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;;; nspawn-tramp.el -- TRAMP integration for systemd-nspawn containers -*- lexical-binding: t; -*-
;; Copyright © 2021 Brian Cully <bjc@kublai.com>
;; Author: Brian Cully <bjc@kublai.com>
;; URL: https://github.com/bjc/nspawn-tramp
;; Keywords: tramp, nspawn, machinectl, systemd, systemd-nspawn
;; Maintainer: Brian Cully <bjc@kublai.com>
;; Version: 0.1
;; Package-Requires: ((emacs "23"))
;;; License:
;; This program is free software; you can redistribute it and/or
;; modify it under the terms of the GNU General Public License as
;; published by the Free Software Foundation, either version 3 of the
;; License, or (at your option) any later version.
;; This program is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;; General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; ‘nspawn-tramp’ allows TRAMP to work with containers provided by
;; systemd-nspawn.
;;
;; ## Usage
;;
;; Open a file on a running systemd-nspawn container:
;;
;; C-x C-f /nspawn:user@container:/path/to/file
;;
;; Where:
;; ‘user’ is the user on the container to connect as (optional)
;; ‘container’ is the container to connect to
;;
;; ## Privileges
;;
;; systemd-nspawn and its container utilities often require super user
;; access to run, and this package does not do privilege escalation in
;; order to accomplish that.
;;
;; One way of working around this using TRAMP’s built-in multi-hop
;; facilities with doas or sudo to raise your privileges.
;;
;; Another possibility is using polkit(8) to allow specific users
;; access to the requisite services (machinectl).
;;
;;; Code:
(require 'tramp)
(defgroup nspawn-tramp nil
"TRAMP integration for systemd-nspawn containers."
:prefix "nspawn-tramp-"
:group 'applications
:link '(url-link :tag "Github" "https://github.com/bjc/nspawn-tramp")
:link '(emacs-commentary-link :tag "Commentary" "nspawn-tramp"))
(defcustom nspawn-tramp-machinectl-path "machinectl"
"Path to machinectl executable."
:type 'string
:group 'nspawn-tramp)
(defconst nspawn-tramp-method "nspawn"
"TRAMP method name to use to connect to systemd-nspawn containers.")
(defun nspawn-tramp--completion-function (&rest _args)
"List systemd-nspawn containers available for connection.
This function is used by ‘tramp-set-completion-function’, please
see its function help for a description of the format."
(let* ((raw-list (shell-command-to-string
(concat nspawn-tramp-machinectl-path
" list -q")))
(lines (cdr (split-string raw-list "\n")))
(first-words (mapcar (lambda (line) (car (split-string line)))
lines))
(machines (seq-take-while (lambda (name) name) first-words)))
(mapcar (lambda (m) (list nil m)) machines)))
(defun nspawn-tramp--add-method ()
"Add TRAMP method handler for nspawn conainers."
(push `(,nspawn-tramp-method
(tramp-login-program ,nspawn-tramp-machinectl-path)
(tramp-login-args (("shell")
("-q")
("--uid" "%u")
("%h")))
(tramp-remote-shell "/bin/sh")
(tramp-remote-shell-login ("-l"))
(tramp-remote-shell-args ("-i" "-c")))
tramp-methods))
(defun nspawn-tramp--remove-method ()
"Remove TRAMP method handler for nspawn conainers."
(setf (alist-get nspawn-tramp-method tramp-methods nil t 'string=) nil))
(defun nspawn-tramp-unload-function ()
"Remove TRAMP method handler and completion functions."
(tramp-set-completion-function nspawn-tramp-method nil)
(nspawn-tramp--remove-method)
nil)
;;;###autoload
(defun nspawn-tramp-setup ()
"Initialize systemd-nspawn support for TRAMP."
(nspawn-tramp--add-method)
(tramp-set-completion-function nspawn-tramp-method
'((nspawn-tramp--completion-function ""))))
;;;###autoload
(eval-after-load 'tramp
(nspawn-tramp-setup))
(provide 'nspawn-tramp)
;;; nspawn-tramp.el ends here
|
