From ff98da0607c4d6a94a2356d9ccaa64cc9d7f6a78 Mon Sep 17 00:00:00 2001 From: Derek McGowan Date: Mon, 11 Jul 2016 16:48:08 -0700 Subject: [PATCH] Allow option to override kernel check in overlay2 Add option to skip kernel check for older kernels which have been patched to support multiple lower directories in overlayfs. Fixes #24023 Signed-off-by: Derek McGowan (github: dmcgowan) --- daemon/graphdriver/overlay2/overlay.go | 36 +++++++++++++++++++++++++- docs/reference/commandline/dockerd.md | 11 ++++++++ 2 files changed, 46 insertions(+), 1 deletion(-) diff --git a/daemon/graphdriver/overlay2/overlay.go b/daemon/graphdriver/overlay2/overlay.go index b48bcb90de..136d058d5d 100644 --- a/daemon/graphdriver/overlay2/overlay.go +++ b/daemon/graphdriver/overlay2/overlay.go @@ -10,6 +10,7 @@ import ( "os" "os/exec" "path" + "strconv" "strings" "syscall" @@ -21,6 +22,7 @@ import ( "github.com/docker/docker/pkg/directory" "github.com/docker/docker/pkg/idtools" "github.com/docker/docker/pkg/mount" + "github.com/docker/docker/pkg/parsers" "github.com/docker/docker/pkg/parsers/kernel" "github.com/opencontainers/runc/libcontainer/label" @@ -92,6 +94,10 @@ func init() { // If overlay filesystem is not supported on the host, graphdriver.ErrNotSupported is returned as error. // If a overlay filesystem is not supported over a existing filesystem then error graphdriver.ErrIncompatibleFS is returned. func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error) { + opts, err := parseOptions(options) + if err != nil { + return nil, err + } if err := supportsOverlay(); err != nil { return nil, graphdriver.ErrNotSupported @@ -103,7 +109,10 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap return nil, err } if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: 4, Major: 0, Minor: 0}) < 0 { - return nil, graphdriver.ErrNotSupported + if !opts.overrideKernelCheck { + return nil, graphdriver.ErrNotSupported + } + logrus.Warnf("Using pre-4.0.0 kernel for overlay2, mount failures may require kernel update") } fsMagic, err := graphdriver.GetFSMagic(home) @@ -144,6 +153,31 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap return d, nil } +type overlayOptions struct { + overrideKernelCheck bool +} + +func parseOptions(options []string) (*overlayOptions, error) { + o := &overlayOptions{} + for _, option := range options { + key, val, err := parsers.ParseKeyValueOpt(option) + if err != nil { + return nil, err + } + key = strings.ToLower(key) + switch key { + case "overlay2.override_kernel_check": + o.overrideKernelCheck, err = strconv.ParseBool(val) + if err != nil { + return nil, err + } + default: + return nil, fmt.Errorf("overlay2: Unknown option %s\n", key) + } + } + return o, nil +} + func supportsOverlay() error { // We can try to modprobe overlay first before looking at // proc/filesystems for when overlay is supported diff --git a/docs/reference/commandline/dockerd.md b/docs/reference/commandline/dockerd.md index a881b62ac6..8c53fd02c3 100644 --- a/docs/reference/commandline/dockerd.md +++ b/docs/reference/commandline/dockerd.md @@ -566,6 +566,17 @@ options for `zfs` start with `zfs` and options for `btrfs` start with `btrfs`. Example use: $ docker daemon -s btrfs --storage-opt btrfs.min_space=10G +#### Overlay2 options + +* `overlay2.override_kernel_check` + + Overrides the Linux kernel version check allowing overlay2. Support for + specifying multiple lower directories needed by overlay2 was added to the + Linux kernel in 4.0.0. However some older kernel versions may be patched + to add multiple lower directory support for OverlayFS. This option should + only be used after verifying this support exists in the kernel. Applying + this option on a kernel without this support will cause failures on mount. + ## Docker runtime execution options The Docker daemon relies on a