Error when compiling ocaml-base-compiler: bwrap can't mkdir .ccache

[tholop]

I installed Opam 2.0.4 on my Ubuntu 16.04 and want to create a first switch. However, it fails because bwrap is not able to create a .ccache directory even though this folder exists (I checked). The error is bwrap: Can't mkdir parents for /home/tholop/.ccache: No such file or directory. The detailed output is:

tholop@demeter:~$ opam switch create 4.05.0

<><> Gathering sources ><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ocaml-base-compiler.4.05.0] downloaded from https://github.com/ocaml/ocaml/archive/4.05.0.tar.gz

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ERROR] The compilation of ocaml-base-compiler failed at
        "/share/tholop/.opam/opam-init/hooks/sandbox.sh build ./configure -prefix
        /share/tholop/.opam/4.05.0 -with-debug-runtime".
∗ installed base-bigarray.base
∗ installed base-threads.base
∗ installed base-unix.base

#=== ERROR while compiling ocaml-base-compiler.4.05.0 =========================#
# context     2.0.4 | linux/x86_64 |  | https://opam.ocaml.org#1ae42aaa
# path        /share/tholop/.opam/4.05.0/.opam-switch/build/ocaml-base-compiler.4.05.0
# command     /share/tholop/.opam/opam-init/hooks/sandbox.sh build ./configure -prefix /share/tholop/.opam/4.05.0 -with-debug-runtime
# exit-code   1
# env-file    /share/tholop/.opam/log/ocaml-base-compiler-150540-865888.env
# output-file /share/tholop/.opam/log/ocaml-base-compiler-150540-865888.out
### output ###
# bwrap: Can't mkdir parents for /home/tholop/.ccache: No such file or directory



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
┌─ The following actions failed
│ λ build ocaml-base-compiler 4.05.0
└─ 
┌─ The following changes have been performed (the rest was aborted)
│ ∗ install base-bigarray base
│ ∗ install base-threads  base
│ ∗ install base-unix     base
└─ 
# Run eval $(opam env) to update the current shell environment
Switch initialisation failed: clean up? ('n' will leave the switch partially installed) [Y/n] y

Such an issue has already been mentioned by @abhcs in #3424 (comment).

The bwrap I am using is version 0.3.1 and was installed from the avsm PPA. I tried to install it manually and to test different versions, without success. I also tried to init opam with --disable-sandboxing. It doesn't work.

Please, would you have any idea how to solve this problem? Thank you.

[tholop]

Actually, I did not reinitialize my Opam properly. It is solved now.

The solution was:
rm -rf .opam/ and then opam init --comp=4.05.0 --disable-sandboxing --reinit (twice because strangely enough Curl always fails at first try).

Sorry for the inconvenience.

[AltGr]

Thanks for the report. Disabling sandboxing is not really a solution ; this was already fixed in #3957 though :)