disable talkback mode

Modify the Startup Mode of ubuntu 14 and disable the graphic interface for startup. The default runlevel of Ubuntu is 2. You can use runlevel to view the current default running level. The runlevel is defined as follows: 0-Halt, shutdown mode 1-Single, Single user mode 2-Full multi-user with display manager (GUI) 3-F

Linux: CentOS 5.5 Enhance system security by adding a password to the grub boot loader, so as to disable the single-user mode and prevent malicious modification of the root password by logging on to the single-user mode, you only need to modify the configuration file of grub to encrypt grub. 1. Enter the system as the root user 2. Enter the grub-md5-crypt in t

There are two waysThe first, throws an exception inside Init, defines the private init-(Instancetype) init {[Self doesnotrecognizeselector:_cmd]; return nil;}-(Instancetype) initprivate {self = [super init]; if (self) {} return to self;}+ (Instancetype) sharedinstance {static Mysingleton *sharedinstance;Static dispatch_once_t Oncetoken;Dispatch_once (oncetoken, ^{sharedinstance = [[Self alloc] initprivate];}); return sharedinstance;}Second, directly returning a singleton in Init-(Instancetype) i