描述: 事实上，Docker 和 Containerd 是可以同时使用的，只不过 Docker 默认使用的 Containerd 的命名空间不是 default，而是 moby，此处为了更方便我们学习可以将 Docker 与 Containerd 联合使用。
Step 1.安装配置 containerd
yum install -y yum-utils
yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
yum makecache fast
yum -y install containerd.io
# cat /etc/containerd/config.toml
disabled_plugins = []
imports = []
oom_score = 0
plugin_dir = ""
required_plugins = []
root = "/var/lib/containerd"
state = "/run/containerd"
temp = ""
version = 2
[cgroup]
path = ""
[debug]
address = ""
format = ""
gid = 0
level = ""
uid = 0
[grpc]
address = "/run/containerd/containerd.sock"
gid = 0
max_recv_message_size = 16777216
max_send_message_size = 16777216
tcp_address = ""
tcp_tls_ca = ""
tcp_tls_cert = ""
tcp_tls_key = ""
uid = 0
[metrics]
address = ""
grpc_histogram = false
[plugins]
[plugins."io.containerd.gc.v1.scheduler"]
deletion_threshold = 0
mutation_threshold = 100
pause_threshold = 0.02
schedule_delay = "0s"
startup_delay = "100ms"
[plugins."io.containerd.grpc.v1.cri"]
device_ownership_from_security_context = false
disable_apparmor = false
disable_cgroup = false
disable_hugetlb_controller = true
disable_proc_mount = false
disable_tcp_service = true
enable_selinux = false
enable_tls_streaming = false
enable_unprivileged_icmp = false
enable_unprivileged_ports = false
ignore_image_defined_volumes = false
max_concurrent_downloads = 3
max_container_log_line_size = 16384
netns_mounts_under_state_dir = false
restrict_oom_score_adj = false
sandbox_image = "registry.cn-hangzhou.aliyuncs.com/google_containers/pause:3.6"
selinux_category_range = 1024
stats_collect_period = 10
stream_idle_timeout = "4h0m0s"
stream_server_address = "127.0.0.1"
stream_server_port = "0"
systemd_cgroup = false
tolerate_missing_hugetlb_controller = true
unset_seccomp_profile = ""
[plugins."io.containerd.grpc.v1.cri".cni]
bin_dir = "/opt/cni/bin"
conf_dir = "/etc/cni/net.d"
conf_template = ""
ip_pref = ""
max_conf_num = 1
[plugins."io.containerd.grpc.v1.cri".containerd]
default_runtime_name = "runc"
disable_snapshot_annotations = false
discard_unpacked_layers = false
ignore_rdt_not_enabled_errors = false
no_pivot = false
snapshotter = "stargz"
[plugins."io.containerd.grpc.v1.cri".containerd.default_runtime]
base_runtime_spec = ""
cni_conf_dir = ""
cni_max_conf_num = 0
container_annotations = []
pod_annotations = []
privileged_without_host_devices = false
runtime_engine = ""
runtime_path = ""
runtime_root = ""
runtime_type = ""
[plugins."io.containerd.grpc.v1.cri".containerd.default_runtime.options]
[plugins."io.containerd.grpc.v1.cri".containerd.runtimes]
[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc]
base_runtime_spec = ""
cni_conf_dir = ""
cni_max_conf_num = 0
container_annotations = []
pod_annotations = []
privileged_without_host_devices = false
runtime_engine = ""
runtime_path = ""
runtime_root = ""
runtime_type = "io.containerd.runc.v2"
[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]
BinaryName = ""
CriuImagePath = ""
CriuPath = ""
CriuWorkPath = ""
IoGid = 0
IoUid = 0
NoNewKeyring = false
NoPivotRoot = false
Root = ""
ShimCgroup = ""
SystemdCgroup = true
[plugins."io.containerd.grpc.v1.cri".containerd.untrusted_workload_runtime]
base_runtime_spec = ""
cni_conf_dir = ""
cni_max_conf_num = 0
container_annotations = []
pod_annotations = []
privileged_without_host_devices = false
runtime_engine = ""
runtime_path = ""
runtime_root = ""
runtime_type = ""
[plugins."io.containerd.grpc.v1.cri".containerd.untrusted_workload_runtime.options]
[plugins."io.containerd.grpc.v1.cri".image_decryption]
key_model = "node"
[plugins."io.containerd.grpc.v1.cri".registry]
config_path = ""
[plugins."io.containerd.grpc.v1.cri".registry.auths]
[plugins."io.containerd.grpc.v1.cri".registry.configs]
[plugins."io.containerd.grpc.v1.cri".registry.headers]
[plugins."io.containerd.grpc.v1.cri".registry.mirrors]
[plugins."io.containerd.grpc.v1.cri".registry.mirrors."docker.io"]
endpoint = ["https://docker.mirrors.ustc.edu.cn","http://hub-mirror.c.163.com"]
[plugins."io.containerd.grpc.v1.cri".registry.mirrors."gcr.io"]
endpoint = ["https://gcr.mirrors.ustc.edu.cn"]
[plugins."io.containerd.grpc.v1.cri".registry.mirrors."k8s.gcr.io"]
endpoint = ["https://gcr.mirrors.ustc.edu.cn/google-containers/"]
[plugins."io.containerd.grpc.v1.cri".registry.mirrors."quay.io"]
endpoint = ["https://quay.mirrors.ustc.edu.cn"]
[plugins."io.containerd.grpc.v1.cri".x509_key_pair_streaming]
tls_cert_file = ""
tls_key_file = ""
[plugins."io.containerd.internal.v1.opt"]
path = "/opt/containerd"
[plugins."io.containerd.internal.v1.restart"]
interval = "10s"
[plugins."io.containerd.internal.v1.tracing"]
sampling_ratio = 1.0
service_name = "containerd"
[plugins."io.containerd.metadata.v1.bolt"]
content_sharing_policy = "shared"
[plugins."io.containerd.monitor.v1.cgroups"]
no_prometheus = false
[plugins."io.containerd.runtime.v1.linux"]
no_shim = false
runtime = "runc"
runtime_root = ""
shim = "containerd-shim"
shim_debug = false
[plugins."io.containerd.runtime.v2.task"]
platforms = ["linux/amd64"]
sched_core = false
[plugins."io.containerd.service.v1.diff-service"]
default = ["walking"]
[plugins."io.containerd.service.v1.tasks-service"]
rdt_config_file = ""
[plugins."io.containerd.snapshotter.v1.aufs"]
root_path = ""
[plugins."io.containerd.snapshotter.v1.btrfs"]
root_path = ""
[plugins."io.containerd.snapshotter.v1.devmapper"]
async_remove = false
base_image_size = ""
discard_blocks = false
fs_options = ""
fs_type = ""
pool_name = ""
root_path = ""
[plugins."io.containerd.snapshotter.v1.native"]
root_path = ""
[plugins."io.containerd.snapshotter.v1.overlayfs"]
root_path = ""
upperdir_label = false
[plugins."io.containerd.snapshotter.v1.zfs"]
root_path = ""
[plugins."io.containerd.tracing.processor.v1.otlp"]
endpoint = ""
insecure = false
protocol = ""
[proxy_plugins]
[proxy_plugins.stargz]
type = "snapshot"
address = "/run/containerd-stargz-grpc/containerd-stargz-grpc.sock"
[stream_processors]
[stream_processors."io.containerd.ocicrypt.decoder.v1.tar"]
accepts = ["application/vnd.oci.image.layer.v1.tar+encrypted"]
args = ["--decryption-keys-path", "/etc/containerd/ocicrypt/keys"]
env = ["OCICRYPT_KEYPROVIDER_CONFIG=/etc/containerd/ocicrypt/ocicrypt_keyprovider.conf"]
path = "ctd-decoder"
returns = "application/vnd.oci.image.layer.v1.tar"
[stream_processors."io.containerd.ocicrypt.decoder.v1.tar.gzip"]
accepts = ["application/vnd.oci.image.layer.v1.tar+gzip+encrypted"]
args = ["--decryption-keys-path", "/etc/containerd/ocicrypt/keys"]
env = ["OCICRYPT_KEYPROVIDER_CONFIG=/etc/containerd/ocicrypt/ocicrypt_keyprovider.conf"]
path = "ctd-decoder"
returns = "application/vnd.oci.image.layer.v1.tar+gzip"
[timeouts]
"io.containerd.timeout.bolt.open" = "0s"
"io.containerd.timeout.shim.cleanup" = "5s"
"io.containerd.timeout.shim.load" = "5s"
"io.containerd.timeout.shim.shutdown" = "3s"
"io.containerd.timeout.task.state" = "2s"
[ttrpc]
address = ""
gid = 0
uid = 0
systemctl start containerd && systemctl enable containerd && systemctl status containerd
Step 2.在宿主机中安装docker客户端及服务
yum install -y yum-utils
yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
yum makecache fast
yum -y install docker-ce
tee /etc/docker/daemon.json <<-'EOF'
{
"live-restore": true,
"registry-mirrors": ["https://hub-mirror.c.163.com","https://bmtrgdvx.mirror.aliyuncs.com","https://y9lmbx5j.mirror.aliyuncs.com"],
"log-driver":"json-file",
"log-opts":{
"max-size" :"50m",
"max-file":"3"
}
}
EOF
Step 3.编辑/etc/systemd/system/multi-user.target.wants/docker.service文件并为其新增 --containerd如下启动项：--containerd /run/containerd/containerd.sock
vim /etc/systemd/system/multi-user.target.wants/docker.service
ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock --cri-containerd --debug
# - 重新加载配置
systemctl daemon-reload
systemctl enable docker && systemctl start docker && systemctl status docker
Step 4.打开两个Shell终端一个采用 docker 运行一个 busybox 容器，另外一个查看对比。
$ docker run --rm -it busybox sh
# / # ip addr
# 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
# link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
# inet 127.0.0.1/8 scope host lo
# valid_lft forever preferred_lft forever
# 8: eth0@if9: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
# link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff
# inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0 # 关键点
# valid_lft forever preferred_lft forever
# / # cat /etc/hosts
# 127.0.0.1 localhost
# 172.17.0.2 51dcdf68d3b8
# 采用 ctr 在 moby 名称空间下查看docker创建的容器以及Task PID
$ ctr -n moby c ls
# CONTAINER IMAGE RUNTIME
# 51dcdf68d3b8bf4c9707c9059e33f9570cb83725355595e77cf433dd3e25b64b - io.containerd.runc.v2
$ ctr -n moby t ls
# TASK PID STATUS
# 51dcdf68d3b8bf4c9707c9059e33f9570cb83725355595e77cf433dd3e25b64b 131926 RUNNING
# 验证获取到的 Task PID 下其 net 相关信息
$ grep "172.17.0.2" /proc/131926/net/fib_trie
|-- 172.17.0.2
|-- 172.17.0.2
# 采用 ctr 进入 Docker 创建的容器
$ ctr -n moby t exec -t --exec-id $RANDOM 51dcdf68d3b8bf4c9707c9059e33f9570cb83725355595e77cf433dd3e25b64b sh
# / # ip addr | grep "172.17.0.2"
# inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
# / # hostname
# 51dcdf68d3b8
Tips : containerd 引入了 namespace 概念, 每个image和container都会在各自的namespace下可见, 目前k8s会使用 k8s.io 以及 default 作为命名空间。
Tips : 当导入本地镜像时ctr不支持压缩。
Tips : 通过ctr containers create创建容器后，只是一个静态的容器，容器中的用户进程并没有启动，所以还需要通过ctr task start来启动容器进程。 当然也可以用ctr run的命令直接创建并运行容器。在进入容器操作时与docker不同的是，必须在ctr task exec命令后指定--exec-id参数，这个id可以随便写只要唯一就行。
Tips : ctr没有stop容器的功能，只能暂停（ctr task pause）或者杀死（ctr task kill）容器
