1.configmap的作用理解
configMap起什麼作用的呢？
舉個例子，啓用一個mysql容器。一般來說，mysql容器重要的有兩部分，一部分爲存儲數據，一部分爲配置文件my.cnf。
前面有測試過，存儲數據可以用pv pvc實現和容器的分離解耦。
配置文件也能夠實現和容器的分離解耦，也就是說mysql容器能夠直接讀取並使用預先配置好的配置文件（而不是使用容器中默認自帶的配置文件），非常方便。這就是configMap的功能。
kubernetes使用configMap來實現對容器中應用的配置文件管理。
2.創建configMap
創建ConfigMap的方式有兩種，一種是通過yaml文件來創建，另一種是通過kubectl直接在命令行下創建。
隨便找一個可用的配置好的my.cnf文件
現在測試，儘量簡單。
我的見下:
[root@kubernetes1 wp]# cat mysqld.cnf
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysql]
no-auto-rehash
[mysqld]
user = mysql
port = 3306
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
[mysqld_safe]
log-error= /var/log/mysql/mysql_oldboy.err
pid-file = /var/run/mysqld/mysqld.pid
[root@kubernetes1 wp]# 注意:
這個名字爲什麼是mysqld.cnf，是因爲容器裏讀取的配置文件名字就是這個，最少修改的原則，直接取代覆蓋，還用原名字。
用這個文件創建configmap
[root@kubernetes1 wp]# kubectl create configmap mysql-config --from-file=mysqld.cnf
configmap "mysql-config" created
[root@kubernetes1 wp]# kubectl describe configmap mysql-config
Name: mysql-config
Namespace: default
Labels: <none>
Annotations: <none>
Data
====
mysqld.cnf:
......3.以volume形式掛載進mysql容器，並讀取這個文件啓動
掛載在哪裏呢？
肯定是掛載到默認的存放配置文件處，並取代它。
mysql容器默認讀取的配置文件路徑見下:
root@mysql-5bbbf49b4f-wjw47:/etc/mysql# pwd
/etc/mysql
root@mysql-5bbbf49b4f-wjw47:/etc/mysql# ls
conf.d my.cnf my.cnf.fallback mysql.cnf mysql.conf.d
root@mysql-5bbbf49b4f-wjw47:/etc/mysql#my.cnf的內容見下:
root@mysql-7db74785b4-2mk4r:/etc/mysql# cat my.cnf
# Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
!includedir /etc/mysql/conf.d/
!includedir /etc/mysql/mysql.conf.d/分別看下這兩個目錄的內容
root@mysql-7db74785b4-2mk4r:/etc/mysql/mysql.conf.d# cat mysqld.cnf
# Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#
# The MySQL Server configuration file.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
[mysqld]
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
#log-error = /var/log/mysql/error.log
# By default we only accept connections from localhost
#bind-address = 127.0.0.1
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
root@mysql-7db74785b4-2mk4r:/etc/mysql/mysql.conf.d# 可以看到最重要的配置文件就是這個，configmap掛載到這裏，用我們預設的配置文件取代這裏的mysqld.cnf
這裏的路徑是:
root@mysql-7db74785b4-2mk4r:/etc/mysql/mysql.conf.d# pwd
/etc/mysql/mysql.conf.d
root@mysql-7db74785b4-2mk4r:/etc/mysql/mysql.conf.d# ls
mysqld.cnf以下是service和pod的配置文件:
[root@kubernetes1 wp]# cat mysql-svc2.yml
apiVersion: v1
kind: Service
metadata:
name: mysql2
spec:
ports:
- port: 3306
selector:
app: mysql1
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
name: mysql-t1
spec:
selector:
matchLabels:
app: mysql1
template:
metadata:
labels:
app: mysql1
spec:
containers:
- image: mysql:5.7
name: mysql-t
env:
- name: MYSQL_ROOT_PASSWORD
valueFrom:
secretKeyRef:
name: mysecret
key: password
ports:
- containerPort: 3306
name: mysql
volumeMounts:
- name: mysql-t1
mountPath: /etc/mysql/mysql.conf.d ##注意路徑
volumes:
- name: mysql-t1
configMap:
name: mysql-config[root@kubernetes1 wp]# kubectl apply -f mysql-svc2.yml
service "mysql2" created
deployment.apps "mysql-t1" created起來了
[root@kubernetes1 wp]# kubectl get pod -owide
NAME READY STATUS RESTARTS AGE IP NODE
httpd-749bf8c6f4-bfjfw 1/1 Running 1 5d 10.244.2.4 kubernetes3
httpd-749bf8c6f4-ghpzl 1/1 Running 1 5d 10.244.2.5 kubernetes3
httpd-749bf8c6f4-xvrn4 1/1 Running 1 5d 10.244.2.253 kubernetes3
mysql-7db74785b4-2mk4r 1/1 Running 0 1h 10.244.1.29 kubernetes2
mysql-t1-6fbf57db97-z5rtl 1/1 Running 0 13s 10.244.1.36 kubernetes2
nginx-deployment-6b5c99b6fd-pscr6 1/1 Running 1 5d 10.244.1.27 kubernetes2
nginx-deployment-6b5c99b6fd-zr2p7 1/1 Running 1 5d 10.244.2.254 kubernetes3
node-exporter-4gbh9 1/1 Running 25 41d 192.168.211.152 kubernetes3
node-exporter-8h9vp 1/1 Running 26 41d 192.168.211.151 kubernetes2
wordpress-pod-7dd7659959-hc7mr 1/1 Running 5 8d 10.244.2.2 kubernetes3
[root@kubernetes1 wp]# 進入容器檢查是不是讀取到了我們的配置文件
[root@kubernetes2 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c78f97476162 66bc0f66b7af "docker-entrypoint..." About a minute ago Up About a minute k8s_mysql-t_mysql-t1-6fbf57db97-z5rtl_default_72eeb07c-9a27-11e8-8e76-000c292f3b91_0root@mysql-t1-6fbf57db97-z5rtl:/etc/mysql/mysql.conf.d# ls
mysqld.cnf
root@mysql-t1-6fbf57db97-z5rtl:/etc/mysql/mysql.conf.d# cat mysqld.cnf
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysql]
no-auto-rehash
[mysqld]
user = mysql
port = 3306
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
[mysqld_safe]
log-error= /var/log/mysql/mysql_oldboy.err
pid-file = /var/run/mysqld/mysqld.pid可以看到已經覆蓋原文件。
root@mysql-t1-6fbf57db97-z5rtl:/var/log/mysql# ls
error.log
root@mysql-t1-6fbf57db97-z5rtl:/var/log/mysql# cat error.log
2018-06-26T23:03:23.234767Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2018-06-26T23:03:23.525795Z 0 [Warning] InnoDB: New log files created, LSN=45790日誌也已經根據配置文件生成。
測試成功。
4.思路總結
其實並不難，主要是要找配置文件的存放目錄，然後用volume掛載配置好的configmap文件到配置文件的目錄，取代默認的配置文件即可。
需要注意的是configmap讀取的文件名需和默認的配置文件名相同。