Intermediate Functional Block
The Intermediate Functional Block (ifb) pseudo network interface acts as a QoS concentrator for multiple different sources of traffic. Packets from or to other interfaces have to be redirected to it using the mirred action in order to be handled, regularly routed traffic will be dropped. This way, a single stack of qdiscs, classes and filters can be shared between multiple interfaces.
Here's a simple example to feed incoming traffic from multiple interfaces through a Stochastic Fairness Queue (sfq):
(1) # modprobe ifb
(2) # ip link set ifb0 up
(3) # tc qdisc add dev ifb0 root sfq
This option is an indication for PID1 that the entry in crypttab is handled by
initrd only and therefore it shouldn't interfer during the usual start-up and
shutdown process.
It should be primarily used with the encrypted device containing the root FS as
we want to keep it (and thus its encrypted device) until the very end of the
shutdown process, i.e. when initrd takes over.
This option is the counterpart of "x-initrd.mount" used in fstab.
Note that the slice containing the cryptsetup services also needs to drop the
usual shutdown dependencies as it's required by the cryptsetup services.
Fixes: #14224
Stochastic Fairness Queueing is a classless queueing discipline.
SFQ does not shape traffic but only schedules the transmission of packets, based on 'flows'.
The goal is to ensure fairness so that each flow is able to send data in turn,
thus preventing any single flow from drowning out the rest.
The actual burst limit is modified by the remaining disk space. This
isn't mentioned anywhere in the available documentation and might be a
source of surprise for an end user expecting certain behaviors.
We don't, the signal remains blocked. We use signalfd() to be able to
read the signal events without unblocking the signal.
While we are at it, mention that pthread_sigmask() is fine too.
The docs didn't talk about this, so let's add an explicit mention that the
boot loader must cooperate. And also make the message from the generator
notice level. This should help people who are trying to mix grub and the
gpt auto logic.
Let's make sure we get back to 100% man page documentation coverage of
our sd-event APIs. We are bad enough at the others, let's get these ones
right at least.
We dropped documentation from sd_journal_open_container() long ago
(since the call is obsolete), hence drop the reference to machined. But
add one in for journald instead.
systemd.nspawn(5) contained a partial repeat of the stuff that is now in the
dedicated man page. Let's just refer to that.
While at it, do s/searched/searched for/ where appropriate and reword some
sentences for brevity.
In those two pages, we need to include individual entries with xi:include to
merge the list less-variables.xml with the other entries, which is obviously
error prone. All variables are supported in both tools so add them.
