How does Linux operating system shut down? [on hold]
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Gilles wrote an excellent reply about how Linux kernel shuts down at https://unix.stackexchange.com/a/122667/674
I was wondering how Linux OS shuts down (in cases of both systemvinit and systemd)? I am expecting something similar to the boot sequence of Linux OS.
I am particularly wondering how the processes notify each other, by some signal like SIGTERM and SIGKILL, or some other interprocess communication way?
Thanks.
Related:
What is the difference between "when the operating system shuts down" and "when the kernel shuts down"?
When the operating system shuts down, how does a service manager know that it should sends SIGTERM and SIGKILL to its services?
linux systemd shutdown init
edited 9 hours ago
Jeff Schaller
38.1k1053124
asked yesterday
Tim
25.5k74245449
put on hold as too broad by Scott, Mr Shunz, RalfFriedl, DarkHeart, Stephen Harris 1 hour ago
Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
add a comment |
up vote
-3
down vote
favorite
Gilles wrote an excellent reply about how Linux kernel shuts down at https://unix.stackexchange.com/a/122667/674
I was wondering how Linux OS shuts down (in cases of both systemvinit and systemd)? I am expecting something similar to the boot sequence of Linux OS.
I am particularly wondering how the processes notify each other, by some signal like SIGTERM and SIGKILL, or some other interprocess communication way?
Thanks.
Related:
What is the difference between "when the operating system shuts down" and "when the kernel shuts down"?
When the operating system shuts down, how does a service manager know that it should sends SIGTERM and SIGKILL to its services?
linux systemd shutdown init
edited 9 hours ago
Jeff Schaller
38.1k1053124
asked yesterday
Tim
25.5k74245449
put on hold as too broad by Scott, Mr Shunz, RalfFriedl, DarkHeart, Stephen Harris 1 hour ago
Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
Maybe at a high level with only critical parts?
– Tim
yesterday
Don't be afraid. Since you mentioned it, I would refrain myself from doing so.
– Tim
yesterday
add a comment |
up vote
-3
down vote
favorite
up vote
-3
down vote
favorite
Gilles wrote an excellent reply about how Linux kernel shuts down at https://unix.stackexchange.com/a/122667/674
I was wondering how Linux OS shuts down (in cases of both systemvinit and systemd)? I am expecting something similar to the boot sequence of Linux OS.
I am particularly wondering how the processes notify each other, by some signal like SIGTERM and SIGKILL, or some other interprocess communication way?
Thanks.
Related:
What is the difference between "when the operating system shuts down" and "when the kernel shuts down"?
When the operating system shuts down, how does a service manager know that it should sends SIGTERM and SIGKILL to its services?
linux systemd shutdown init
edited 9 hours ago
Jeff Schaller
38.1k1053124
asked yesterday
Tim
25.5k74245449
Gilles wrote an excellent reply about how Linux kernel shuts down at https://unix.stackexchange.com/a/122667/674
I was wondering how Linux OS shuts down (in cases of both systemvinit and systemd)? I am expecting something similar to the boot sequence of Linux OS.
I am particularly wondering how the processes notify each other, by some signal like SIGTERM and SIGKILL, or some other interprocess communication way?
Thanks.
Related:
What is the difference between "when the operating system shuts down" and "when the kernel shuts down"?
When the operating system shuts down, how does a service manager know that it should sends SIGTERM and SIGKILL to its services?
linux systemd shutdown init
linux systemd shutdown init
edited 9 hours ago
Jeff Schaller
38.1k1053124
asked yesterday
Tim
25.5k74245449
edited 9 hours ago
Jeff Schaller
38.1k1053124
asked yesterday
Tim
25.5k74245449
edited 9 hours ago
Jeff Schaller
38.1k1053124
edited 9 hours ago
Jeff Schaller
38.1k1053124
edited 9 hours ago
Jeff Schaller
38.1k1053124
38.1k1053124
asked yesterday
Tim
25.5k74245449
asked yesterday
Tim
25.5k74245449
asked yesterday
Tim
25.5k74245449
25.5k74245449
put on hold as too broad by Scott, Mr Shunz, RalfFriedl, DarkHeart, Stephen Harris 1 hour ago
Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
put on hold as too broad by Scott, Mr Shunz, RalfFriedl, DarkHeart, Stephen Harris 1 hour ago
Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
Maybe at a high level with only critical parts?
– Tim
yesterday
Don't be afraid. Since you mentioned it, I would refrain myself from doing so.
– Tim
yesterday
add a comment |
Maybe at a high level with only critical parts?
– Tim
yesterday
Don't be afraid. Since you mentioned it, I would refrain myself from doing so.
– Tim
yesterday
Maybe at a high level with only critical parts?
– Tim
yesterday
Maybe at a high level with only critical parts?
– Tim
yesterday
Don't be afraid. Since you mentioned it, I would refrain myself from doing so.
– Tim
yesterday
Don't be afraid. Since you mentioned it, I would refrain myself from doing so.
– Tim
yesterday
add a comment |
1 Answer
1
active
oldest
votes
up vote
3
down vote
accepted
With both sysvinit and systemd, shutting the operating system down starts by notifying the init process (the process with pid 1) that the system should shut down (or reboot, or power off).
sysvinit does this by using the /run/initctl FIFO to communicate with init, asking it to switch to the corresponding runlevel. See the init manpage for a brief overview.
systemd supports a variety of ways to do this. Various signals can be used to request a shutdown, reboot, etc., in various flavours; it’s also possible to request this over d-bus (the busctl manpage explains how to explore that).
Once pid 1 has been asked to shut down, it follows its configuration and specification and goes through all the appropriate steps for it. This typically includes notifying all users that a shutdown is in progress, shutting down all the running services (in a managed way with systemd; using shutdown scripts in various forms with sysvinit), syncing the mounted file systems, possibly unmounting them, killing all remaining processes (with the usual TERM then KILL sequence), and finally calling the kernel’s reboot system call with the appropriate parameters.
This describes the general sequence. There are many more twists to all this, including access control (with Polkit), various available hooks, kexec, sudden power-off handling, CtrlAltDel handling... The systemd documentation covers many of these details.
answered yesterday
Stephen Kitt
162k24362440
Thanks. In manpages.debian.org/stretch/sysvinit-core/…,initalso reacts to some signals. Does that mean we can communicate withinitby sending some signals instead of using FIFO, asking it to switch to the corresponding runlevel?
– Tim
23 hours ago
/run/initctlis FIFO not socket. Let me know if I am wrong.
– Tim
22 hours ago
You can use certain signals to communicate withsysvinit’sinit, but none of them are relevant here. You can’t use them to request an arbitrary runlevel change.
– Stephen Kitt
20 hours ago
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
accepted
With both sysvinit and systemd, shutting the operating system down starts by notifying the init process (the process with pid 1) that the system should shut down (or reboot, or power off).
sysvinit does this by using the /run/initctl FIFO to communicate with init, asking it to switch to the corresponding runlevel. See the init manpage for a brief overview.
systemd supports a variety of ways to do this. Various signals can be used to request a shutdown, reboot, etc., in various flavours; it’s also possible to request this over d-bus (the busctl manpage explains how to explore that).
Once pid 1 has been asked to shut down, it follows its configuration and specification and goes through all the appropriate steps for it. This typically includes notifying all users that a shutdown is in progress, shutting down all the running services (in a managed way with systemd; using shutdown scripts in various forms with sysvinit), syncing the mounted file systems, possibly unmounting them, killing all remaining processes (with the usual TERM then KILL sequence), and finally calling the kernel’s reboot system call with the appropriate parameters.
This describes the general sequence. There are many more twists to all this, including access control (with Polkit), various available hooks, kexec, sudden power-off handling, CtrlAltDel handling... The systemd documentation covers many of these details.
answered yesterday
Stephen Kitt
162k24362440
Thanks. In manpages.debian.org/stretch/sysvinit-core/…,initalso reacts to some signals. Does that mean we can communicate withinitby sending some signals instead of using FIFO, asking it to switch to the corresponding runlevel?
– Tim
23 hours ago
/run/initctlis FIFO not socket. Let me know if I am wrong.
– Tim
22 hours ago
You can use certain signals to communicate withsysvinit’sinit, but none of them are relevant here. You can’t use them to request an arbitrary runlevel change.
– Stephen Kitt
20 hours ago
add a comment |
up vote
3
down vote
accepted
With both sysvinit and systemd, shutting the operating system down starts by notifying the init process (the process with pid 1) that the system should shut down (or reboot, or power off).
sysvinit does this by using the /run/initctl FIFO to communicate with init, asking it to switch to the corresponding runlevel. See the init manpage for a brief overview.
systemd supports a variety of ways to do this. Various signals can be used to request a shutdown, reboot, etc., in various flavours; it’s also possible to request this over d-bus (the busctl manpage explains how to explore that).
Once pid 1 has been asked to shut down, it follows its configuration and specification and goes through all the appropriate steps for it. This typically includes notifying all users that a shutdown is in progress, shutting down all the running services (in a managed way with systemd; using shutdown scripts in various forms with sysvinit), syncing the mounted file systems, possibly unmounting them, killing all remaining processes (with the usual TERM then KILL sequence), and finally calling the kernel’s reboot system call with the appropriate parameters.
This describes the general sequence. There are many more twists to all this, including access control (with Polkit), various available hooks, kexec, sudden power-off handling, CtrlAltDel handling... The systemd documentation covers many of these details.
answered yesterday
Stephen Kitt
162k24362440
Thanks. In manpages.debian.org/stretch/sysvinit-core/…,initalso reacts to some signals. Does that mean we can communicate withinitby sending some signals instead of using FIFO, asking it to switch to the corresponding runlevel?
– Tim
23 hours ago
/run/initctlis FIFO not socket. Let me know if I am wrong.
– Tim
22 hours ago
You can use certain signals to communicate withsysvinit’sinit, but none of them are relevant here. You can’t use them to request an arbitrary runlevel change.
– Stephen Kitt
20 hours ago
add a comment |
up vote
3
down vote
accepted
up vote
3
down vote
accepted
With both sysvinit and systemd, shutting the operating system down starts by notifying the init process (the process with pid 1) that the system should shut down (or reboot, or power off).
sysvinit does this by using the /run/initctl FIFO to communicate with init, asking it to switch to the corresponding runlevel. See the init manpage for a brief overview.
systemd supports a variety of ways to do this. Various signals can be used to request a shutdown, reboot, etc., in various flavours; it’s also possible to request this over d-bus (the busctl manpage explains how to explore that).
Once pid 1 has been asked to shut down, it follows its configuration and specification and goes through all the appropriate steps for it. This typically includes notifying all users that a shutdown is in progress, shutting down all the running services (in a managed way with systemd; using shutdown scripts in various forms with sysvinit), syncing the mounted file systems, possibly unmounting them, killing all remaining processes (with the usual TERM then KILL sequence), and finally calling the kernel’s reboot system call with the appropriate parameters.
This describes the general sequence. There are many more twists to all this, including access control (with Polkit), various available hooks, kexec, sudden power-off handling, CtrlAltDel handling... The systemd documentation covers many of these details.
answered yesterday
Stephen Kitt
162k24362440
With both sysvinit and systemd, shutting the operating system down starts by notifying the init process (the process with pid 1) that the system should shut down (or reboot, or power off).
sysvinit does this by using the /run/initctl FIFO to communicate with init, asking it to switch to the corresponding runlevel. See the init manpage for a brief overview.
systemd supports a variety of ways to do this. Various signals can be used to request a shutdown, reboot, etc., in various flavours; it’s also possible to request this over d-bus (the busctl manpage explains how to explore that).
Once pid 1 has been asked to shut down, it follows its configuration and specification and goes through all the appropriate steps for it. This typically includes notifying all users that a shutdown is in progress, shutting down all the running services (in a managed way with systemd; using shutdown scripts in various forms with sysvinit), syncing the mounted file systems, possibly unmounting them, killing all remaining processes (with the usual TERM then KILL sequence), and finally calling the kernel’s reboot system call with the appropriate parameters.
This describes the general sequence. There are many more twists to all this, including access control (with Polkit), various available hooks, kexec, sudden power-off handling, CtrlAltDel handling... The systemd documentation covers many of these details.
answered yesterday
Stephen Kitt
162k24362440
edited 20 hours ago
answered yesterday
Stephen Kitt
162k24362440
answered yesterday
Stephen Kitt
162k24362440
answered yesterday
Stephen Kitt
162k24362440
162k24362440
Thanks. In manpages.debian.org/stretch/sysvinit-core/…,initalso reacts to some signals. Does that mean we can communicate withinitby sending some signals instead of using FIFO, asking it to switch to the corresponding runlevel?
– Tim
23 hours ago
/run/initctlis FIFO not socket. Let me know if I am wrong.
– Tim
22 hours ago
You can use certain signals to communicate withsysvinit’sinit, but none of them are relevant here. You can’t use them to request an arbitrary runlevel change.
– Stephen Kitt
20 hours ago
add a comment |
Thanks. In manpages.debian.org/stretch/sysvinit-core/…,initalso reacts to some signals. Does that mean we can communicate withinitby sending some signals instead of using FIFO, asking it to switch to the corresponding runlevel?
– Tim
23 hours ago
/run/initctlis FIFO not socket. Let me know if I am wrong.
– Tim
22 hours ago
You can use certain signals to communicate withsysvinit’sinit, but none of them are relevant here. You can’t use them to request an arbitrary runlevel change.
– Stephen Kitt
20 hours ago
Thanks. In manpages.debian.org/stretch/sysvinit-core/…,
init also reacts to some signals. Does that mean we can communicate with init by sending some signals instead of using FIFO, asking it to switch to the corresponding runlevel?– Tim
23 hours ago
Thanks. In manpages.debian.org/stretch/sysvinit-core/…,
init also reacts to some signals. Does that mean we can communicate with init by sending some signals instead of using FIFO, asking it to switch to the corresponding runlevel?– Tim
23 hours ago
/run/initctl is FIFO not socket. Let me know if I am wrong.– Tim
22 hours ago
/run/initctl is FIFO not socket. Let me know if I am wrong.– Tim
22 hours ago
You can use certain signals to communicate with
sysvinit’s init, but none of them are relevant here. You can’t use them to request an arbitrary runlevel change.– Stephen Kitt
20 hours ago
You can use certain signals to communicate with
sysvinit’s init, but none of them are relevant here. You can’t use them to request an arbitrary runlevel change.– Stephen Kitt
20 hours ago
add a comment |
Maybe at a high level with only critical parts?
– Tim
yesterday
Don't be afraid. Since you mentioned it, I would refrain myself from doing so.
– Tim
yesterday