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Shell Programming and Scripting
Cleaning Message Queues
Post 302529496 by Corona688 on Thursday 9th of June 2011 11:57:37 AM
06-09-2011
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#include <sys/ipc.h>
#include <sys/msg.h>
int main()
{
int qid;
int t;
struct msgbuf mesg;
qid=msgget(IPC_PRIVATE,IPC_CREAT);
mesg.mtype=1L;
mesg.mtext=1;
t=msgsnd(qid,&mesg,1,0);
printf("%d",t);
}
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LEARN ABOUT CENTOS
dracut-shutdown.service
DRACUT-SHUTDOWN.S(8) dracut DRACUT-SHUTDOWN.S(8) NAME
dracut-shutdown.service - unpack the initramfs to /run/initramfs SYNOPSIS
dracut-shutdown.service DESCRIPTION
This service unpacks the initramfs image to /run/initramfs. systemd pivots into /run/initramfs at shutdown, so the root filesytem can be safely unmounted. The following steps are executed during a shutdown: o systemd switches to the shutdown.target o systemd starts /lib/systemd/system/shutdown.target.wants/dracut-shutdown.service o dracut-shutdown.service executes /usr/lib/dracut/dracut-initramfs-restore which unpacks the initramfs to /run/initramfs o systemd finishes shutdown.target o systemd kills all processes o systemd tries to unmount everything and mounts the remaining read-only o systemd checks, if there is a /run/initramfs/shutdown executable o if yes, it does a pivot_root to /run/initramfs and executes ./shutdown. The old root is then mounted on /oldroot. /usr/lib/dracut/modules.d/99shutdown/shutdown.sh is the shutdown executable. o shutdown will try to umount every /oldroot mount and calls the various shutdown hooks from the dracut modules This ensures, that all devices are disassembled and unmounted cleanly. To debug the shutdown process, you can get a shell in the shutdown procedure by injecting "rd.break=pre-shutdown rd.shell" or "rd.break=shutdown rd.shell". # mkdir -p /run/initramfs/etc/cmdline.d # echo "rd.break=pre-shutdown rd.shell" > /run/initramfs/etc/cmdline.d/debug.conf # touch /run/initramfs/.need_shutdown AUTHORS
Harald Hoyer SEE ALSO
dracut(8) dracut 09/12/2013 DRACUT-SHUTDOWN.S(8)