diff --git a/lib/install-nix.sh b/lib/install-nix.sh
index c3d25f8..904f487 100755
--- a/lib/install-nix.sh
+++ b/lib/install-nix.sh
@@ -6,9 +6,13 @@ if type -p nix &>/dev/null ; then
   exit
 fi
 
+# Create a temporary workdir
+workdir=$(mktemp -d)
+trap 'rm -rf "$workdir"' EXIT
+
 # Configure Nix
 add_config() {
-  echo "$1" | tee -a /tmp/nix.conf >/dev/null
+  echo "$1" | tee -a "$workdir/nix.conf" >/dev/null
 }
 # Set jobs to number of cores
 add_config "max-jobs = auto"
@@ -18,7 +22,7 @@ add_config "trusted-users = root $USER"
 if [[ $INPUT_EXTRA_NIX_CONFIG != "" ]]; then
   add_config "$INPUT_EXTRA_NIX_CONFIG"
 fi
-if [[ ! $INPUT_EXTRA_NIX_CONFIG =~ "experimental-features" ]]; then  
+if [[ ! $INPUT_EXTRA_NIX_CONFIG =~ "experimental-features" ]]; then
   add_config "experimental-features = nix-command flakes"
 fi
 
@@ -26,14 +30,14 @@ fi
 installer_options=(
   --no-channel-add
   --darwin-use-unencrypted-nix-store-volume
-  --nix-extra-conf-file /tmp/nix.conf
+  --nix-extra-conf-file "$workdir/nix.conf"
 )
 
 # only use the nix-daemon settings if on darwin (which get ignored) or systemd is supported
 if [[ $OSTYPE =~ darwin || -e /run/systemd/system ]]; then
   installer_options+=(
     --daemon
-    --daemon-user-count `python -c 'import multiprocessing as mp; print(mp.cpu_count() * 2)'`
+    --daemon-user-count "$(python -c 'import multiprocessing as mp; print(mp.cpu_count() * 2)')"
   )
 else
   # "fix" the following error when running nix*
@@ -42,20 +46,25 @@ else
 fi
 
 if [[ $INPUT_INSTALL_OPTIONS != "" ]]; then
-  IFS=' ' read -r -a extra_installer_options <<< $INPUT_INSTALL_OPTIONS
+  IFS=' ' read -r -a extra_installer_options <<< "$INPUT_INSTALL_OPTIONS"
   installer_options=("${extra_installer_options[@]}" "${installer_options[@]}")
 fi
 
-echo "installer options: ${installer_options[@]}"
+echo "installer options: ${installer_options[*]}"
 
 # There is --retry-on-errors, but only newer curl versions support that
-until curl -o /tmp/install -v --fail --retry 5 --retry-connrefused -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}" 
+curl_retries=5
+while ! curl -o "$workdir/install" -v --fail -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}"
 do
   sleep 1
+  ((curl_retries--))
+  if [[ $curl_retries -le 0 ]]; then
+    echo "curl retries failed" >&2
+    exit 1
+  fi
 done
 
-chmod +x /tmp/install
-sh /tmp/install "${installer_options[@]}"
+sh "$workdir/install" "${installer_options[@]}"
 
 if [[ $OSTYPE =~ darwin ]]; then
   # macOS needs certificates hints