[lxc-devel] [lxd/master] lxd/dameon: Add LXD_EXEC_PATH to override execPath

[stgraber on Github]

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From 1aee50f0386481c55ac8c6bb8615bf3e716701d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber at ubuntu.com>
Date: Mon, 20 Nov 2017 23:20:12 -0500
Subject: [PATCH] lxd/dameon: Add LXD_EXEC_PATH to override execPath
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This is needed for the LXD snap.

The pre-start/post-stop container hooks point to the LXD path and are
called when the container shuts down.

As the snapd paths include the revision of the daemon, a system which
got updated would then have a hook path pointing to a non-existing
binary.

This extra env variable allows us to point to the "current" path in the
snap, which is effectively a symlink to whichever is the latest binary.

Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
---
 doc/environment.md | 3 ++-
 lxd/util/sys.go    | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/doc/environment.md b/doc/environment.md
index e20ae9c79..fae35be81 100644
--- a/doc/environment.md
+++ b/doc/environment.md
@@ -20,5 +20,6 @@ Name                            | Description
 # Server environment variable
 Name                            | Description
 :---                            | :----
-`LXD_SECURITY_APPARMOR`         | If set to `false`, forces AppArmor off
+`LXD_EXEC_PATH`                 | Full path to the LXD binary (used when forking subcommands)
 `LXD_LXC_TEMPLATE_CONFIG`       | Path to the LXC template configuration directory
+`LXD_SECURITY_APPARMOR`         | If set to `false`, forces AppArmor off
diff --git a/lxd/util/sys.go b/lxd/util/sys.go
index a9d91f634..5532f8704 100644
--- a/lxd/util/sys.go
+++ b/lxd/util/sys.go
@@ -152,6 +152,11 @@ func RuntimeLiblxcVersionAtLeast(major int, minor int, micro int) bool {
 }
 
 func GetExecPath() string {
+	execPath := os.Getenv("LXD_EXEC_PATH")
+	if execPath != "" {
+		return execPath
+	}
+
 	execPath, err := os.Readlink("/proc/self/exe")
 	if err != nil {
 		execPath = "bad-exec-path"