mirror of
https://github.com/nix-community/impermanence
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66 lines
2.4 KiB
Bash
66 lines
2.4 KiB
Bash
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#!/usr/bin/env bash
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set -o nounset
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set -o errexit
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set -o pipefail
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set -o errtrace
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trap 'echo Error when executing ${BASH_COMMAND} at line ${LINENO}! >&2' ERR
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# Given a source directory, /source, and a target directory,
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# /target/foo/bar/bazz, we want to "clone" the target structure
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# from source into the target. Essentially, we want both
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# /source/target/foo/bar/bazz and /target/foo/bar/bazz to exist
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# on the filesystem. More concretely, we'd like to map
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# /state/etc/ssh/example.key to /etc/ssh/example.key
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#
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# To achieve this, we split the target's path into parts -- target, foo,
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# bar, bazz -- and iterate over them while accumulating the path
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# (/target/, /target/foo/, /target/foo/bar, and so on); then, for each of
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# these increasingly qualified paths we:
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# 1. Ensure both /source/qualifiedPath and qualifiedPath exist
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# 2. Copy the ownership of the source path to the target path
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# 3. Copy the mode of the source path to the target path
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# Get inputs from command line arguments
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if [[ "$#" != 2 ]]; then
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printf "Error: 'create-directories.bash' requires *two* args.\n" >&2
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exit 1
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fi
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sourceBase="$1"
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target="$2"
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# trim trailing slashes the root of all evil
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sourceBase="${sourceBase%/}"
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target="${target%/}"
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# check that the source exists and warn the user if it doesn't
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realSource="$(realpath "$sourceBase$target")"
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if [[ ! -d "$realSource" ]]; then
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printf "Warning: Source directory '%s' does not exist; it will be created for you. Make sure the permissions are correct!\n" "$realSource"
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fi
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# iterate over each part of the target path, e.g. var, lib, iwd
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previousPath="/"
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for pathPart in $(echo "$target" | tr "/" " "); do
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# construct the incremental path, e.g. /var, /var/lib, /var/lib/iwd
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currentTargetPath="$previousPath$pathPart/"
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# construct the source path, e.g. /state/var, /state/var/lib, ...
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currentSourcePath="$sourceBase$currentTargetPath"
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# create the source and target directories if they don't exist
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[[ -d "$currentSourcePath" ]] || mkdir "$currentSourcePath"
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[[ -d "$currentTargetPath" ]] || mkdir "$currentTargetPath"
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# resolve the source path to avoid symlinks
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currentRealSourcePath="$(realpath "$currentSourcePath")"
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# synchronize perms between source and target
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chown --reference="$currentRealSourcePath" "$currentTargetPath"
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chmod --reference="$currentRealSourcePath" "$currentTargetPath"
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# lastly we update the previousPath to continue down the tree
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previousPath="$currentTargetPath"
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done
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