Operation and maintenance failure experience sharing

Student case 1：

notice Install the database to /data/mysql Catalog There is a mess beside the direction mysql5.89 A jumble of papers , You think it's useless direct rm -rf Delete , It's refreshing now ,, For a while If you find any business, you must log in and report an error 500 Unable to connect to database ？ Why? You dried up the database ！ The database was deleted I don't know why ？ All accounts are owed by the foundation , Therefore, operation and maintenance must have a solid foundation .

Student case 2：

At the beginning, I studied Linux Use , From foundation to service to cluster , It's all done in virtual machines , Although I told us that it was no different from the real machine , But the desire for the real world is growing , However, various snapshots of virtual machines let us form a variety of cheap habits , So that when I get the server operation permission , Can't wait to try , Remember the first day at work , Boss root Give me the code , Because you can only use xshell, I just want to use xshell, So quietly log in to the server and try to change it to xshell+ Key login , Because there's no test , There is no one left ssh Connect , All reboots sshd After the server , I'm blocked from the server , Fortunately, I backed up sshd_config file , Later let the computer room staff cp In the past , Fortunately this is a small company , Or I'll be done directly …… Good luck