mirror of
https://github.com/nix-community/nix-on-droid.git
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93 lines
2.5 KiB
Bash
93 lines
2.5 KiB
Bash
# Licensed under GNU Lesser General Public License v3 or later, see COPYING.
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# Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.
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# inspired by https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/system/etc/setup-etc.pl
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etc="${1}"
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static="/etc/static"
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new_etc="${2}"
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backup_extension="${3:-}"
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function atomic_symlink() {
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local source="${1}"
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local target="${2}"
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local target_tmp="${target}.tmp"
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mkdir -p "$(dirname "${target_tmp}")"
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ln -sf "${source}" "${target_tmp}"
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mv -T "${target_tmp}" "${target}"
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}
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# Remove dangling symlinks that point to /etc/static. These are
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# configuration files that existed in a previous configuration but not
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# in the current one.
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function cleanup() {
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local file
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for file in $(find "${etc}" -xtype l); do
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local target="$(readlink "${file}")"
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if [[ ! -L "${target}" ]]; then
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echo "Removing obsolete symlink '${file}'..."
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rm "${file}"
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fi
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done
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}
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# Returns 0 if the argument points to the files in /etc/static. That
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# means either argument is a symlink to a file in /etc/static or a
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# directory with all children being static.
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function is_static() {
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local path="${1}"
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if [[ -L "${path}" ]]; then
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[[ "$(readlink "${path}")" == ${static}/* ]]
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return
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fi
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if [[ -d "${path}" ]]; then
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local file
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for file in "${path}"/*; do
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is_static "${file}" || return
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done
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fi
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false
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}
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function link() {
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if [[ ! -d "${new_etc}" ]]; then
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return
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fi
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local name
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for name in $(find "${new_etc}/" -type l | sed -e "s,^${new_etc}/,,"); do
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local target="${etc}/${name}"
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mkdir -p "$(dirname "${target}")"
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if [[ -e "${target}" ]] && ! is_static "${target}"; then
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if [[ -n "${backup_extension}" ]]; then
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echo "Backing up '${target}' to '${target}${backup_extension}'..."
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cp "${target}" "${target}${backup_extension}"
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atomic_symlink "${static}/${name}" "${target}"
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else
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echo "Linking of ${target} failed. Please remove this file."
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fi
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else
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atomic_symlink "${static}/${name}" "${target}"
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fi
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done
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}
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# On initial build /etc/static is a directory instead of a symlink
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if [[ -d "${etc}/static" ]]; then
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rm --recursive "${etc}/static"
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fi
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# Atomically update /etc/static to point at the etc files of the
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# current configuration.
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atomic_symlink "${new_etc}" "${etc}/static"
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cleanup
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link
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