Systemd: Difference between revisions
(→Automatically starting VDR when the storage is plugged in: Separate section "Shutting down VDR") |
(Documentation of the shutdown script) |
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then |
then |
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sudo sh /etc/systemd/system/vdr-keep-alive.sh stop |
sudo sh /etc/systemd/system/vdr-keep-alive.sh stop |
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sudo systemctl poweroff |
exec sudo systemctl poweroff |
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fi |
fi |
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[ -n "${STORAGE:-}" ] && sudo systemd-mount "$STORAGE" |
[ -n "${STORAGE:-}" ] && sudo systemd-mount "$STORAGE" |
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</pre> |
</pre> |
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====Wake on timer==== |
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The script relies on the versatile command <code>rtcwake</code> for wake-on-timer control. |
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⚫ | |||
Adjust <code>HIBERN</code> to the time it takes to suspend to disk and resume from it. If this fails because no swap space has been configured, the script will fall back to suspend-to-RAM. |
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⚫ | If there is no real-time clock device for scheduling wake-up (say, on a Raspberry Pi), all [[rtcwake]] commands will fail. It would be the user's responsibility to shut down or wake up the system between recordings (or leave it running all the time). You might want to set <code>FALLBACK_SHUTDOWN_DELAY</code> at the start of the script to have an automatic shutdown (followed by manual wakeup) if the next scheduled recording is in distant enough future. |
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====Detachable storage==== |
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When the line starting with <code>#STORAGE=</code> is commented out, there will be no difference between the user pressing the Power button, and the system being shut down due to an inactivity timeout. |
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If you want to use detachable video storage, uncomment the line and adjust the directory name if needed. The rest of this section assumes that you have done so. |
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If any process is using the <code>STORAGE</code> mount point, the system will refuse to shut down for any reason (inactivity timeout, or the Power button being pressed). In VDR, an active recording or the playback of a recording (even a paused playback) counts as using the mount point. |
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If unmounting the <code>STORAGE</code> succeeds, and the Power button was pressed, the line starting with <code>if [ "$5" = 1</code> will power off the storage and shut down VDR. The rest of the system will remain powered on. The power LED indicator on a USB storage device will become an indicator of two things: |
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* whether it is safe to disconnect the cable; you can plug it in again to have VDR start up (on same or different drive) |
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* whether shutdown is possible, by pressing the Power button one more time |
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Some systems are unable to wake up after power-off; see [[rtcwake]] for details. On an affected system, you might want to remove the section starting with <code>if [ "$5" = 1</code> to let the power button press lead directly to suspend-to-disk or suspend-to-RAM, just like an inactivity timeout would. |
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===Notes=== |
===Notes=== |
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</pre> |
</pre> |
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If you use these commands, the storage device will remain mounted in the file system, and the status of the reboot and shutdown targets will not change. |
If you use these commands, the storage device will remain mounted in the file system, and the status of the reboot and shutdown targets will not change. |
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At the start of the <code>/var/lib/vdr/vdr-shutdown.sh</code> script, you can configure a few things. |
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⚫ | |||
# Adjust <code>BOOT_DELAY</code> to the time it takes to shutdown and restart your system, or to suspend to disk and resume from it. |
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# If you do not want to use detachable storage for the video storage, remove or comment out the line starting with <code>STORAGE=</code>. |
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If the power button is pressed while VDR is not running, the system will be shut down. On the first press (while VDR is running), the lines after <code>elif [ "$5" = 1 ]</code> will detach the storage and shut down VDR. Some systems do not support wake-on-timer after power-off; see [[rtcwake]] for details. On such systems, you might remove the section <code>elif [ "$5" = 1 ]</code> to let the power button press to lead to proceed to suspend-to-disk or suspend-to-RAM instead. |
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If the <code>STORAGE</code> variable has been set, and any process (VDR or anything else) is using that mount point, the system will refuse to shut down. The power LED indicator on a USB storage device will become an indicator on whether shutdown is possible. If VDR is the only user of <code>STORAGE</code>, an extremely slow "double click" of the power button on the remote control unit will power off the system. Note: An active recording or the playback of a recording (even a paused playback) will prevent shutdown. |
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⚫ |
Revision as of 19:39, 25 April 2023
Introduction
The main aim of systemd (a "system and service manager") is to unify service configuration and behavior across Linux distributions. It bootstraps the user space and manages user processes. It also provides replacements for various daemons and utilities, including device management, login management, network connection management, and event logging.
Since 2015, the majority of Linux distributions have adopted systemd, having replaced other init systems such as SysV init.
Preventing shutdown and reboot while VDR is running
By default, the power button on a remote control that is managed by a kernel LIRC driver will be mapped to systemd-logind
. Unless you have overridden the default HandlePowerKey=poweroff
in /etc/systemd/logind.conf
, the system would be shut down immediately when you hit a power button on any input device (remote control, keyboard, or power button on the computer case).
Often, VDR is the main application on the system. You would not want the system to be accidentally shut down or rebooted while someone is watching TV, or a recording is in progress. System shutdown would be initiated by a script that would be invoked by VDR itself; see the -s
parameter of ExecStart
below.
To disable or enable the normal handling of shutdown and reboot, you can use the following script, say, /etc/systemd/system/vdr-keep-alive.sh
. Executing it will require super user privileges.
#!/bin/sh TARGETS=" /lib/systemd/system/poweroff.target.d /lib/systemd/system/reboot.target.d /lib/systemd/system/halt.target.d " CONF=vdr-keep-alive.conf case "$1" in start) for t in $TARGETS do if [ ! -f "$t/$CONF" ] then if [ ! -d "$t/" ] then mkdir "$t" fi echo "[Unit]\nRefuseManualStart=yes" > "$t/$CONF" fi done ;; stop) for t in $TARGETS do rm -f "$t/$CONF" done ;; esac exec systemctl daemon-reload
You can execute this script as follows:
sudo /etc/systemd/system/vdr-keep-alive.sh start sudo /etc/systemd/system/vdr-keep-alive.sh stop
You might want to make the TARGETS
above to include suspend
, hibernate
, or others mentioned in man 7 systemd.special
.
Making Systemd start up VDR
Before systemd, you might have edited /etc/gettydefs
to prevent a virtual console from being associated with a normal login prompt, and then have init
invoke a shell script that would invoke VDR, often named runvdr
. With systemd, all you need is a single file, say, /etc/systemd/system/vdr.service
, with contents like the following:
[Unit] Description=Video Disk Recorder After=systemd-user-sessions.service plymouth-quit-wait.service After=rc-local.service After=getty@tty1.service Conflicts=getty@tty1.service Conflicts=shutdown.target ConditionPathExists=/video/video [Service] User=pi ExecStartPre=+/etc/systemd/system/vdr-keep-alive.sh start ExecStart=/usr/local/bin/vdr --no-kbd --lirc=/dev/lirc0 -Prpihddevice -v /video/video -s /var/lib/vdr/vdr-shutdown.sh TimeoutStartSec=infinity Type=idle Restart=on-failure RestartSec=1s TTYVTDisallocate=yes [Install] WantedBy=display-manager.service
Adjustments
User=
refers to the user account that will run the VDR service.ExecStart=
must refer to the full VDR invocation.ConditionPathExists=
is for the directory that contains the recordings, matching the-v
parameter inExecStart
. If the recordings cannot be mounted, the service would not start up.
The shutdown script (named /var/lib/vdr/vdr-shutdown.sh
in the above example) could do at least one of the following:
- Invoke
sudo /etc/systemd/system/vdr-keep-alive.sh stop
to allow normal reboot and shutdown. - Adjust rtcwake (or Nvram_wakeup) to have the system start up automatically on the next scheduled recording.
- Invoke
sudo systemctl stop vdr
orsudo systemctl halt
to shut down VDR or the entire system. This will also terminate the shell that runs the script!
Installation
sudo systemctl enable vdr sudo systemctl start vdr
or just (according to man systemctl
):
sudo systemctl enable --now vdr
Example: Auto-starting VDR with swappable video storage
On a small system like the Raspberry_Pi, the internal storage is just large enough for the basic installation and system configuration. For recordings, you might want to use a USB-powered HDD or SSD.
You might make a virtue out of necessity and implement swappable video directories. One USB SSD might not be large enough for your entire collection of recordings. So, why not implement swappable storage, with the following user interface?
- When you plug in the USB cable (or it is attached on system startup), VDR will start up automatically.
- When you press the power button, VDR will shut down and the USB storage will be powered off, so that it can be safely unplugged.
- When you plug in the USB cable again, VDR will start up again. This could be a different drive.
Preparations
Create a file system and label it VDR
. Create the subdirectory video
inside it.
Below, we assume that the storage devices that you want to initialize is /dev/sdd. Substitute the correct name for sdd
below, and ensure that you are accessing the right device!
sudo mkfs.ext4 /dev/sdd1 sudo tune2fs -L /dev/sdd1 sudo mount /dev/sdd1 /mnt mkdir /mnt/video sudo umount /mnt
On the VDR system, create a mount point for the storage devices that have been prepared as above.
sudo mkdir -m 000 /video
Automatically mounting storage when it is plugged in
You might think of a simple /etc/fstab
entry like this:
LABEL=VDR /video ext4 defaults,noatime,nofail 0 1
But, we want the file system to be mounted automatically when it is labeled VDR. To achieve that, we create a file /etc/systemd/system/video.mount
(the name must match the mount point /video
):
[Unit] BindsTo=dev-disk-by\x2dlabel-VDR.device After=dev-disk-by\x2dlabel-VDR.device Requires=systemd-fsck@dev-disk-by\x2dlabel-VDR.service After=systemd-fsck@dev-disk-by\x2dlabel-VDR.service [Mount] Where=/video What=/dev/disk/by-label/VDR Type=ext4 Options=defaults,noatime,nofail [Install] WantedBy=dev-disk-by\x2dlabel-VDR.device
The magic .device
unit refers to the path /dev/disk/by-label/VDR
, which will become available when a device containing a file system labeled VDR
is attached. We use that name also in the What=
directive.
Now we are ready to enable the unit:
sudo systemctl enable video.mount
To check the status, you may find the following commands useful:
systemctl status journalctl -u video.mount journalctl -xe
Automatically starting VDR when the storage is plugged in
We also want VDR to start automatically once the file system has been mounted. To do that, the following lines have to be added to /etc/systemd/system/vdr.service
:
[Install] WantedBy=dev-disk-by\x2dlabel-VDR.device
If you had the following lines at the end of the file, they can be removed:
[Install] WantedBy=display-manager.service
To notify systemd of the update:
sudo systemctl reenable vdr
Shutting down VDR
Last, we need a VDR shutdown script /var/lib/vdr/vdr-shutdown.sh
that will power off the storage so that it can be safely detached, or shut down the system and schedule a restart for the next timer:
#!/bin/sh #exec >> /var/tmp/vdr-shutdown.txt 2>&1; set -x; : "$@" set -eu HIBERN=120 # time in seconds to suspend to disk + resume from it #FALLBACK_SHUTDOWN_DELAY=86400 # seconds #STORAGE=/dev/disk/by-label/VDR [ -n "${STORAGE:-}" ] && sudo systemd-mount -u "$STORAGE" if [ "$5" = 1 -a -n "${STORAGE:-}" ] then sudo rtcwake -m no -s "$2" || : sudo sh /etc/systemd/system/vdr-keep-alive.sh stop exec sudo udisksctl power-off -b "$STORAGE" elif [ "$2" = 0 ] then sudo sh /etc/systemd/system/vdr-keep-alive.sh stop sudo rtcwake -m disable || : exec sudo systemctl poweroff elif [ "$2" -ge $HIBERN ] && sudo rtcwake -m disk -s $(($2 - $HIBERN / 2)) then : elif sudo rtcwake -m mem -s "$2" then : elif [ "$2" -ge "${FALLBACK_SHUTDOWN_DELAY:-}" ] then sudo sh /etc/systemd/system/vdr-keep-alive.sh stop exec sudo systemctl poweroff fi [ -n "${STORAGE:-}" ] && sudo systemd-mount "$STORAGE"
Wake on timer
The script relies on the versatile command rtcwake
for wake-on-timer control.
You may want to replace the #exec
line with exec
to enable debug output to the file /var/tmp/vdr-shutdown.txt
. This file should survive system shutdown and restart.
Adjust HIBERN
to the time it takes to suspend to disk and resume from it. If this fails because no swap space has been configured, the script will fall back to suspend-to-RAM.
If there is no real-time clock device for scheduling wake-up (say, on a Raspberry Pi), all rtcwake commands will fail. It would be the user's responsibility to shut down or wake up the system between recordings (or leave it running all the time). You might want to set FALLBACK_SHUTDOWN_DELAY
at the start of the script to have an automatic shutdown (followed by manual wakeup) if the next scheduled recording is in distant enough future.
Detachable storage
When the line starting with #STORAGE=
is commented out, there will be no difference between the user pressing the Power button, and the system being shut down due to an inactivity timeout.
If you want to use detachable video storage, uncomment the line and adjust the directory name if needed. The rest of this section assumes that you have done so.
If any process is using the STORAGE
mount point, the system will refuse to shut down for any reason (inactivity timeout, or the Power button being pressed). In VDR, an active recording or the playback of a recording (even a paused playback) counts as using the mount point.
If unmounting the STORAGE
succeeds, and the Power button was pressed, the line starting with if [ "$5" = 1
will power off the storage and shut down VDR. The rest of the system will remain powered on. The power LED indicator on a USB storage device will become an indicator of two things:
- whether it is safe to disconnect the cable; you can plug it in again to have VDR start up (on same or different drive)
- whether shutdown is possible, by pressing the Power button one more time
Some systems are unable to wake up after power-off; see rtcwake for details. On an affected system, you might want to remove the section starting with if [ "$5" = 1
to let the power button press lead directly to suspend-to-disk or suspend-to-RAM, just like an inactivity timeout would.
Notes
You can still execute the following commands to stop or start the VDR service, for example, for upgrading VDR or plugins:
sudo systemctl stop vdr sudo systemctl start vdr
If you use these commands, the storage device will remain mounted in the file system, and the status of the reboot and shutdown targets will not change.