The s6-fdholder-transferdump program
s6-fdholder-transferdump connects to two separate
fd-holding daemons and
transfers the content of the first one to the second one.
s6-fdholder-transferdump [ -t timeoutfrom:timeoutto ] pathfrom pathto
- s6-fdholder-transferdump connects to a
s6-fdholderd server process listening on
pathfrom and gets the whole set of file descriptors from
this server, with their identifiers and (when relevant) expiration
- It then connects to a different instance of
s6-fdholderd, listening on pathto,
and stores the set of file descriptors to it. The set is
added to the second server, which keeps the descriptors
it was already holding.
- -t timeoutfrom:timeoutto :
if the operations cannot be
processed in timeoutfrom (for the connection to pathfrom)
or timeoutto (for the connection to pathto) milliseconds,
then fail with an error message.
Communications with the servers should be near-instant, so this option is
only here to protect users against programming errors (connecting to the
wrong socket, for instance).
- 0: success.
- 1: the source server denied the operation. The meaning of the error messages
is explained here.
- 2: the destination server denied the operation. The meaning of the error messages
is explained here.
- 100: wrong usage.
- 111: system call failed - that includes attempting to connect to a
nonexistent socket, or one where no s6-fdholderd
daemon is listening.
- Dumping the entire state of s6-fdholderd
requires special authorizations. Make sure the s6-fdholderd instances are
configured to accept
dump-getting and dump-setting requests from your client.
- A typical use case of
when the main fd-holding daemon needs to upgrade, or restart for some reason.
Transferring the file descriptors into another, temporary fd-holding daemon
instance allows it to restart without losing the descriptors.