The daemon uses a priority list to automatically select the best-matching storage
driver for the backing filesystem that is used.
Historically, overlay2 was not supported on Btrfs and ZFS, and the daemon would
automatically pick the `btrfs` or `zfs` storage driver if that was the Backing
File System.
Commits 649e4c8889 and e226aea280
improved our detection to check if overlay2 was supported on the backing file-
system, allowing overlay2 to be used on top of Btrfs or ZFS, but did not change
the priority list.
While both Btrfs and ZFS have advantages for certain use-cases, and provide
advanced features that are not available to overlay2, they also are known
to require more "handholding", and are generally considered to be mostly
useful for "advanced" users.
This patch changes the storage-driver priority list, to prefer overlay2 (if
supported by the backing filesystem), and effectively makes btrfs and zfs
opt-in storage drivers.
This change does not affect existing installations; the daemon will detect
the storage driver that was previously in use (based on the presence of
storage directories in `/var/lib/docker`).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Switch to moby/sys/mount and mountinfo. Keep the pkg/mount for potential
outside users.
This commit was generated by the following bash script:
```
set -e -u -o pipefail
for file in $(git grep -l 'docker/docker/pkg/mount"' | grep -v ^pkg/mount); do
sed -i -e 's#/docker/docker/pkg/mount"#/moby/sys/mount"#' \
-e 's#mount\.\(GetMounts\|Mounted\|Info\|[A-Za-z]*Filter\)#mountinfo.\1#g' \
$file
goimports -w $file
done
```
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
`fuse-overlayfs` provides rootless overlayfs functionality without depending
on any kernel patch.
Aside from rootless, `fuse-overlayfs` could be potentially used for eliminating
`chown()` calls that happen in userns-remap mode, because `fuse-overlayfs` also
provides shiftfs functionality.
System requirements:
* fuse-overlayfs needs to be installed. Tested with 0.7.6.
* kernel >= 4.18
Unit test: `go test -exec sudo -v ./daemon/graphdriver/fuse-overlayfs`
The implementation is based on Podman's `overlay` driver which supports
both kernel-mode overlayfs and fuse-overlayfs in the single driver instance:
https://github.com/containers/storage/blob/39a8d5ed/drivers/overlay/overlay.go
However, Moby's implementation aims to decouple `fuse-overlayfs` driver from the
kernel-mode driver (`overlay2`) for simplicity.
Fix#40218
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
In case statfs() returns ENOENT, do not return an error, but rather
treat this as "not mounted".
Related to commit d42dbdd3d4.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Files that are suffixed with `_linux.go` or `_windows.go` are
already only built on Linux / Windows, so these build-tags
were redundant.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The fsmagic check was always performed on "data-root" (`/var/lib/docker`),
not on the storage-driver's home directory (e.g. `/var/lib/docker/<somedriver>`).
This caused detection to be done on the wrong filesystem in situations
where `/var/lib/docker/<somedriver>` was a mount, and a different
filesystem than `/var/lib/docker` itself.
This patch checks if the storage-driver's home directory exists, and only
falls back to `/var/lib/docker` if it doesn't exist.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Add a way to specify a custom graphdriver priority list
during build. This can be done with something like
go build -ldflags "-X github.com/docker/docker/daemon/graphdriver.priority=overlay2,devicemapper"
As ldflags are already used by the engine build process, and it seems
that only one (last) `-ldflags` argument is taken into account by go,
an envoronment variable `DOCKER_LDFLAGS` is introduced in order to
be able to append some text to `-ldflags`. With this in place,
using the feature becomes
make DOCKER_LDFLAGS="-X github.com/docker/docker/daemon/graphdriver.priority=overlay2,devicemapper" dynbinary
The idea behind this is, the priority list might be different
for different distros, so vendors are now able to change it
without patching the source code.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
It was causing the error message to be
'overlay' is not supported over <unknown>
instead of
'overlay' is not supported over ecryptfs
Signed-off-by: Iago López Galeiras <iago@kinvolk.io>
Changes most references of syscall to golang.org/x/sys/
Ones aren't changes include, Errno, Signal and SysProcAttr
as they haven't been implemented in /x/sys/.
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
[s390x] switch utsname from unsigned to signed
per 33267e036f
char in s390x in the /x/sys/unix package is now signed, so
change the buildtags
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
Now that overlay has matured, using
overlay is a better choice than devicemapper
on loopback devices.
This change promotes overlay in the
priority list. It also adds the
overlay2 graphdriver to the list
because overlay2 (if supported)
should be preferred over overlay.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
For things that we can check if they are mounted by using their fsmagic
we should use that and for others do it the slow way.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
Instead of implementing refcounts at each graphdriver, implement this in
the layer package which is what the engine actually interacts with now.
This means interacting directly with the graphdriver is no longer
explicitly safe with regard to Get/Put calls being refcounted.
In addition, with the containerd, layers may still be mounted after
a daemon restart since we will no longer explicitly kill containers when
we shutdown or startup engine.
Because of this ref counts would need to be repopulated.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Instead of implementing refcounts at each graphdriver, implement this in
the layer package which is what the engine actually interacts with now.
This means interacting directly with the graphdriver is no longer
explicitly safe with regard to Get/Put calls being refcounted.
In addition, with the containerd, layers may still be mounted after
a daemon restart since we will no longer explicitly kill containers when
we shutdown or startup engine.
Because of this ref counts would need to be repopulated.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Fixes#9960
This adds the output of a "Backing Filesystem:" entry to `docker info`
to overlay, aufs, and devicemapper graphdrivers. The default list
includes a fairly complete list of common filesystem names from
linux/include/uapi/linux/magic.h, but if the backing filesystem is not
recognized, the code will simply show "<unknown>"
Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>
Sebastiaan van Stijn