nix-surgeon: tool for repairing corrupted nix store paths

nix-surgeon.sh

#! /usr/bin/env bash

NIX_STORE=${NIX_STORE:-"/nix/store"};
store_path=$1;

# check if path is actually broken
if nix-store --verify-path $store_path; then exit 0; fi;

# abuse --check flag to get a fresh, non-substituted rebuild of the path
# TODO: GC?
echo "building a new copy of $store_path";
nix-store --realise --check -K $(nix-store -q --deriver $store_path);

echo "repairing $store_path";
unshare -m sh -c " \
    mount -o remount,rw $NIX_STORE; \
    rm -rf $store_path; \
    nix-store --dump $store_path.check | nix-store --restore $store_path; \
    "

nix-store --verify-path $store_path;