Hi, I'm seeing an issue with udev and libvirt-lxc. Libvirt-lxc creates /dev/ptmx as a symlink to /dev/pts/ptmx. When udev starts up, it checks the device type, sees ptmx is 'not right', and replaces it with a 'proper' ptmx. In lxc, /dev/ptmx is bind-mounted from /dev/pts/ptmx instead of being symlinked, so udev sees the right device type and leaves it alone. A patch like the following seems to work for me. Would there be any objections to this? >From 4c5035de52de7e06a0de9c5d0bab8c87a806cba7 Mon Sep 17 00:00:00 2001 From: Ubuntu <ubuntu(a)domU-12-31-39-14-F0-B3.compute-1.internal&gt; Date: Wed, 31 Aug 2011 18:15:54 +0000 Subject: [PATCH 1/1] make ptmx a bind mount rather than symlink udev on some systems checks the device type of /dev/ptmx, and replaces it if not as expected. The symlink created by libvirt-lxc therefore gets replaced. By creating it as a bind mount, the device type is correct and udev leaves it alone. Signed-off-by: Serge Hallyn <serge.hallyn(a)canonical.com&gt; --- src/lxc/lxc_container.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-) diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c index e425328..6991aec 100644 --- a/src/lxc/lxc_container.c +++ b/src/lxc/lxc_container.c @@ -543,18 +543,18 @@ static int lxcContainerPopulateDevices(void) } } + dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX); + if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 || + chmod("/dev/ptmx", 0666)) { + virReportSystemError(errno, "%s", + _("Failed to make device /dev/ptmx")); + return -1; + } + if (access("/dev/pts/ptmx", W_OK) == 0) { - if (symlink("/dev/pts/ptmx", "/dev/ptmx") < 0) { - virReportSystemError(errno, "%s", - _("Failed to create symlink /dev/ptmx to /dev/pts/ptmx")); - return -1; - } - } else { - dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX); - if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 || - chmod("/dev/ptmx", 0666)) { + if (mount("/dev/pts/ptmx", "/dev/ptmx", "ptmx", MS_BIND, NULL) < 0) { virReportSystemError(errno, "%s", - _("Failed to make device /dev/ptmx")); + _("Failed to bind-mount /dev/ptmx to /dev/pts/ptmx")); return -1; } }

Quoting Daniel Veillard (veillard(a)redhat.com): > On Wed, Aug 31, 2011 at 01:18:33PM -0500, Serge Hallyn wrote: > > Hi, > > > > I'm seeing an issue with udev and libvirt-lxc. Libvirt-lxc creates > > /dev/ptmx as a symlink to /dev/pts/ptmx. When udev starts up, it > > checks the device type, sees ptmx is 'not right', and replaces it > > with a 'proper' ptmx. > > > > In lxc, /dev/ptmx is bind-mounted from /dev/pts/ptmx instead of being > > symlinked, so udev sees the right device type and leaves it alone. > > > > A patch like the following seems to work for me. Would there be > > any objections to this? > > > > >From 4c5035de52de7e06a0de9c5d0bab8c87a806cba7 Mon Sep 17 00:00:00 2001 > > From: Ubuntu <ubuntu(a)domU-12-31-39-14-F0-B3.compute-1.internal&gt; > > Date: Wed, 31 Aug 2011 18:15:54 +0000 > > Subject: [PATCH 1/1] make ptmx a bind mount rather than symlink > > > > udev on some systems checks the device type of /dev/ptmx, and replaces it if > > not as expected. The symlink created by libvirt-lxc therefore gets replaced. > > By creating it as a bind mount, the device type is correct and udev leaves it > > alone. > > > > Signed-off-by: Serge Hallyn <serge.hallyn(a)canonical.com&gt; > > --- > > src/lxc/lxc_container.c | 20 ++++++++++---------- > > 1 files changed, 10 insertions(+), 10 deletions(-) > > > > diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c > > index e425328..6991aec 100644 > > --- a/src/lxc/lxc_container.c > > +++ b/src/lxc/lxc_container.c > > @@ -543,18 +543,18 @@ static int lxcContainerPopulateDevices(void) > > } > > } > > > > + dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX); > > + if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 || > > + chmod("/dev/ptmx", 0666)) { > > + virReportSystemError(errno, "%s", > > + _("Failed to make device /dev/ptmx")); > > + return -1; > > + } > > + > > if (access("/dev/pts/ptmx", W_OK) == 0) { > > - if (symlink("/dev/pts/ptmx", "/dev/ptmx") < 0) { > > - virReportSystemError(errno, "%s", > > - _("Failed to create symlink /dev/ptmx to /dev/pts/ptmx")); > > - return -1; > > - } > > - } else { > > - dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX); > > - if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 || > > - chmod("/dev/ptmx", 0666)) { > > + if (mount("/dev/pts/ptmx", "/dev/ptmx", "ptmx", MS_BIND, NULL) < 0) { > > virReportSystemError(errno, "%s", > > - _("Failed to make device /dev/ptmx")); > > + _("Failed to bind-mount /dev/ptmx to /dev/pts/ptmx")); > > return -1; > > } > > } > > Hum, if we do a mount, I would expect to do an unmount somewhere. > Also the lifetime of the mount and the symlink is really different, > a recursive remove when destroying the container would lead to no > resource leak but I think that for a bind mount we absolutely have > to clean it up. This code is being done in a private mount namespace, so the mount will get automatically cleaned up when that namespace exits.

Hi, I'm seeing an issue with udev and libvirt-lxc. Libvirt-lxc creates /dev/ptmx as a symlink to /dev/pts/ptmx. When udev starts up, it checks the device type, sees ptmx is 'not right', and replaces it with a 'proper' ptmx.

In lxc, /dev/ptmx is bind-mounted from /dev/pts/ptmx instead of being symlinked, so udev sees the right device type and leaves it alone. A patch like the following seems to work for me. Would there be any objections to this? >From 4c5035de52de7e06a0de9c5d0bab8c87a806cba7 Mon Sep 17 00:00:00 2001 From: Ubuntu <ubuntu(a)domU-12-31-39-14-F0-B3.compute-1.internal&gt; Date: Wed, 31 Aug 2011 18:15:54 +0000 Subject: [PATCH 1/1] make ptmx a bind mount rather than symlink udev on some systems checks the device type of /dev/ptmx, and replaces it if not as expected. The symlink created by libvirt-lxc therefore gets replaced. By creating it as a bind mount, the device type is correct and udev leaves it alone. Signed-off-by: Serge Hallyn <serge.hallyn(a)canonical.com&gt; --- src/lxc/lxc_container.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-) diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c index e425328..6991aec 100644 --- a/src/lxc/lxc_container.c +++ b/src/lxc/lxc_container.c @@ -543,18 +543,18 @@ static int lxcContainerPopulateDevices(void) } } + dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX); + if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 || + chmod("/dev/ptmx", 0666)) { + virReportSystemError(errno, "%s", + _("Failed to make device /dev/ptmx")); + return -1; + } + if (access("/dev/pts/ptmx", W_OK) == 0) { - if (symlink("/dev/pts/ptmx", "/dev/ptmx") < 0) { - virReportSystemError(errno, "%s", - _("Failed to create symlink /dev/ptmx to /dev/pts/ptmx")); - return -1; - } - } else { - dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX); - if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 || - chmod("/dev/ptmx", 0666)) { + if (mount("/dev/pts/ptmx", "/dev/ptmx", "ptmx", MS_BIND, NULL) < 0) { virReportSystemError(errno, "%s", - _("Failed to make device /dev/ptmx")); + _("Failed to bind-mount /dev/ptmx to /dev/pts/ptmx")); return -1; } }