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Merge pull request #64665 from stealthybox/feature/kubeadm_845-systemd-resolved

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Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

kubeadm: Set the kubelet `--resolv-conf` flag conditionally on init

**What this PR does / why we need it**:
`kubeadm init` detects if systemd-resolved is running and configures the kubelet to use a working resolv.conf.
This patch also removes the warning message prompting manual user action for this configuration.

/area kubeadm
/area kubelet
/area dns
/kind bug
/priority important-soon

/sig cluster-lifecycle
/assign @timothysc

**Which issue(s) this PR fixes** 
Fixes https://github.com/kubernetes/kubeadm/issues/845

**Special notes for your reviewer**:
See the difference in `KUBELET_KUBEADM_ARGS` when running with this build and enabling the resolved daemon on Ubuntu 17.10:
```bash
root@vagrant:/vagrant/bin# bash << EOF
systemctl start systemd-resolved
./845_kubeadm init |& tail -n5
cat /var/lib/kubelet/kubeadm-flags.env

./845_kubeadm reset --force |& tail -n2
systemctl stop systemd-resolved
echo nameserver 8.8.8.8 > /etc/resolv.conf

./845_kubeadm init |& tail -n5
cat /var/lib/kubelet/kubeadm-flags.env

EOF
You can now join any number of machines by running the following on each node
as root:

  kubeadm join 10.0.2.15:6443 --token 77q84j.0342evur7rrfrwwx --discovery-token-ca-cert-hash sha256:190040f9c3adf8410bc6766dac79f8679870190564e15e8f8d1704fafa03f678

KUBELET_KUBEADM_ARGS=--cgroup-driver=cgroupfs --cni-bin-dir=/opt/cni/bin --cni-conf-dir=/etc/cni/net.d --network-plugin=cni --resolv-conf=/run/systemd/resolve/resolv.conf
I0603 06:49:16.592482   14106 reset.go:276] [reset] deleting contents of config directories: [/etc/kubernetes/manifests /etc/kubernetes/pki]
I0603 06:49:16.592858   14106 reset.go:290] [reset] deleting files: [/etc/kubernetes/admin.conf /etc/kubernetes/kubelet.conf /etc/kubernetes/bootstrap-kubelet.conf /etc/kubernetes/controller-manager.conf /etc/kubernetes/scheduler.conf]
You can now join any number of machines by running the following on each node
as root:

  kubeadm join 10.0.2.15:6443 --token 8mdart.gp67vq3nh9urq4z5 --discovery-token-ca-cert-hash sha256:da6b2e5841546eae134524b045e782f0dd91a6b53becc8d69c15d9eab9c88758

KUBELET_KUBEADM_ARGS=--cgroup-driver=cgroupfs --cni-bin-dir=/opt/cni/bin --cni-conf-dir=/etc/cni/net.d --network-plugin=cni
```

**Release note**:
```release-note
`kubeadm init` detects if systemd-resolved is running and configures the kubelet to use a working resolv.conf.
```
This commit is contained in:
Kubernetes Submit Queue 2018-06-04 08:20:31 -07:00 committed by GitHub
commit 86ae84b10e
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4 changed files with 8 additions and 32 deletions
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1
cmd/kubeadm/app/phases/kubelet/BUILD
View File

@ -19,6 +19,7 @@ go_library(
"//pkg/apis/rbac/v1:go_default_library",
"//pkg/kubelet/apis/kubeletconfig/scheme:go_default_library",
"//pkg/kubelet/apis/kubeletconfig/v1beta1:go_default_library",
"//pkg/util/procfs:go_default_library",
"//pkg/util/version:go_default_library",
"//vendor/github.com/golang/glog:go_default_library",
"//vendor/k8s.io/api/core/v1:go_default_library",

7
cmd/kubeadm/app/phases/kubelet/flags.go
View File

@ -28,6 +28,7 @@ import (
kubeadmapiv1alpha2 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha2"
"k8s.io/kubernetes/cmd/kubeadm/app/constants"
kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
"k8s.io/kubernetes/pkg/util/procfs"
utilsexec "k8s.io/utils/exec"
)
@ -72,8 +73,12 @@ func buildKubeletArgMap(nodeRegOpts *kubeadmapi.NodeRegistrationOptions, registe
kubeletFlags["register-with-taints"] = strings.Join(taintStrs, ",")
}
if pids, _ := procfs.PidOf("systemd-resolved"); len(pids) > 0 {
// procfs.PidOf only returns an error if the regex is empty or doesn't compile, so we can ignore it
kubeletFlags["resolv-conf"] = "/run/systemd/resolve/resolv.conf"
}
// TODO: Pass through --hostname-override if a custom name is used?
// TODO: Check if `systemd-resolved` is running, and set `--resolv-conf` based on that
// TODO: Conditionally set `--cgroup-driver` to either `systemd` or `cgroupfs` for CRI other than Docker
return kubeletFlags

1
cmd/kubeadm/app/preflight/BUILD
View File

@ -57,7 +57,6 @@ go_library(
"//pkg/registry/core/service/ipallocator:go_default_library",
"//pkg/util/initsystem:go_default_library",
"//pkg/util/ipvs:go_default_library",
"//pkg/util/procfs:go_default_library",
"//pkg/util/version:go_default_library",
"//pkg/version:go_default_library",
"//test/e2e_node/system:go_default_library",

31
cmd/kubeadm/app/preflight/checks.go
View File

@ -51,7 +51,6 @@ import (
"k8s.io/kubernetes/pkg/registry/core/service/ipallocator"
"k8s.io/kubernetes/pkg/util/initsystem"
ipvsutil "k8s.io/kubernetes/pkg/util/ipvs"
"k8s.io/kubernetes/pkg/util/procfs"
versionutil "k8s.io/kubernetes/pkg/util/version"
kubeadmversion "k8s.io/kubernetes/pkg/version"
"k8s.io/kubernetes/test/e2e_node/system"
@ -830,33 +829,6 @@ func getEtcdVersionResponse(client *http.Client, url string, target interface{})
return err
}
// ResolveCheck tests for potential issues related to the system resolver configuration
type ResolveCheck struct{}
// Name returns label for ResolveCheck
func (ResolveCheck) Name() string {
return "Resolve"
}
// Check validates the system resolver configuration
func (ResolveCheck) Check() (warnings, errors []error) {
glog.V(1).Infoln("validating the system resolver configuration")
warnings = []error{}
// procfs.PidOf only returns an error if the string passed is empty
// or there is an issue compiling the regex, so we can ignore it here
pids, _ := procfs.PidOf("systemd-resolved")
if len(pids) > 0 {
warnings = append(warnings, fmt.Errorf(
"systemd-resolved was detected, for cluster dns resolution to work "+
"properly --resolv-conf=/run/systemd/resolve/resolv.conf must be set "+
"for the kubelet. (/etc/systemd/system/kubelet.service.d/10-kubeadm.conf should be edited for this purpose)\n"))
}
return warnings, errors
}
// ImagePullCheck will pull container images used by kubeadm
type ImagePullCheck struct {
Images images.Images
@ -1011,8 +983,7 @@ func addCommonChecks(execer utilsexec.Interface, cfg kubeadmapi.CommonConfigurat
InPathCheck{executable: "ethtool", mandatory: false, exec: execer},
InPathCheck{executable: "socat", mandatory: false, exec: execer},
InPathCheck{executable: "tc", mandatory: false, exec: execer},
InPathCheck{executable: "touch", mandatory: false, exec: execer},
ResolveCheck{})
InPathCheck{executable: "touch", mandatory: false, exec: execer})
}
checks = append(checks,
SystemVerificationCheck{CRISocket: cfg.GetCRISocket()},