tree-wide: remove Emacs lines from all files This should be handled fine now by .dir-locals.el, so need to carry that stuff in every file.

nspawn: optionally run a stub init process as PID 1 This adds a new switch --as-pid2, which allows running commands as PID 2, while a stub init process is run as PID 1. This is useful in order to run arbitrary commands in a container, as PID1's semantics are different from all other processes regarding reaping of unknown children or signal handling.

nspawn: add new --chdir= switch Fixes: #2192

nspawn: add new --network-veth-extra= switch for defining additional veth links The new switch operates like --network-veth, but may be specified multiple times (to define multiple link pairs) and allows flexible definition of the interface names. This is an independent reimplementation of #1678, but defines different semantics, keeping the behaviour completely independent of --network-veth. It also comes will full hook-up for .nspawn files, and the matching documentation.

process-util: move a couple of process-related calls over

util-lib: split out allocation calls into alloc-util.[ch]

nspawn: rework how we determine private networking settings Make sure we acquire CAP_NET_ADMIN if we require virtual networking. Make sure we imply virtual ethernet correctly when bridge is request. Fixes: #1511 Fixes: #1554 Fixes: #1590

tree-wide: clean up log_syntax() usage - Rely everywhere that we use abs() on the error code passed in anyway, thus don't need to explicitly negate what we pass in - Never attach synthetic error number information to log messages. Only log about errors we *receive* with the error number we got there, don't log any synthetic error, that don#t even propagate, but just eat up. - Be more careful with attaching exactly the error we get, instead of errno or unrelated errors randomly. - Fix one occasion where the error number and line number got swapped. - Make sure we never tape over OOM issues, or inability to resolve specifiers

nspawn: remove nspawn.h, it's empty now

nspawn: add new .nspawn files for container settings .nspawn fiels are simple settings files that may accompany container images and directories and contain settings otherwise passed on the nspawn command line. This provides an efficient way to attach execution data directly to containers.