Public bug reported:
SRU Justification
Impact: Currently it is not possible to use overlayfs on top of shiftfs.
This means Docker inside of LXD cannot make user of the overlay2 graph
driver which is blocking users such as Travis from making use of it
efficiently.
Regression Potential: Limited to shiftfs and overlayfs on top of
shiftfs. Overlayfs does prevent "remote" filesystems such as ceph, nfs,
etc. from being used as the underlay. With this patch shiftfs however
can be used as an underlay and we special case it as a suitable
filesystem to be used under overlayfs. I verified that the patch does
not lead to regression on overlayfs workloads that do not make use of
shiftfs as underlay. Additionally, I tested Docker with the overlay2
graphdriver on top of shiftfs. This also has not lead to any
regressions.
Test case: Building a kernel with the patch:
sudo snap install lxd
sudo lxd init
sudo lxc launch images:ubuntu/bionic b1
sudo lxc config set b1 security.nesting true
sudo lxc restart --force b1
sudo lxc shell b1
sudo apt-get install \
apt-transport-https \
ca-certificates \
curl \
gnupg-agent \
software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
curl -fsSL get.docker.com | CHANNEL=test sh
sudo add-apt-repository \
"deb [arch=amd64] https://download.docker.com/linux/ubuntu \
$(lsb_release -cs) \
stable"
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io
sudo systemctl stop docker
cat <<EOF /etc/docker/daemon.json
{
"storage-driver": "overlay2"
}
EOF
sudo systemctl start docker
docker run -it ubuntu bash
and observe that it works.
Target kernels: All LTS kernels that do support shiftfs, if possible.
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Christian Brauner (cbrauner)
Status: In Progress
** Changed in: linux (Ubuntu)
Assignee: (unassigned) => Christian Brauner (cbrauner)
** Changed in: linux (Ubuntu)
Status: New => Confirmed
** Changed in: linux (Ubuntu)
Status: Confirmed => In Progress
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https://bugs.launchpad.net/bugs/1838677
Title:
shiftfs: allow overlayfs
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