[libvirt-users] libvirt_lxc and sysfs
Gao feng
gaofeng at cn.fujitsu.com
Mon Jun 10 05:58:29 UTC 2013
On 06/10/2013 01:41 PM, pr.G wrote:
> On Mon, Jun 10, 2013 at 09:29:32AM +0400, свящ. Георгий Гольцов wrote:
>> On Mon, Jun 10, 2013 at 09:07:08AM +0800, Gao feng wrote:
>>> On 06/09/2013 08:14 PM, pr.G wrote:
>>>> Hello.
>>>>
>>>> Is it possible to start container via libvirt_lxc without mounting /sys
>>>> inside container?
>>>>
>>>> When I start container via lxc-start and do not add mount point to config,
>>>> then /sys inside container is empty.
>>>>
>>>> When I do it via virsh -c lxc:// container.xml, then
>>>> /sys contains sysfs of the host and /sys on host becomes remounting read-only.
>>>
>>> how can it be true? Can you post your /proc/mounts on host and container?
>>>
>>>>
>>>> Am I doing something wrong or is this feature of libvirt_lxc?
>>>>
>>>
>>> Absolutely it's not a feature.
>>>
>>> Thanks!
>>>
> Thanks for the quick reply.
> I was surprised too. I didn't post /proc/mounts to container.
I mean show the /proc/mounts of container and host
in container:
cat /proc/mounts
[root at Donkey /]# cat /proc/mounts
rootfs / rootfs rw 0 0
devpts /dev/pts devpts rw,nosuid,relatime,gid=5,mode=620,ptmxmode=666 0 0
devfs /dev tmpfs rw,nosuid,relatime,size=64k,mode=755 0 0
/dev/sdb2 / ext4 rw,relatime,data=ordered 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
proc /proc/sys proc ro,relatime 0 0
sysfs /sys sysfs ro,relatime 0 0
libvirt /proc/meminfo fuse rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other 0 0
tmpfs /sys/fs/cgroup tmpfs rw,nosuid,nodev,noexec,relatime,size=64k,mode=755,uid=1000,gid=1000 0 0
cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpuacct,cpu 0 0
cgroup /sys/fs/cgroup/cpuset cgroup rw,nosuid,nodev,noexec,relatime,cpuset 0 0
cgroup /sys/fs/cgroup/memory cgroup rw,nosuid,nodev,noexec,relatime,memory 0 0
cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0
cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0
cgroup /sys/fs/cgroup/net_cls cgroup rw,nosuid,nodev,noexec,relatime,net_cls 0 0
cgroup /sys/fs/cgroup/perf_event cgroup rw,nosuid,nodev,noexec,relatime,perf_event 0 0
devpts /dev/ptmx devpts rw,nosuid,relatime,gid=5,mode=620,ptmxmode=666 0 0
and in host
[root at Donkey libvirt]# cat /proc/mounts
rootfs / rootfs rw 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
devtmpfs /dev devtmpfs rw,nosuid,size=5081344k,nr_inodes=1270336,mode=755 0 0
securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
tmpfs /run tmpfs rw,nosuid,nodev,mode=755 0 0
tmpfs /sys/fs/cgroup tmpfs rw,nosuid,nodev,noexec,mode=755 0 0
cgroup /sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd 0 0
pstore /sys/fs/pstore pstore rw,nosuid,nodev,noexec,relatime 0 0
cgroup /sys/fs/cgroup/cpuset cgroup rw,nosuid,nodev,noexec,relatime,cpuset 0 0
cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpuacct,cpu 0 0
cgroup /sys/fs/cgroup/memory cgroup rw,nosuid,nodev,noexec,relatime,memory 0 0
cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0
cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0
cgroup /sys/fs/cgroup/net_cls cgroup rw,nosuid,nodev,noexec,relatime,net_cls 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0
cgroup /sys/fs/cgroup/perf_event cgroup rw,nosuid,nodev,noexec,relatime,perf_event 0 0
cgroup /sys/fs/cgroup/hugetlb cgroup rw,nosuid,nodev,noexec,relatime,hugetlb 0 0
....
> libvirt_lxc did it for me.
> I read http://libvirt.org/drvlxc.html about Filesystem mounts:
> "
> In the absence of any explicit configuration, the container will
> inherit the host OS filesystem mounts. A number of mount points will be
> made read only, or re-mounted with new instances to provide container
> specific data. The following special mounts are setup by libvirt
>
> * /dev a new "tmpfs" pre-populated with authorized device nodes
> * /dev/pts a new private "devpts" instance for console devices
> * /sys the host "sysfs" instance remounted read-only
> * /proc a new instance of the "proc" filesystem
> * /proc/sys the host "/proc/sys" bind-mounted read-only
> * /sys/fs/selinux the host "selinux" instance remounted read-only
> * /sys/fs/cgroup/NNNN the host cgroups controllers bind-mounted to
> * only expose the sub-tree associated with the container
> * /proc/meminfo a FUSE backed file reflecting memory limits of the
> * container
> "
> Can I disable this behavior?
> How do I specify an explicit configuration?
This can't be disabled and it's no need to disable this.
>
> my container.xml: (The entire xml file is shown in the my original post)
>> ...
>> <devices>
>> <emulator>/usr/lib/libvirt/libvirt_lxc</emulator>
>> <filesystem type='mount'>
>> <source dir='/var/lxc/ns1/rootfs'/>
>> <target dir='/'/>
>> </filesystem>
>> ...
>> </device>
>> ...
>>
Your configuration looks good, In container,the sysfs is mounted as read-only default.
Since we don't want user in container to change some sysfs-configuration of host.
Thanks
Gao.
>>
>>>> Thanks.
>>>>
>>>> root at host:~# uname -a
>>>> Linux host 3.2.0-4-amd64 #1 SMP Debian 3.2.41-2+deb7u2 x86_64 GNU/Linux
>>>>
>>>> root at host:~# cat /etc/os-release
>>>> PRETTY_NAME="Debian GNU/Linux 7.0 (wheezy)"
>>>> ...
>>>>
>>>> root at host:~# dpkg -l | grep libvirt
>>>> ii libvirt-bin 0.9.12-11 amd64 programs for the libvirt library
>>>> ii libvirt0 0.9.12-11 amd64 library for interfacing with different virtualization systems
>>>>
>>>>
>>>> container.xml:
>>>> <domain type='lxc'>
>>>> <name>ns1</name>
>>>> <memory>524288</memory>
>>>> <os>
>>>> <type>exe</type>
>>>> <init>/sbin/init</init>
>>>> </os>
>>>> <vcpu>1</vcpu>
>>>> <clock offset='utc'/>
>>>> <on_poweroff>destroy</on_poweroff>
>>>> <on_reboot>restart</on_reboot>
>>>> <on_crash>destroy</on_crash>
>>>> <devices>
>>>> <emulator>/usr/lib/libvirt/libvirt_lxc</emulator>
>>>> <filesystem type='mount'>
>>>> <source dir='/var/lxc/ns1/rootfs'/>
>>>> <target dir='/'/>
>>>> </filesystem>
>>>> <interface type='bridge'>
>>>> <source bridge='br0'/>
>>>> <mac address='52:54:00:de:74:06'/>
>>>> </interface>
>>>> <console type='pty' />
>>>> </devices>
>>>> </domain>
>>>>
>>>>
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>>>>
>>>
>
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