[lxc-users] Use image file for unprivileged containers

[Dr. Todor Dimitrov]

For the sake of completeness, here are the commands to create the image:

---
dd if=/dev/zero of=test.img bs=1M count=10
mkfs.ext4 -c test.img
mount -o loop test.img /mnt/test

# copy root-fs to /mnt/test
# perform id shifting if necessary

umount /mnt/test
---

Thanks for the support!

Todor

> On 15. Jun 2018, at 18:20, Christian Brauner <christian at brauner.io <mailto:christian at brauner.io>> wrote:
> 
> On Fri, Jun 15, 2018 at 06:03:06PM +0200, Dr. Todor Dimitrov wrote:
>>>> but it will have to be idshifted before the start.
>> 
>> So the id shifting will be also done automatically? Once or on each start?
> 
> No, the id shifting is *not* done by LXC. Only the *mount*.
> 
>> 
>> What about the format of the image file? Is there any documentation or samples on this? I assume a dd img with a single partition (e.g. ext4) should be OK?
> 
> We don't really handle partitions, I think. You can setup a privileged
> container with:
> 
> sudo lxc-create ttt -t download -B loop -- -d alpine -r edge -a amd64
> 
> and then take a look at the loop file that got created. This is the
> format we support.
> 
> Christian
> 
>> 
>> Thanks,
>> Todor
>> 
>>> On 15. Jun 2018, at 17:50, Christian Brauner <christian at brauner.io <mailto:christian at brauner.io>> wrote:
>>> 
>>> On Fri, Jun 15, 2018 at 05:02:50PM +0200, Dr. Todor Dimitrov wrote:
>>>> Hallo Christian,
>>>> 
>>>> do I have to manually perform the loop mount? I thought this was done by the LXC runtime.
>>> 
>>> Yes, the mount is performed. If you have manually prepared an image you
>>> can do:
>>> 
>>> lxc.rootfs.path = loop:/path/to/file
>>> 
>>>> 
>>>> What is actually meant by “image file” inside the documentation:
>>>> 
>>>> “
>>>> lxc.rootfs.path - specify the root file system for the container. It can be an image file, a directory or a block device. If not specified, the container shares its root file system with the host.
>>>> "
>>>> 
>>>> Todor
>>>> 
>>>>> On 15. Jun 2018, at 16:39, Christian Brauner <christian at brauner.io <mailto:christian at brauner.io>> wrote:
>>>>> 
>>>>> On Fri, Jun 15, 2018 at 10:28:34AM +0200, Dr. Todor Dimitrov wrote:
>>>>>> Hallo,
>>>>>> 
>>>>>> is it possible to use an image file with “lxc.rootfs.path” for an
>>>>>> unprivileged container? If possible, is it necessary to have the
>>>>>> correct file ownerships within the image or are these automatically
>>>>>> adjusted on start, e.g. on mount.
>>>>> 
>>>>> If by image you mean something you can mount on a loop device then yes
>>>>> but it will have to be idshifted before the start.
>>>>> 
>>>>> Christian
>>>>> 
>>>>>> 
>>>>>> Thanks in advance,
>>>>>> Todor
>>>>>> 
>>>>> 
>>>>> 
>>>>> 
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>>> 
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> 
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