/FLAVOUR_1_general/esl-erlang_20.0-rc2-1~debian~jessie_amd64.deb
>
> # the deb is an ar format, you can use standard ar/tar tools to extract to
> local ./usr/lib/erlang/
> $ ar p
> ./Downloads/packages.erlang-solutions.com/erlang/esl-erlang/FLAVOUR_1_general/esl-erlang_20.0-rc2-1~debian~jessie_amd64.deb
> data.tar.xz | tar --xz -xvv ./usr/lib/erlang/
>
> # or to extract the rpm, it is cpio format:
> # rpm2cpio
> ./Downloads/packages.erlang-solutions.com/erlang/esl-erlang/FLAVOUR_1_general/esl-erlang_20.0-rc2-1~centos~6_amd64.rpm
> | cpio -vid './usr/lib/erlang/*'
>
> Once I get ./usr/lib/erlang/ I usually renamed to ./opt/ ...
>
> $ mv -v ./usr/lib/erlang/ ./opt/esl-erlang_20.0-rc2-1~debian~jessie
>
> Then a problem is this erl doesn't run, because it tries to access the hard
> coded ROOTDIR from /usr/lib/erlang (does not exist)
>
> (the "bash -xe" is only to show how does the shell script run, but not
> necessary)
>
> $ bash -xe ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl
> + ROOTDIR=/usr/lib/erlang
> + BINDIR=/usr/lib/erlang/erts-9.0/bin
> + EMU=beam
> ++ echo ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl
> ++ sed 's/.*\///'
> + PROGNAME=erl
> + export EMU
> + export ROOTDIR
> + export BINDIR
> + export PROGNAME
> + exec /usr/lib/erlang/erts-9.0/bin/erlexec
> ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl: line 29:
> /usr/lib/erlang/erts-9.0/bin/erlexec: No such file or directory
>
> So I back it up and make little changes to make it read path from where it's
> installed:
>
> $ \cp -va ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl{,.orig}
> `./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl' ->
> `./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl.orig'
>
> $ vim ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl
>
> Diff is here:
>
> $ diff -u ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl{.orig,}
> --- ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl.orig 2017-06-06
> 01:57:50.796140791 +0000
> +++ ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl 2017-06-06
> 01:59:15.713988348 +0000
> @@ -18,10 +18,12 @@
>  #
>  # %CopyrightEnd%
>  #
> -ROOTDIR="/usr/lib/erlang"
> +# ROOTDIR="/usr/lib/erlang"
> +ROOTDIR="$(readlink -f ${0%/*}/..)"
>  BINDIR=$ROOTDIR/erts-9.0/bin
>  EMU=beam
> -PROGNAME=`echo $0 | sed 's/.*\///'`
> +# PROGNAME=`echo $0 | sed 's/.*\///'`
> +PROGNAME="${0##*/}"
>  export EMU
>  export ROOTDIR
>  export BINDIR
>
> Then it runs:
>
> $ bash -xe ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl
> ++ readlink -f ./opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/..
> + ROOTDIR=/home/username/opt/esl-erlang_20.0-rc2-1~debian~jessie
> + BINDIR=/home/username/opt/esl-erlang_20.0-rc2-1~debian~jessie/erts-9.0/bin
> + EMU=beam
> + PROGNAME=erl
> + export EMU
> + export ROOTDIR
> + export BINDIR
> + export PROGNAME
> + exec
> /home/username/opt/esl-erlang_20.0-rc2-1~debian~jessie/erts-9.0/bin/erlexec
> Erlang/OTP 20 [RELEASE CANDIDATE 2] [erts-9.0] [source] [64-bit] [smp:24:24]
> [ds:24:24:10] [async-threads:10] [hipe] [kernel-poll:false]
>
> Eshell V9.0  (abort with ^G)
> 1>
>
> I am aware of there is a "Install" script can be used to install itself to
> another location, but the problem remains: it's still hard coded of new
> install path:
> ./opt/esl-erlang_20.0-rc2-1~debian~jessie/Install
>
>
> The problem need to be solved, especially when used with docker's bind mount
> feature, it can be mounted to a complete different path, I hope the erl can
> still run without any change:
>
> Here it shows my changed erl escript can still run when bind mounted to the
> container's "/opt/esl-erlang_20.0-rc2-1~debian~jessie"
>
> $ docker run -it --rm -v $PWD/opt:/opt:ro ubuntu bash -xe
> /opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/erl
> ++ readlink -f /opt/esl-erlang_20.0-rc2-1~debian~jessie/bin/..
> + ROOTDIR=/opt/esl-erlang_20.0-rc2-1~debian~jessie
> + BINDIR=/opt/esl-erlang_20.0-rc2-1~debian~jessie/erts-9.0/bin
> + EMU=beam
> + PROGNAME=erl
> + export EMU
> + export ROOTDIR
> + export BINDIR
> + export PROGNAME
> + exec /opt/esl-erlang_20.0-rc2-1~debian~jessie/erts-9.0/bin/erlexec
> Erlang/OTP 20 [RELEASE CANDIDATE 2] [erts-9.0] [source] [64-bit] [smp:24:24]
> [ds:24:24:10] [async-threads:10] [hipe] [kernel-poll:false]
>
> Eshell V9.0  (abort with ^G)
> 1>
> User switch command
>  --> q
>
> Or add to PATH:
>
> $ docker run -it --rm -v $PWD/opt:/opt:ro -e
> PATH=/opt/esl-erlang_20.0-rc2-1~debian~jessie/bin:$PATH -e LANG=C.UTF-8
> ubuntu erl +pc unicode
> Erlang/OTP 20 [RELEASE CANDIDATE 2] [erts-9.0] [source] [64-bit] [smp:24:24]
> [ds:24:24:10] [async-threads:10] [hipe] [kernel-poll:false]
>
> Eshell V9.0  (abort with ^G)
> 1> io:format("~tp~n", [{'hello_юникод_世界', <<"Hello, 世界; юникод"/utf8>>,
> "Hello, 世界; юникод"}]).
> {'hello_юникод_世界',<<"Hello, 世界; юникод"/utf8>>,"Hello, 世界; юникод"}
> ok
> 2>
> User switch command
>  --> q
>
>
> Hopefully this entertains; I can make a PR to  https://github.com/erlang/otp
> if somebody like.
>
>
>
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