If you see similar errors as below when using openssl to test a https site, it is most likely caused by the SNI that is configured in the reverse proxy or server, like Nginx. openssl s_client -connect bla.bla.com:443 CONNECTED(00000003) 51089:error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol:/BuildRoot/Library/Caches/com.apple.xbs/Sources/OpenSSL098/OpenSSL098-59.60.1/src/ssl/s23_clnt.c:618: To make it work, you need to specify the hostname in the command, … Continue reading Openssl error: SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol
Tag: Linux
Find open ports from Linux kernel
Have you ever tried to find out the open ports in a Linux box without using the common tools like netstat, nmap, lsof, ss ... ? In some cases, the tools are just not available. e.g In a cutdown version Linux server or container, and you don't have the permission to install any software. I … Continue reading Find open ports from Linux kernel
Troubleshoot high CPU usage java process
This is a real troubleshooting example that I just did yesterday for a high CPU usage java application. The application uses tomcat and runs on AWS EC2. Login into the box, and change to root user so you can see all users' process. sudo su - Install htop if you have not installed it before, the run it. … Continue reading Troubleshoot high CPU usage java process
Autosam Release
Autosam is a project that I created to automate the Akamai Cloudlets Edge Redirect from end to end, including add new rules, remove duplicated rules if there are any, push to staging, test in staging, push to production, test in production. Now it is available for download from my Github repo. Enjoy Autosam 🙂
SSSD can not find some users in AD
We use SSSD to integrate RHEL7 into our Active Directory infrastructure for authentication. All users in the sys admins group can login with their AD credentials except one. It took me a few weeks to troubleshoot. On hand, I checked the sssd log and I can see the Linux server can find the user in … Continue reading SSSD can not find some users in AD
Jackie Chen's IT Workshop 