install script: don't abort when "nix-channel --update" fails

Instead, print a message about what happened and tell the user what can
be done (run "[sudo -i] nix-channel --update nixpkgs" again at a later
time). This change allows installing Nix when you're offline.

Since the multi-user installer is so verbose, the message isn't printed
until the end.

Fixes issue #2650 ("installation without internet connection").

1 files changed, 9 insertions, 1 deletions

diff --git a/scripts/install-multi-user.sh b/scripts/install-multi-user.sh
index 6ee8dd48582e..3d2acaac82f5 100644
--- a/scripts/install-multi-user.sh
+++ b/scripts/install-multi-user.sh
@@ -240,10 +240,16 @@ EOF
 }
 trap finish_fail EXIT
 
+channel_update_failed=0
 function finish_success {
     finish_cleanup
 
     ok "Alright! We're done!"
+    if [ "x$channel_update_failed" = x1 ]; then
+        echo ""
+        echo "But fetching the nixpkgs channel failed. (Are you offline?)"
+        echo "To try again later, run \"sudo -i nix-channel --update nixpkgs\"."
+    fi
     cat <<EOF
 
 Before Nix will work in your existing shells, you'll need to close
@@ -737,7 +743,9 @@ setup_default_profile() {
     # otherwise it will be lost in environments where sudo doesn't pass
     # all the environment variables by default.
     _sudo "to update the default channel in the default profile" \
-          HOME="$ROOT_HOME" NIX_SSL_CERT_FILE="$NIX_SSL_CERT_FILE" "$NIX_INSTALLED_NIX/bin/nix-channel" --update nixpkgs
+          HOME="$ROOT_HOME" NIX_SSL_CERT_FILE="$NIX_SSL_CERT_FILE" "$NIX_INSTALLED_NIX/bin/nix-channel" --update nixpkgs \
+          || channel_update_failed=1
+
 }