使用 etcdctl

etcdctl 是一个命令行客户端，它能提供一些简洁的命令，供用户直接跟 etcd 服务打交道，而无需基于 HTTP API 方式。这在某些情况下将很方便，例如用户对服务进行测试或者手动修改数据库内容。我们也推荐在刚接触 etcd 时通过 etcdctl 命令来熟悉相关的操作，这些操作跟 HTTP API 实际上是对应的。

etcd 项目二进制发行包中已经包含了 etcdctl 工具，没有的话，可以从 github.com/etcd-io/etcd/releases 下载。

etcdctl 支持如下的命令，大体上分为数据库操作和非数据库操作两类，后面将分别进行解释。

NAME:
    etcdctl - A simple command line client for etcd3.

USAGE:
    etcdctl

VERSION:
    3.4.0

API VERSION:
    3.4


COMMANDS:
    get            Gets the key or a range of keys
    put            Puts the given key into the store
    del            Removes the specified key or range of keys [key, range_end)
    txn            Txn processes all the requests in one transaction
    compaction        Compacts the event history in etcd
    alarm disarm        Disarms all alarms
    alarm list        Lists all alarms
    defrag            Defragments the storage of the etcd members with given endpoints
    endpoint health        Checks the healthiness of endpoints specified in `--endpoints` flag
    endpoint status        Prints out the status of endpoints specified in `--endpoints` flag
    watch            Watches events stream on keys or prefixes
    version            Prints the version of etcdctl
    lease grant        Creates leases
    lease revoke        Revokes leases
    lease timetolive    Get lease information
    lease keep-alive    Keeps leases alive (renew)
    member add        Adds a member into the cluster
    member remove        Removes a member from the cluster
    member update        Updates a member in the cluster
    member list        Lists all members in the cluster
    snapshot save        Stores an etcd node backend snapshot to a given file
    snapshot restore    Restores an etcd member snapshot to an etcd directory
    snapshot status        Gets backend snapshot status of a given file
    make-mirror        Makes a mirror at the destination etcd cluster
    migrate            Migrates keys in a v2 store to a mvcc store
    lock            Acquires a named lock
    elect            Observes and participates in leader election
    auth enable        Enables authentication
    auth disable        Disables authentication
    user add        Adds a new user
    user delete        Deletes a user
    user get        Gets detailed information of a user
    user list        Lists all users
    user passwd        Changes password of user
    user grant-role        Grants a role to a user
    user revoke-role    Revokes a role from a user
    role add        Adds a new role
    role delete        Deletes a role
    role get        Gets detailed information of a role
    role list        Lists all roles
    role grant-permission    Grants a key to a role
    role revoke-permission    Revokes a key from a role
    check perf        Check the performance of the etcd cluster
    help            Help about any command

OPTIONS:
      --cacert=""                verify certificates of TLS-enabled secure servers using this CA bundle
      --cert=""                    identify secure client using this TLS certificate file
      --command-timeout=5s            timeout for short running command (excluding dial timeout)
      --debug[=false]                enable client-side debug logging
      --dial-timeout=2s                dial timeout for client connections
      --endpoints=[127.0.0.1:2379]        gRPC endpoints
      --hex[=false]                print byte strings as hex encoded strings
      --insecure-skip-tls-verify[=false]    skip server certificate verification
      --insecure-transport[=true]        disable transport security for client connections
      --key=""                    identify secure client using this TLS key file
      --user=""                    username[:password] for authentication (prompt if password is not supplied)
  -w, --write-out="simple"            set the output format (fields, json, protobuf, simple, table)

数据库操作

数据库操作围绕对键值和目录的 CRUD （符合 REST 风格的一套操作：Create）完整生命周期的管理。

etcd 在键的组织上采用了层次化的空间结构（类似于文件系统中目录的概念），用户指定的键可以为单独的名字，如 testkey，此时实际上放在根目录 / 下面，也可以为指定目录结构，如 cluster1/node2/testkey，则将创建相应的目录结构。

注：CRUD 即 Create, Read, Update, Delete，是符合 REST 风格的一套 API 操作。

put

$ etcdctl put /testdir/testkey "Hello world"
OK

get

获取指定键的值。例如

$ etcdctl put testkey hello
OK
$ etcdctl get testkey
testkey
hello

支持的选项为

--sort 对结果进行排序

--consistent 将请求发给主节点，保证获取内容的一致性

del

删除某个键值。例如

$ etcdctl del testkey
1

非数据库操作

watch

监测一个键值的变化，一旦键值发生更新，就会输出最新的值。

例如，用户更新 testkey 键值为 Hello world。

$ etcdctl watch testkey
PUT
testkey
2

member

通过 list、add、update、remove 命令列出、添加、更新、删除 etcd 实例到 etcd 集群中。

例如本地启动一个 etcd 服务实例后，可以用如下命令进行查看。

$ etcdctl member list
422a74f03b622fef, started, node1, http://172.16.238.100:2380, http://172.16.238.100:23