Date: Fri, 16 Dec 2016 14:02:20 +0000 From: SK <fbstable@cps-intl.org> To: Alexander Leidinger <Alexander@leidinger.net>, SK <fbstable@cps-intl.org> Cc: Miroslav Lachman <000.fbsd@quip.cz>, freebsd-jail <freebsd-jail@freebsd.org> Subject: Re: ZFS and Jail :: nullfs mount :: nothing visible from host :: solved [partial] Message-ID: <d606c9ee-f5f6-55c5-0c99-01fd47a4a378@cps-intl.org> In-Reply-To: <20161216141540.Horde.zfu3fokeVx7FuFkk7_s-nbW@webmail.leidinger.net> References: <aa078173-e9f1-3f09-41d4-6613014b1119@cps-intl.org> <584986D0.3040109@quip.cz> <2b6346f8-ed02-0e6d-bd89-106098e7eb2d@cps-intl.org> <58499446.3050403@quip.cz> <eed9efad-9bac-9d36-b75e-c41f9ea72a8b@cps-intl.org> <5849C5BF.7020005@quip.cz> <fb56ab21-026b-408d-f712-ed7479e1f269@cps-intl.org> <584A9179.9060508@quip.cz> <b53fba06-bb7d-06d8-34a4-4677805fb175@cps-intl.org> <584A9D89.4040003@quip.cz> <3851c5d9-7646-b670-357e-ae937fcc7e8f@cps-intl.org> <584AB345.4080307@quip.cz> <33473585-3cb9-10d3-acf9-0a917c5a0079@cps-intl.org> <20161216141540.Horde.zfu3fokeVx7FuFkk7_s-nbW@webmail.leidinger.net>
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On 16/12/2016 13:15, Alexander Leidinger wrote:
> Quoting SK <fbstable@cps-intl.org> (from Mon, 12 Dec 2016 17:13:27
> +0000):
>
>> b) Alexander, I am still not able to do snapshot or any other action
>> from within my jail. My understanding is that you are using ezjail,
>> which might be doing something that my regular jail creation is
>> ommitting. If you do not mind sharing your configuration steps, I can
>> try to reproduce it at this end. If it is exactly as it is on the
>> site you pointed to earlier, please let me know, I will follow that
>> verbatim (even though I do not remember seeing anything there that I
>> have not tried already, but I might be mistaken).
>
> Do you use quotas on the datasets you want to add to the jail? If yes,
> try without. The man-page of zfs tells that this value can not be
> changed (but from the wording I would expect hat an already set value
> should work).
>
Hi Alexander, short answer, NO, I have not used quota yet
> ezjail is just a shell script which simplifies some things with jails.
> For a particular jail where I can manage the datasets which are handed
> over to the jail I have those settings in ezjail which correspond to
> the settings you can specify in jail.conf:
> ---snip---
> export jail_xyz_leidinger_net_devfs_ruleset="17"
> export jail_xyz_leidinger_net_zfs_datasets="space/something"
> export jail_xyz_leidinger_net_parameters="allow.mount allow.mount.zfs
> enforce_statfs=1"
> ---snip---
> Check if you have allow.mount and allow.mount.zfs for the jails in
> question.
>
Yes, those are in place.
> Note, "space/something" is not the root of the jail, it's a seperate
> dataset. Do not add the root of the jail as a dataset. Example bellow.
>
I think that might have been the cause for it to not work for me. I had
space/something/jailRoot, and defined that as the dataset for the jail
> devfs.rules part:
> ---snip---
> [devfsrules_unhide_zfs=12]
> add path zfs unhide
>
> [devfsrules_jail_withzfs=17]
> add include $devfsrules_hide_all
> add include $devfsrules_unhide_basic
> add include $devfsrules_unhide_login
> add include $devfsrules_unhide_zfs
> ---snip---
>
> The rc.conf inside this jail:
> ---snip---
> zfs_enable="YES"
> ---snip---
>
These are all in place as expected.
> For one of the filesystems I have set "zfs allow" permissions, but
> just that a specific user in the jail can do something on those FS
> without the need to switch to root. So as long as you try to do a zfs
> create/snapshot with an user with UID 0 inside the jail, the "zfs
> allow" part doesn't come into play.
>
> So assume space/jails/xyz.leidinger.net/ to be the dataset which
> contains the root of the jail but is not attached/attributed to the
> jail itself. space/jails/xyz.leidinger.net/data with mountpoint=none
> to be attributed ("zfs jail xyz space/jails/xyz.leidinger.net/data")
> to the jail (similar to the "space/something" in the ezjail config
> above, I have some iocage-managed jails were this works). In this case
> you should be able to do from inside the jail "zfs create -o
> mpuntpoint=/mnt space/jails/xyz.leidinger.net/data/test".
>
hmmm, I'm slightly confused at this point. Let me see if I can clarify
that in my brain
If I understand you correctly, what you are suggesting is, the dataset
used by the jail itself for its root/base cannot be "worked on" from
within the jail, but if I define a different dataset (under the same
branch below the jail dataset), and attribute it to the jail, then I can
manipulate that "other" dataset. Could you please confirm if I
understood it correctly?
>> And now to everyone, I am still confused about zfs set jailed=on. As
>> I mentioned on my previous emails, as soon as I do that, the dataset
>> vanishes from the host system (as I understand, that is expected
>> behaviour). Then the jail fails as it is unable to mount /dev, /proc
>
> From the zfs man page:
> ---snip---
> After a dataset is attached to a jail and the jailed property is
> set, a
> jailed file system cannot be mounted outside the jail, since the
> jail
> administrator might have set the mount point to an unacceptable
> value.
> ---snip---
>
> So yes, it is expected that it "vanishes", but it should be visible
> from the parent host at the place inside the jail FS subtree were it
> is mounted there (after setting the mountpoint of the dataset).
>
I think what you are trying to tell here is, unless and until that
"vanished" dataset is put to use (mounted) from inside the jail, it will
remain vanished/unusable from the host itself; however, once that
dataset is put to use, the host system should be able to "see" and maybe
even work on that dataset. Could you please confirm if I understood you
correctly?
>> and so on. I have to change jail.conf and comment out mount.devfs and
>> mount.procfs -- but than in turn makes /dev/zfs unavaulable and I
>> cannot do anything from inside the jail.
>
> Could it be that you try to attribute the root of the jail as a
> dataset into the jail?
>
Yes, I did. But now that I have a few more slightly different
explanation from you, once you confirm if my understanding is correct, I
am willing to give this a try.
Thanks again for your suggestions and guidlines.
Have a lovely weekend.
SK
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