This Jenkins instance appears to be offline

青春须早为，岂能长少年。这篇文章主要讲述This Jenkins instance appears to be offline相关的知识，希望能为你提供帮助。
tomcat 方式启动jenkins时，报：This Jenkins instance appears to be offline and offers options to "Configure Proxy" or "Skip Plugin Installation"
网上有个帖子：
In my case, it has something to do with SSL. I manage to fix it by editing `/var/lib/jenkins/hudson.model.UpdateCenter.xml` and change url to use `http` instead of `https`.
Restart jenkins and reload the website, it no longer shows offline.

[[email protected] jenkins]# find / -name "hudson.model.UpdateCenter.xml" /work/data/jenkins/hudson.model.UpdateCenter.xml

< ?xml version=‘1.0‘ encoding=‘UTF-8‘?> < sites> < site> < id> default< /id> < url> https://updates.jenkins.io/update-center.json< /url> < /site> < /sites>

在jenkins服务器直接 wget https://updates.jenkins.io/update-center.json

[[email protected] jenkins]# wget https://updates.jenkins.io/update-center.json --2017-09-19 12:35:45--https://updates.jenkins.io/update-center.json Resolving updates.jenkins.io... 52.202.51.185 Connecting to updates.jenkins.io|52.202.51.185|:443... connected. ERROR: certificate common name “pkg.jenkins.io” doesn’t match requested host name “updates.jenkins.io”. To connect to updates.jenkins.io insecurely, use ‘--no-check-certificate’.

wget http://updates.jenkins.io/update-center.json

[[email protected] jenkins]# wget http://updates.jenkins.io/update-center.json --2017-09-19 12:36:30--http://updates.jenkins.io/update-center.json Resolving updates.jenkins.io... 52.202.51.185 Connecting to updates.jenkins.io|52.202.51.185|:80... connected. HTTP request sent, awaiting response... 301 Moved Permanently Location: http://updates.jenkins.io/current/update-center.json [following] --2017-09-19 12:36:30--http://updates.jenkins.io/current/update-center.json Reusing existing connection to updates.jenkins.io:80. HTTP request sent, awaiting response... 302 Found Location: http://mirrors.jenkins-ci.org/updates/current/update-center.json [following] --2017-09-19 12:36:31--http://mirrors.jenkins-ci.org/updates/current/update-center.json Resolving mirrors.jenkins-ci.org... 52.202.51.185 Reusing existing connection to updates.jenkins.io:80. HTTP request sent, awaiting response... 302 Found Location: http://mirrors.tuna.tsinghua.edu.cn/jenkins/updates/current/update-center.json [following] --2017-09-19 12:36:31--http://mirrors.tuna.tsinghua.edu.cn/jenkins/updates/current/update-center.json Resolving mirrors.tuna.tsinghua.edu.cn... 101.6.6.178, 2402:f000:1:416:101:6:6:177 Connecting to mirrors.tuna.tsinghua.edu.cn|101.6.6.178|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 1229441 (1.2M) [application/json] Saving to: “update-center.json”100%[=====================================================================================================================================================> ] 1,229,4412.43M/sin 0.5s2017-09-19 12:36:32 (2.43 MB/s) - “update-center.json” saved [1229441/1229441]

【This Jenkins instance appears to be offline】确实是因为https的问题，把它修改成http，重启jenkins就OK了