[Lxc-users] lxc-start leaves temporary pivot dir behind

[Ferenc Wagner]

Ferenc Wagner <wferi at niif.hu> writes:

> Daniel Lezcano <dlezcano at fr.ibm.com> writes:
>
>> Ferenc Wagner wrote:
>>
>>> Daniel Lezcano <daniel.lezcano at free.fr> writes:
>>>
>>>> Ferenc Wagner wrote:
>>>>
>>>>> While playing with lxc-start, I noticed that /tmp is infested by
>>>>> empty lxc-r* directories: [...] Ok, this name comes from lxc-rootfs
>>>>> in conf.c:setup_rootfs.  After setup_rootfs_pivot_root returns, the
>>>>> original /tmp is not available anymore, so rmdir(tmpname) at the
>>>>> bottom of setup_rootfs can't achieve much.  Why is this temporary
>>>>> name needed anyway?  Is pivoting impossible without it?
>>>>
>>>> That was put in place with chroot, before pivot_root, so the distro's
>>>> scripts can remount their '/' without failing.
>>>>
>>>> Now we have pivot_root, I suppose we can change that to something cleaner...
>>>
>>> Like simply nuking it?  Shall I send a patch?
>>
>> Sure, if we can kill it, I will be glad to take your patch :)
>
> I can't see any reason why lxc-start couldn't do without that temporary
> recursive bind mount of the original root.  If neither do you, I'll
> patch it out and see if it still flies.

For my purposes the patch below works fine.  I only run applications,
though, not full systems, so wider testing is definitely needed.

Thanks,
Feri.

>From 98b24c13f809f18ab8969fb4d84defe6f812b25c Mon Sep 17 00:00:00 2001
From: Ferenc Wagner <wferi at niif.hu>
Date: Thu, 6 May 2010 14:47:39 +0200
Subject: [PATCH] no need to use a temporary directory for pivoting

That was put in place before lxc-start started using pivot_root, so
the distro scripts can remount / without problems.

Signed-off-by: Ferenc Wagner <wferi at niif.hu>
---
 src/lxc/conf.c |   28 +++-------------------------
 1 files changed, 3 insertions(+), 25 deletions(-)

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index b27a11d..4379a32 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -588,37 +588,15 @@ static int setup_rootfs_pivot_root(const char *rootfs, const char *pivotdir)
 
 static int setup_rootfs(const char *rootfs, const char *pivotdir)
 {
-	char *tmpname;
-	int ret = -1;
-
 	if (!rootfs)
 		return 0;
 
-	tmpname = tempnam("/tmp", "lxc-rootfs");
-	if (!tmpname) {
-		SYSERROR("failed to generate temporary name");
-		return -1;
-	}
-
-	if (mkdir(tmpname, 0700)) {
-		SYSERROR("failed to create temporary directory '%s'", tmpname);
-		return -1;
-	}
-
-	if (mount(rootfs, tmpname, "none", MS_BIND|MS_REC, NULL)) {
-		SYSERROR("failed to mount '%s'->'%s'", rootfs, tmpname);
-		goto out;
-	}
-
-	if (setup_rootfs_pivot_root(tmpname, pivotdir)) {
+	if (setup_rootfs_pivot_root(rootfs, pivotdir)) {
 		ERROR("failed to pivot_root to '%s'", rootfs);
-		goto out;
+		return -1;
 	}
 
-	ret = 0;
-out:
-	rmdir(tmpname);
-	return ret;
+	return 0;
 }
 
 static int setup_pts(int pts)
-- 
1.6.5