expand docs for unshare mode

This commit is contained in:
Johannes 'josch' Schauer 2020-04-12 09:10:30 +02:00
parent a0c097a6fa
commit 2ce9555dc5
Signed by untrusted user: josch
GPG key ID: F2CBA5C78FBD83E1

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@ -5139,12 +5139,29 @@ by the _apt user, then apt sandboxing will be automatically disabled.
This mode uses Linux user namespaces to allow unprivileged use of chroot and
creation of files that appear to be owned by the superuser inside the unshared
namespace. A directory chroot created with this mode will end up with wrong
ownership information. Choose to create a tarball instead. This mode requires
the sysctl C<kernel.unprivileged_userns_clone> being set to C<1>. B<SETTING
THIS OPTION HAS SECURITY IMPLICATIONS>. Refer to
namespace. A tarball created in this mode should be bit-by-bit identical to a
tarball created with the B<root> mode. This mode requires the sysctl
C<kernel.unprivileged_userns_clone> being set to C<1>. B<SETTING THIS OPTION
HAS SECURITY IMPLICATIONS>. Refer to
L<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=898446>
A directory chroot created with this mode will end up with wrong ownership
information. For correct ownership information, the directory must be accessed
from a user namespace with the right subuid/subgid offset, like so:
$ lxc-usernsexec -- lxc-unshare -s 'MOUNT|PID|UTSNAME|IPC' -- \
> /usr/sbin/chroot ./debian-rootfs /bin/bash
Or without LXC:
$ mmdebstrap --unshare-helper /usr/sbin/chroot ./debian-rootfs /bin/bash
Or, if you don't mind using superuser privileges and have systemd-nspawn
available and you know your subuid/subgid offset (100000 in this example):
$ sudo systemd-nspawn --private-users=100000 \
> --directory=./debian-rootfs /bin/bash
=item B<fakeroot>, B<fakechroot>
This mode will exec B<mmdebstrap> again under C<fakechroot fakeroot>. A