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Move root filesystem from rootfs to tmpfs #5133

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merged 4 commits into from
Aug 26, 2019
Merged

Move root filesystem from rootfs to tmpfs #5133

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edea8f9
Only use DOCKER_RAMDISK on fstype rootfs
afbjorklund Aug 14, 2019
a4c5992
Move root filesystem from rootfs to tmpfs
afbjorklund Aug 14, 2019
ae8894c
Stop using no_pivot when not using rootfs
afbjorklund Aug 14, 2019
eec1a06
Add warning that using --no-pivot is not secure
afbjorklund Aug 24, 2019
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2 changes: 1 addition & 1 deletion deploy/addons/gvisor/gvisor-config.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ oom_score = 0
max_container_log_line_size = 16384
[plugins.cri.containerd]
snapshotter = "overlayfs"
no_pivot = true
no_pivot = false
[plugins.cri.containerd.default_runtime]
runtime_type = "io.containerd.runtime.v1.linux"
runtime_engine = ""
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13 changes: 13 additions & 0 deletions deploy/iso/minikube-iso/board/coreos/minikube/rootfs-overlay/init
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@@ -0,0 +1,13 @@
#!/bin/sh
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For future archeologists, do you mind adding a quick comment describing why this file exists, and what it's intent is?

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future archeologists hahaha ! love it ! hello future archeologists from 2019 !

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Explaining init(1) ?

Or maybe what is the difference between this init and the normal one would be more appropriate. It doesn’t really help that the final /sbin/init is actually not init but just Lennart (systemd) posing

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I for one didn't realize this took the place of the system init, though it makes sense given the location.

It'd be nice to have an explanation of why data is being copied from one directory to another before exec'ing out to another init. =)

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Settled for adding a reference to switch_root(8)

DESCRIPTION
switch_root moves already mounted /proc, /dev, /sys and /run to newroot and makes newroot the new root filesystem and starts init process.

WARNING: switch_root removes recursively all files and directories on the current root filesystem.

mkdir /sysroot
# the value 90% borrowed from tcl via boot2docker
mount -t tmpfs -o size=90% tmpfs /sysroot
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Add a comment explaining how you arrived at 90% being the correct choice here.

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That’s easy, I stole it from tinycore (and boot2docker). 😀
I think it needs some space left, so using 100% won’t work. But we could probably get away with 95% since our VM is twice as big ? Can experiment with it

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That's fine. Just mention that you have copied the number from elsewhere then. I was afraid it might have some magical principle to it.

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I'll stick with 90%, until I know better. Will leave a reference to the original

# copy from rootfs, to be able to do switch_root(8)
tar -C / --exclude=sysroot -cf - . | tar -C /sysroot/ -xf -

# devtmpfs does not get automounted for initramfs
/bin/mount -t devtmpfs devtmpfs /sysroot/dev
exec 0</sysroot/dev/console
exec 1>/sysroot/dev/console
exec 2>/sysroot/dev/console
exec /sbin/switch_root /sysroot /sbin/init "$@"
2 changes: 1 addition & 1 deletion deploy/iso/minikube-iso/package/containerd-bin/config.toml
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Expand Up @@ -36,7 +36,7 @@ oom_score = 0
max_container_log_line_size = 16384
[plugins.cri.containerd]
snapshotter = "overlayfs"
no_pivot = true
no_pivot = false
[plugins.cri.containerd.default_runtime]
runtime_type = "io.containerd.runtime.v1.linux"
runtime_engine = ""
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2 changes: 1 addition & 1 deletion deploy/iso/minikube-iso/package/crio-bin/crio.conf
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Expand Up @@ -92,7 +92,7 @@ grpc_max_recv_msg_size = 16777216
default_runtime = "runc"

# If true, the runtime will not use pivot_root, but instead use MS_MOVE.
no_pivot = true
no_pivot = false

# Path to the conmon binary, used for monitoring the OCI runtime.
conmon = "/usr/libexec/crio/conmon"
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3 changes: 0 additions & 3 deletions deploy/iso/minikube-iso/package/podman/buildah.profile
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2 changes: 0 additions & 2 deletions deploy/iso/minikube-iso/package/podman/libpod.conf
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2 changes: 0 additions & 2 deletions deploy/iso/minikube-iso/package/podman/podman.mk
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Expand Up @@ -29,8 +29,6 @@ endef

define PODMAN_INSTALL_TARGET_CMDS
$(INSTALL) -Dm755 $(@D)/bin/podman $(TARGET_DIR)/usr/bin/podman
$(INSTALL) -Dm644 $(BR2_EXTERNAL_MINIKUBE_PATH)/package/podman/libpod.conf $(TARGET_DIR)/etc/containers/libpod.conf
$(INSTALL) -Dm644 $(BR2_EXTERNAL_MINIKUBE_PATH)/package/podman/buildah.profile $(TARGET_DIR)/etc/profile.d/podman.sh
endef

$(eval $(generic-package))
22 changes: 22 additions & 0 deletions pkg/provision/buildroot.go
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Expand Up @@ -92,6 +92,13 @@ func (p *BuildrootProvisioner) GenerateDockerOptions(dockerPort int) (*provision
driverNameLabel := fmt.Sprintf("provider=%s", p.Driver.DriverName())
p.EngineOptions.Labels = append(p.EngineOptions.Labels, driverNameLabel)

noPivot := true
// Using pivot_root is not supported on fstype rootfs
if fstype, err := rootFileSystemType(p); err == nil {
log.Debugf("root file system type: %s", fstype)
noPivot = fstype == "rootfs"
}
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engineConfigTmpl := `[Unit]
Description=Docker Application Container Engine
Documentation=https://docs.docker.com
Expand All @@ -101,8 +108,15 @@ Requires= minikube-automount.service docker.socket
[Service]
Type=notify

`
if noPivot {
log.Warn("Using fundamentally insecure --no-pivot option")
engineConfigTmpl += `
# DOCKER_RAMDISK disables pivot_root in Docker, using MS_MOVE instead.
Environment=DOCKER_RAMDISK=yes
`
}
engineConfigTmpl += `
{{range .EngineOptions.Env}}Environment={{.}}
{{end}}

Expand Down Expand Up @@ -160,6 +174,14 @@ WantedBy=multi-user.target
}, nil
}

func rootFileSystemType(p *BuildrootProvisioner) (string, error) {
fs, err := p.SSHCommand("df --output=fstype / | tail -n 1")
if err != nil {
return "", err
}
return strings.TrimSpace(fs), nil
}

// Package installs a package
func (p *BuildrootProvisioner) Package(name string, action pkgaction.PackageAction) error {
return nil
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