Linux C API

Linux C APIreboot()；#include <linux/reboot.h>/* Definition of LINUX_REBOOT_* constants /#include <sys/syscall.h>/ Definition of SYS_* constants */#include <unistd.h>int syscall(SYS_r

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奔走在路上的小白 · 2021-11-29 15:41:57 发布

Linux C API

reboot()；
#include <linux/reboot.h> /* Definition of LINUX_REBOOT_* constants /
#include <sys/syscall.h> / Definition of SYS_* constants */
#include <unistd.h>

int syscall(SYS_reboot, int magic, int magic2, int cmd, void *arg);

/* Under glibc and most alternative libc's (including uclibc, dietlibc,
   musl and a few others), some of the constants involved have gotten
   symbolic names RB_*, and the library call is a 1-argument
   wrapper around the system call: */

#include <sys/reboot.h>    /* Definition of RB_* constants */
#include <unistd.h>

int reboot(int cmd);

DESCRIPTION top

   The reboot() call reboots the system, or enables/disables the
   reboot keystroke (abbreviated CAD, since the default is Ctrl-Alt-
   Delete; it can be changed using loadkeys(1)).

   This system call fails (with the error EINVAL) unless magic
   equals LINUX_REBOOT_MAGIC1 (that is, 0xfee1dead) and magic2
   equals LINUX_REBOOT_MAGIC2 (that is, 672274793).  However, since
   2.1.17 also LINUX_REBOOT_MAGIC2A (that is, 85072278) and since
   2.1.97 also LINUX_REBOOT_MAGIC2B (that is, 369367448) and since
   2.5.71 also LINUX_REBOOT_MAGIC2C (that is, 537993216) are
   permitted as values for magic2.  (The hexadecimal values of these
   constants are meaningful.)

   The cmd argument can have the following values:

   LINUX_REBOOT_CMD_CAD_OFF
          (RB_DISABLE_CAD, 0).  CAD is disabled.  This means that
          the CAD keystroke will cause a SIGINT signal to be sent to
          init (process 1), whereupon this process may decide upon a
          proper action (maybe: kill all processes, sync, reboot).

   LINUX_REBOOT_CMD_CAD_ON
          (RB_ENABLE_CAD, 0x89abcdef).  CAD is enabled.  This means
          that the CAD keystroke will immediately cause the action
          associated with LINUX_REBOOT_CMD_RESTART.

   LINUX_REBOOT_CMD_HALT
          (RB_HALT_SYSTEM, 0xcdef0123; since Linux 1.1.76).  The
          message "System halted." is printed, and the system is
          halted.  Control is given to the ROM monitor, if there is
          one.  If not preceded by a sync(2), data will be lost.

   LINUX_REBOOT_CMD_KEXEC
          (RB_KEXEC, 0x45584543, since Linux 2.6.13).  Execute a
          kernel that has been loaded earlier with kexec_load(2).
          This option is available only if the kernel was configured
          with CONFIG_KEXEC.

   LINUX_REBOOT_CMD_POWER_OFF
          (RB_POWER_OFF, 0x4321fedc; since Linux 2.1.30).  The
          message "Power down." is printed, the system is stopped,
          and all power is removed from the system, if possible.  If
          not preceded by a sync(2), data will be lost.

   LINUX_REBOOT_CMD_RESTART
          (RB_AUTOBOOT, 0x1234567).  The message "Restarting
          system." is printed, and a default restart is performed
          immediately.  If not preceded by a sync(2), data will be
          lost.

   LINUX_REBOOT_CMD_RESTART2
          (0xa1b2c3d4; since Linux 2.1.30).  The message "Restarting
          system with command '%s'" is printed, and a restart (using
          the command string given in arg) is performed immediately.
          If not preceded by a sync(2), data will be lost.

   LINUX_REBOOT_CMD_SW_SUSPEND
          (RB_SW_SUSPEND, 0xd000fce1; since Linux 2.5.18).  The
          system is suspended (hibernated) to disk.  This option is
          available only if the kernel was configured with
          CONFIG_HIBERNATION.

   Only the superuser may call reboot().

   The precise effect of the above actions depends on the
   architecture.  For the i386 architecture, the additional argument
   does not do anything at present (2.1.122), but the type of reboot
   can be determined by kernel command-line arguments ("reboot=...")
   to be either warm or cold, and either hard or through the BIOS.

Behavior inside PID namespaces
Since Linux 3.4, if reboot() is called from a PID namespace other
than the initial PID namespace with one of the cmd values listed
below, it performs a “reboot” of that namespace: the “init”
process of the PID namespace is immediately terminated, with the
effects described in pid_namespaces(7).

   The values that can be supplied in cmd when calling reboot() in
   this case are as follows:

   LINUX_REBOOT_CMD_RESTART, LINUX_REBOOT_CMD_RESTART2
          The "init" process is terminated, and wait(2) in the
          parent process reports that the child was killed with a
          SIGHUP signal.

   LINUX_REBOOT_CMD_POWER_OFF, LINUX_REBOOT_CMD_HALT
          The "init" process is terminated, and wait(2) in the
          parent process reports that the child was killed with a
          SIGINT signal.

   For the other cmd values, reboot() returns -1 and errno is set to
   EINVAL.

RETURN VALUE top

   For the values of cmd that stop or restart the system, a
   successful call to reboot() does not return.  For the other cmd
   values, zero is returned on success.  In all cases, -1 is
   returned on failure, and errno is set to indicate the error.

ERRORS top

   EFAULT Problem with getting user-space data under
          LINUX_REBOOT_CMD_RESTART2.

   EINVAL Bad magic numbers or cmd.

   EPERM  The calling process has insufficient privilege to call
          reboot(); the caller must have the CAP_SYS_BOOT inside its
          user namespace.