From 8665b0d8b10dc612b9b3dd5174837278026739e4 Mon Sep 17 00:00:00 2001
From: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Date: Sat, 25 Jul 2015 23:57:55 +0300
Subject: [PATCH] extlinux-conf-builder: Fix warning when building in chroot

When using extlinux-conf-builder in a nix build using chroots, the
following error message could be seen:

/nix/store/XXX-extlinux-conf-builder.sh: line 121: cd: /nix/var/nix/profiles: No such file or directory

To avoid this, just skip the code path parsing /nix/var/nix/profiles
when $numGenerations (passed from the command line) is 0 (which is the
only legal value of $numGenerations in a nix build context).
---
 .../extlinux-conf-builder.sh                  | 22 ++++++++++---------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh b/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh
index 7da9c488f69..b9a42b2a196 100644
--- a/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh
+++ b/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh
@@ -115,16 +115,18 @@ EOF
 
 addEntry $default default >> $tmpFile
 
-# Add up to $numGenerations generations of the system profile to the menu,
-# in reverse (most recent to least recent) order.
-for generation in $(
-        (cd /nix/var/nix/profiles && ls -d system-*-link) \
-        | sed 's/system-\([0-9]\+\)-link/\1/' \
-        | sort -n -r \
-        | head -n $numGenerations); do
-    link=/nix/var/nix/profiles/system-$generation-link
-    addEntry $link $generation
-done >> $tmpFile
+if [ "$numGenerations" -gt 0 ]; then
+    # Add up to $numGenerations generations of the system profile to the menu,
+    # in reverse (most recent to least recent) order.
+    for generation in $(
+            (cd /nix/var/nix/profiles && ls -d system-*-link) \
+            | sed 's/system-\([0-9]\+\)-link/\1/' \
+            | sort -n -r \
+            | head -n $numGenerations); do
+        link=/nix/var/nix/profiles/system-$generation-link
+        addEntry $link $generation
+    done >> $tmpFile
+fi
 
 mv -f $tmpFile $target/extlinux/extlinux.conf