Date: Wed, 16 Sep 2015 11:58:38 -0500 From: Kevin Day <toasty@dragondata.com> To: Jan Bramkamp <crest@rlwinm.de> Cc: freebsd-fs@freebsd.org Subject: Re: Neutered devices in jails (per FS flag?) Message-ID: <7D445BFC-AB18-4EAD-8065-F0A934B1A479@dragondata.com> In-Reply-To: <55F99F5A.302@rlwinm.de> References: <E0C9157B-0FB7-4B2B-9BA2-5779DA7877FF@dragondata.com> <55F99F5A.302@rlwinm.de>
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> On 16/09/15 18:30, Kevin Day wrote: >> We’re currently using jails to allow servers to copy backups of themselves to a central backup server. The problem we’re having is with mknod/devices. Currently jails don’t allow device files to be created, which makes sense - you don’t want them to be able to bypass the jail by opening /dev/kmem or something. We want jails to be able to create device files, just not be able to open/use them. >> >> Has anyone given any thought to changing this behavior? Allowing jails to create/manipulate device files, but not actually opening them? I.e. instead of returning EPERM on creating the device, instead return EPERM on opening it? This would likely need to be a filesystem flag, because jails still require some devices to work (a separate devfs mount or something). We could make the jail’s /dev read only or use devfs so those devices still work, but have the parent jail directory with a “noopendev” flag or something similar. >> >> Has anyone gone down this path before? > > There is no reason to backup device files on FreeBSD because FreeBSD uses a dynamic devfs. Backup the devfs rules and devfs.conf instead of the device files. We’re backing up non-FreeBSD systems, as well as some software that creates its own devices inside a mini-chroot it needs to run.help
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