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sd-shutdown.h
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ #ifndef foosdshutdownhfoo #define foosdshutdownhfoo /*** This file is part of systemd. Copyright 2010 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. ***/ /* Interface for scheduling and cancelling timed shutdowns. */ #include <inttypes.h> #ifdef __cplusplus extern "C" { #endif #ifndef _sd_packed_ # define _sd_packed_ __attribute__((packed)) #endif typedef enum sd_shutdown_mode { SD_SHUTDOWN_NONE = 0, SD_SHUTDOWN_REBOOT = 'r', SD_SHUTDOWN_POWEROFF = 'P', SD_SHUTDOWN_HALT = 'H', SD_SHUTDOWN_KEXEC = 'K' } sd_shutdown_mode_t; /* Calculate the size of the message as "offsetof(struct * sd_shutdown_command, wall_message) + * strlen(command.wall_message)" */ struct sd_shutdown_command { /* Microseconds after the epoch 1970 UTC */ uint64_t usec; /* H, P, r, i.e. the switches usually passed to * /usr/bin/shutdown to select whether to halt, power-off or * reboot the machine */ sd_shutdown_mode_t mode:8; /* If non-zero, don't actually shut down, just pretend */ unsigned dry_run:1; /* If non-zero, send our wall message */ unsigned warn_wall:1; /* The wall message to send around. Leave empty for the * default wall message */ char wall_message[]; } _sd_packed_; /* The scheme is very simple: * * To schedule a shutdown, simply fill in and send a single * AF_UNIX/SOCK_DGRAM datagram with the structure above suffixed with * the wall message to the socket /run/systemd/shutdownd (leave an * empty wall message for the default shutdown message). To calculate * the size of the message, use "offsetof(struct sd_shutdown_command, * wall_message) + strlen(command.wall_message)". * * To cancel a shutdown, do the same, but send a fully zeroed-out * structure. * * To be notified about scheduled shutdowns, create an inotify watch * on /run/shutdown/. Whenever a file called "scheduled" appears, a * shutdown is scheduled. If it is removed, it is canceled. If it is * replaced, the scheduled shutdown has been changed. The file contains * a simple, environment-like block that contains information about * the scheduled shutdown: * * USEC= * encodes the time for the shutdown in usecs since the epoch UTC, * formatted as a numeric string. * * WARN_WALL= * is 1 if a wall message shall be sent * * DRY_RUN= * is 1 if a dry-run shutdown is scheduled * * MODE= * is the shutdown mode, one of "poweroff", "reboot", "halt", "kexec" * * WALL_MESSAGE= * is the wall message to use, with all special characters escaped in C-style. * * Note that some fields might be missing if they do not apply. * * Note that the file is first written to a temporary file and then * renamed, in order to provide atomic properties for readers: if the * file exists under the name "scheduled", it is guaranteed to be fully * written. A reader should ignore all files in that directory by any * other name. * * Scheduled shutdowns are only accepted from privileged processes, * but anyone may watch the directory and the file in it. */ #ifdef __cplusplus } #endif #endif