Add memory_id program to set properties about the physical memory
devices in the system. This is useful on machines with removable memory
modules to show how the machine can be upgraded, and on all devices to
detect the actual RAM size, without relying on the OS accessible amount.
Closes: #16651
This is useful for development where overwriting files out side
the configured prefix will affect the host as well as stateless
systems such as NixOS that don't let packages install to /etc but handle
configuration on their own.
Alternative to https://github.com/systemd/systemd/pull/17501
tested with:
$ mkdir inst build && cd build
$ meson \
-Dcreate-log-dirs=false \
-Dsysvrcnd-path=$(realpath ../inst)/etc/rc.d \
-Dsysvinit-path=$(realpath ../inst)/etc/init.d \
-Drootprefix=$(realpath ../inst) \
-Dinstall-sysconfdir=false \
--prefix=$(realpath ../inst) ..
$ ninja install
... when called with a valid environment variable name. This means that
any time we call it with a fixed string, it is guaranteed to return 0.
(Also when the variable is not present in the environment block.)
Previously it was very likely, when multiple contenders for the symlink
appear in parallel, that algorithm would select wrong symlink (i.e. one
with lower-priority).
Now the algorithm is much more defensive and when we detect change in
set of contenders for the symlink we reevaluate the selection. Same
happens when new symlink replaces already existing symlink that points
to different device node.
* Existing valid rule files written with KEY="value" are not affected
* Now, KEY=e"value\n" becomes valid. Where `\n` is a newline character
* Escape sequences supported by src/basic/escape.h:cunescape() is
supported
Previously, .device units generated by SYSTEMD_ALIAS= udev properties
are not supported to specify devices for e.g. 'udevadm info'.
Before:
```
$ udevadm info sys-subsystem-net-devices-enp0s31f6.device
Unknown device "sys-subsystem-net-devices-enp0s31f6.device": No such device
```
After:
```
$ ./udevadm info sys-subsystem-net-devices-enp0s31f6.device
P: /devices/pci0000:00/0000:00:1f.6/net/enp0s31f6
L: 0
E: DEVPATH=/devices/pci0000:00/0000:00:1f.6/net/enp0s31f6
E: INTERFACE=enp0s31f6
E: IFINDEX=2
E: SUBSYSTEM=net
E: USEC_INITIALIZED=25317523
E: ID_NET_NAMING_SCHEME=v245
(snip)
```
Negative value means there is no match between a PCI device and any of
the slots. In the following commit we will extend this and value of 0
will indicate that there is a match between some slot and PCI device,
but that device is a PCI bridge.
This fixes a race where a block device that pops up and immediately is
locked (such as a loopback device in preparation) might result in
udev never run any rules for it, and thus never turn on inotify watching
for it (as inotify watching is controlled via an option set via udev
rules), thus not noticing when the device is unlocked/closed again
(which is noticed via IN_CLOSE_WRITE inotify events).
This changes two things:
1. Whenever we encounter a locked block device we'll now inotify watch
it, so that it is guaranteed we'll notice when the BSD lock fd is
closed again, and will reprobe.
2. We'll now turn off inotify watching again once we realise the
udev rules don't actually want that. Previously, once watching a
device was enabled via a udev rule, it would be watched forever until
the device disappeared, even if the option was dropped by the rules
for later events.
Together this will make sure that we'll watch the device via inotify
in both of the following cases:
a) The block device has been BSD locked when udev wanted to look at it
b) The udev rules run for the last seen event for the device say so
In all other cases inotify is off for block devices.
This new behaviour both fixes the race, but also makes the most sense,
as the rules (when they are run) actually really control the watch state
now. And if someone BSD locks a block device then it should be OK to
inotify watch it briefly until the lock is released again as the user
this way more or less opts into the locking protocol.
This effectively reverts commit 67acde4869.
After commits 569ad251ad and
67acde4869, -EACCES errors are ignored,
and thus 'udevadm trigger' succeeds even when it is invoked by non-root
users. Moreover, on -EACCES error, log messages are shown in debug
level, so usually we see no message, and users are easily confused
why uevents for devices are not triggered.
Bastien Nocera