Reinstallation hangs after updating MacOS Big Sur from 10.6.0 to 10.6.3

[cmack]

Describe the bug

My reinstallation of multi-user nix hangs stops when trying to copy an identical file. This is similar to #6009 but my scenario did not involve encrypted volume problems so I'm filing separately in abundance of caution.

Steps To Reproduce

1. Have an working installation of multi-user Nix 2.5.1 on MacOS Big Sur 10.6.0
2. Use macOS system update to upgrade to Big Sur 10.6.3
3. Reboot and find nix-channel --version doesn't work any longer (admittedly this could be where I caused myself problems due to nix inexperience and unhelpful google results ..and macos)
4. Decide that upgrading nix to 2.6.0 is the way to fix my problems, download and run multiuser macos installation script for nix 2.6.0
5. Here is the final error. I'll provide a full log at the bottom:

~~> Installing Nix

---- sudo execution ------------------------------------------------------------
I am executing:

    $ sudo cp -RLp ./store/015rgxn5xx5awkz48yhh9c9n1bsvvivm-libiconv-50 ./store/0cgmjzpv8xy2ll3z1wwpnj5js58ddp07-libcxx-7.1.0 ./store/0ma0hl096m764z10k1lp5fwvl7pzm16a-boehm-gc-8.0.4 ./store/0qkfjbhpq6v36rdy8j5arnxdrapv3i3m-libkrb5-1.18 ./store/1j82hjxc28ccvi8i4f3zqg8gia3zvcnp-openssl-1.1.1l ./store/2p623hvx2ha2clb6ry2cyyd0jdz0qyd8-aws-c-cal-0.4.5 ./store/3saax6q1s9im5p80nxhdqpjmw3g4nzg8-curl-7.76.1 ./store/4hdh249mvpywd9qka6awibgdils1mf2a-libcpuid-0.5.1 ./store/5l22hgwshwq7sqn7wqdxmpq1q2100br8-libarchive-3.5.2-lib ./store/5py10pm1w9ziv4qgsk80ghqxwf51syv1-brotli-1.0.9-lib ./store/69dskd4cabzl6cxch5lbfss73l3r6bya-apple-framework-Security ./store/6p1mr7avpnni6n7ssxqjfj7fa4sy00x0-openssl-1.1.1l ./store/79q6vp06aj2p550f2wgn9zywywm6pmir-libcxxabi-7.1.0 ./store/80lzb3092v637di7ihbwx888isy1w1li-libssh2-1.9.0 ./store/8vdyi0ifc098g6cnw38pqbwi78drkgj0-aws-sdk-cpp-1.8.121 ./store/95n0y1033piss1slf99is61a3zc0yv0p-libsodium-1.0.18 ./store/9lzf8irh5b0v9vix6j847vyhqp5lxwq6-aws-checksums-0.1.11 ./store/afpdl5r9jnb8bx42nzpqi0c6g1flwldg-Libsystem-1238.60.2 ./store/cpgyi9khbv1yg2i22vg0zhmsnif9aih9-bash-4.4-p23 ./store/d0dxz2ysp7xd49l8w2n738pps2k3d7m9-aws-c-io-0.9.1 ./store/g8fbhc5bn0mi29gw3jhxm4hrlif00nlz-brotli-1.0.9-lib ./store/gb9nkla1b2zplgbn7j01q7l8hswgwcnb-xz-5.2.5 ./store/hw5v03wnc0k1pwgiyhblwlxb1fx5zyx8-nix-2.6.0 ./store/i0zac1vw0ra6g2mg701m3kc9xbi24lgg-zlib-1.2.11 ./store/i8rksi0pqzcbmsfs48kwp5nvih8mfn4a-bzip2-1.0.6.0.2 ./store/jd1l64vr0b5y1qvdsrminn53gkvamm32-editline-1.17.1 ./store/k5i7ralzb1w0jx3fyn8q9n80kwv16l33-swift-corefoundation ./store/k5vggrdqvyb4lgyy7ck7s7wlyfiqfh9k-sqlite-3.35.5 ./store/k7vg16vz0dsxjfxv0a2hkxw7y4msv7la-zstd-1.4.9 ./store/kldmyqpq68qqp5y80fa0y66zlfzalm7m-aws-c-event-stream-0.2.7 ./store/kvcxphxg6pwp9wgvb468l5m5sbd5krrs-aws-c-common-0.5.5 ./store/kvvpk2vdlh4pc8qyfxcd1rlzyr4zb3bp-libssh2-1.9.0 ./store/n2a3hyr6kmadwpivr0x36xylj9j0wcja-curl-7.76.1 ./store/nqfyfv5lq0n00iqakzcpbl5cq2dkwdz8-libxml2-2.9.12 ./store/r0023xa974x14h83jwrcc8x6i54n9b78-libxml2-2.9.12 ./store/s3dhqrdq6mj935q2pfgw373w0n8459m1-apple-framework-IOKit ./store/wil7lqvyfb18hkdv0bdrf5h0f9y5v9lm-ICU-66108 ./store/wiqcjg66s7sb6cais8pifrk3l9cpkrmq-nss-cacert-3.66 ./store/x0r180c6xm8zgfnczhi27831ly56k888-nghttp2-1.43.0-lib ./store/z31hmk06a669vhjaj6ahn5x2i73l2bsy-libkrb5-1.18 ./store/zqigm4h2qjj8pr6z47aj4zf3rasrb6fy-nghttp2-1.43.0-lib /nix/store/

to copy the basic Nix files to the new store at /nix/store

cp: /nix/store/69dskd4cabzl6cxch5lbfss73l3r6bya-apple-framework-Security/Library/Frameworks/Security.framework/Resources and ./store/69dskd4cabzl6cxch5lbfss73l3r6bya-apple-framework-Security/Library/Frameworks/Security.framework/Resources are identical (not copied).
cp: /nix/store/69dskd4cabzl6cxch5lbfss73l3r6bya-apple-framework-Security/Library/Frameworks/Security.framework/Versions/A/Resources and ./store/69dskd4cabzl6cxch5lbfss73l3r6bya-apple-framework-Security/Library/Frameworks/Security.framework/Versions/A/Resources are identical (not copied).
cp: /nix/store/69dskd4cabzl6cxch5lbfss73l3r6bya-apple-framework-Security/Library/Frameworks/Security.framework/Versions/Current/Resources and ./store/69dskd4cabzl6cxch5lbfss73l3r6bya-apple-framework-Security/Library/Frameworks/Security.framework/Versions/Current/Resources are identical (not copied).
cp: /nix/store/s3dhqrdq6mj935q2pfgw373w0n8459m1-apple-framework-IOKit/Library/Frameworks/IOKit.framework/Resources and ./store/s3dhqrdq6mj935q2pfgw373w0n8459m1-apple-framework-IOKit/Library/Frameworks/IOKit.framework/Resources are identical (not copied).
cp: /nix/store/s3dhqrdq6mj935q2pfgw373w0n8459m1-apple-framework-IOKit/Library/Frameworks/IOKit.framework/Versions/A/Resources and ./store/s3dhqrdq6mj935q2pfgw373w0n8459m1-apple-framework-IOKit/Library/Frameworks/IOKit.framework/Versions/A/Resources are identical (not copied).
cp: /nix/store/s3dhqrdq6mj935q2pfgw373w0n8459m1-apple-framework-IOKit/Library/Frameworks/IOKit.framework/Versions/Current/Resources and ./store/s3dhqrdq6mj935q2pfgw373w0n8459m1-apple-framework-IOKit/Library/Frameworks/IOKit.framework/Versions/Current/Resources are identical (not copied).

---- oh no! --------------------------------------------------------------------

Expected behavior

To continue through the installation process even if copying files that are identical to destination.

nix-env --version output
N/A; couldn't complete installation

Additional context
nix-install-output.txt

I will probably try deleting these files as #6009 did to continue but still filed since hanging on copying identical files seems undesirable.

Edit
It did complete after deleting the directories. This was the output at the end with nix-shell -p nix-info --run "nix-info -m"

 - system: `"x86_64-darwin"`
 - host os: `Darwin 20.6.0, macOS 10.16`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.5.1`
 - channels(charlie): `"nixpkgs-21.11pre321137.8e1eab9eae4"`
 - channels(root): `"nixpkgs"`
 - nixpkgs: `/Users/charlie/.nix-defexpr/channels/nixpkgs`

I guess I wasn't downloading nix 2.6.0 after all even though this is what I saw at download time

[abathur]

For posterity, since it sounds like you got your own system sorted:

1. The immediate error is probably a side-effect of the switch to cp from rsync in Remove rsync usage in the installer #5150, and less-directly the decision to try and allow people to keep existing Nix Store volumes instead of forcing a wipe of them.
2. The immediate fix is finding a POSIX or otherwise cross-platform way to make the current copy operation idempotent when the files are already present.
3. Another possible fix is finishing out support for curing every install artifact (currently just macOS-specific artifacts are handled; this would also get us --uninstall support for mostly-free...); initial steps described in https://discourse.nixos.org/t/anyone-up-for-picking-at-some-nix-onboarding-improvements/13152