mirror of
https://git.in.rschanz.org/ryan77627/guix.git
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71f0676a29
* gnu/system/privilege.scm (<privileged-program>): Add a field representing the program's POSIX capabilities. (privileged-program-capabilities): New public procedure. * doc/guix.texi (Privileged Programs): Document it. * gnu/build/activation.scm (activate-privileged-programs): Take a LIBCAP package argument providing setcap(8) to apply said capabilities. * gnu/services.scm (privileged-program->activation-gexp): Pass said package argument where supported. Include privileged-program-capabilities in the compatibility hack.
443 lines
18 KiB
Scheme
443 lines
18 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
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;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
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;;; Copyright © 2015, 2018 Mark H Weaver <mhw@netris.org>
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;;; Copyright © 2018 Arun Isaac <arunisaac@systemreboot.net>
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;;; Copyright © 2018, 2019 Ricardo Wurmus <rekado@elephly.net>
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;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
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;;; Copyright © 2020 Christine Lemmer-Webber <cwebber@dustycloud.org>
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;;; Copyright © 2021 Brice Waegeneire <brice@waegenei.re>
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;;; Copyright © 2022 Tobias Geerinckx-Rice <me@tobias.gr>
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;;; Copyright © 2024 Nicolas Graves <ngraves@ngraves.fr>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (gnu build activation)
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#:use-module (gnu system accounts)
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#:use-module (gnu system privilege)
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#:use-module (gnu build accounts)
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#:use-module (gnu build linux-boot)
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#:use-module (guix build utils)
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#:use-module ((guix build syscalls) #:select (with-file-lock))
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#:use-module (ice-9 ftw)
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#:use-module (ice-9 match)
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#:use-module (ice-9 vlist)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-11)
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#:use-module (srfi srfi-26)
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#:export (activate-users+groups
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activate-user-home
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activate-etc
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activate-privileged-programs
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activate-special-files
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activate-modprobe
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activate-firmware
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activate-ptrace-attach
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activate-current-system
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mkdir-p/perms))
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;;; Commentary:
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;;;
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;;; This module provides "activation" helpers. Activation is the process that
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;;; consists in setting up system-wide files and directories so that an
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;;; 'operating-system' configuration becomes active.
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;;;
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;;; Code:
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(define %skeleton-directory
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;; Directory containing skeleton files for new accounts.
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;; Note: keep the trailing '/' so that 'scandir' enters it.
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"/etc/skel/")
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(define (dot-or-dot-dot? file)
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(member file '("." "..")))
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;; Based upon mkdir-p from (guix build utils)
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(define (verify-not-symbolic dir)
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"Verify DIR or its ancestors aren't symbolic links."
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(define absolute?
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(string-prefix? "/" dir))
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(define not-slash
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(char-set-complement (char-set #\/)))
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(define (verify-component file)
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(unless (eq? 'directory (stat:type (lstat file)))
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(error "file name component is not a directory" dir)))
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(let loop ((components (string-tokenize dir not-slash))
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(root (if absolute?
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""
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".")))
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(match components
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((head tail ...)
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(let ((file (string-append root "/" head)))
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(catch 'system-error
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(lambda ()
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(verify-component file)
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(loop tail file))
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(lambda args
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(if (= ENOENT (system-error-errno args))
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#t
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(apply throw args))))))
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(() #t))))
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;; TODO: the TOCTTOU race can be addressed once guile has bindings
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;; for fstatat, openat and friends.
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(define (mkdir-p/perms directory owner bits)
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"Create the directory DIRECTORY and all its ancestors.
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Verify no component of DIRECTORY is a symbolic link.
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Warning: this is currently suspect to a TOCTTOU race!"
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(verify-not-symbolic directory)
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(mkdir-p directory)
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(chown directory (passwd:uid owner) (passwd:gid owner))
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(chmod directory bits))
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(define* (copy-account-skeletons home
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#:key
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(directory %skeleton-directory)
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uid gid)
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"Copy the account skeletons from DIRECTORY to HOME. When UID is an integer,
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make it the owner of all the files created except the home directory; likewise
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for GID."
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(define (set-owner file)
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(when (or uid gid)
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(chown file (or uid -1) (or gid -1))))
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(let ((files (scandir directory (negate dot-or-dot-dot?)
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string<?)))
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(mkdir-p home)
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(for-each (lambda (file)
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(let ((target (string-append home "/" file)))
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(copy-recursively (string-append directory "/" file)
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target
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#:log (%make-void-port "w"))
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(for-each set-owner
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(find-files target (const #t)
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#:directories? #t))
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(make-file-writable target)))
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files)))
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(define* (make-skeletons-writable home
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#:optional (directory %skeleton-directory))
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"Make sure that the files that have been copied from DIRECTORY to HOME are
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owner-writable in HOME."
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(let ((files (scandir directory (negate dot-or-dot-dot?)
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string<?)))
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(for-each (lambda (file)
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(let ((target (string-append home "/" file)))
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(when (file-exists? target)
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(make-file-writable target))))
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files)))
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(define (duplicates lst)
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"Return elements from LST present more than once in LST."
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(let loop ((lst lst)
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(seen vlist-null)
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(result '()))
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(match lst
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(()
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(reverse result))
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((head . tail)
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(loop tail
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(vhash-cons head #t seen)
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(if (vhash-assoc head seen)
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(cons head result)
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result))))))
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(define (activate-users+groups users groups)
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"Make sure USERS (a list of user account records) and GROUPS (a list of user
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group records) are all available."
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(define (make-home-directory user)
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(let ((home (user-account-home-directory user))
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(pwd (getpwnam (user-account-name user))))
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(mkdir-p home)
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;; Always set ownership and permissions for home directories of system
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;; accounts. If a service needs looser permissions on its home
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;; directories, it can always chmod it in an activation snippet.
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(chown home (passwd:uid pwd) (passwd:gid pwd))
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(chmod home #o700)))
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(define system-accounts
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(filter (lambda (user)
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(and (user-account-system? user)
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(user-account-create-home-directory? user)))
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users))
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;; Allow home directories to be created under /var/lib.
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(mkdir-p "/var/lib")
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;; Take same lock as libc's 'lckpwdf' (but without a timeout) while we read
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;; and write the databases. This ensures there's no race condition with
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;; other tools that might be accessing it at the same time.
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(with-file-lock %password-lock-file
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(let-values (((groups passwd shadow)
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(user+group-databases users groups)))
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(write-group groups)
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(write-passwd passwd)
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(write-shadow shadow)))
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;; Home directories of non-system accounts are created by
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;; 'activate-user-home'.
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(for-each make-home-directory system-accounts)
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;; Turn shared home directories, such as /var/empty, into root-owned,
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;; read-only places.
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(for-each (lambda (directory)
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(chown directory 0 0)
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(chmod directory #o555))
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(duplicates (map user-account-home-directory system-accounts))))
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(define (activate-user-home users)
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"Create and populate the home directory of USERS, a list of tuples, unless
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they already exist."
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(define ensure-user-home
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(lambda (user)
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(let ((name (user-account-name user))
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(home (user-account-home-directory user))
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(create-home? (user-account-create-home-directory? user))
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(system? (user-account-system? user)))
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;; The home directories of system accounts are created during
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;; activation, not here.
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(unless (or (not home) (not create-home?) system?
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(directory-exists? home))
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(let* ((pw (getpwnam name))
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(uid (passwd:uid pw))
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(gid (passwd:gid pw)))
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(mkdir-p home)
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(chmod home #o700)
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(copy-account-skeletons home
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#:uid uid #:gid gid)
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;; It is important 'chown' be called after
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;; 'copy-account-skeletons'. Otherwise, a malicious user with
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;; good timing could create a symlink in HOME that would be
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;; dereferenced by 'copy-account-skeletons'.
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(chown home uid gid))))))
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(for-each ensure-user-home users))
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(define (activate-etc etc)
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"Install ETC, a directory in the store, as the source of static files for
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/etc."
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;; /etc is a mixture of static and dynamic settings. Here is where we
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;; initialize it from the static part.
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(define (rm-f file)
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(false-if-exception (delete-file file)))
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(format #t "populating /etc from ~a...~%" etc)
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(mkdir-p "/etc")
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;; Create the /etc/ssl -> /run/current-system/profile/etc/ssl symlink. This
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;; symlink, to a target outside of the store, probably doesn't belong in the
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;; static 'etc' store directory. However, if it were to be put there,
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;; beware that if /run/current-system/profile/etc/ssl doesn't exist at the
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;; time of activation (e.g. when installing a fresh system), the call to
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;; 'file-is-directory?' below will fail because it uses 'stat', not 'lstat'.
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(rm-f "/etc/ssl")
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(symlink "/run/current-system/profile/etc/ssl" "/etc/ssl")
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(rm-f "/etc/static")
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(symlink etc "/etc/static")
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(for-each (lambda (file)
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(let ((target (string-append "/etc/" file))
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(source (string-append "/etc/static/" file)))
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(rm-f target)
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;; Things such as /etc/sudoers must be regular files, not
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;; symlinks; furthermore, they could be modified behind our
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;; back---e.g., with 'visudo'. Thus, make a copy instead of
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;; symlinking them.
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(if (file-is-directory? source)
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(symlink source target)
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(copy-file source target))
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;; XXX: Dirty hack to meet sudo's expectations.
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(when (string=? (basename target) "sudoers")
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(chmod target #o440))))
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(scandir etc (negate dot-or-dot-dot?)
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;; The default is 'string-locale<?', but we don't have
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;; it when run from the initrd's statically-linked
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;; Guile.
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string<?)))
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(define %setuid-directory
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;; Place where setuid programs used to be stored. It exists for backwards
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;; compatibility & will be removed. Use %PRIVILEGED-PROGRAM-DIRECTORY instead.
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"/run/setuid-programs")
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(define %privileged-program-directory
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;; Place where privileged copies of programs are stored.
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"/run/privileged/bin")
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(define (activate-privileged-programs programs libcap)
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"Turn PROGRAMS, a list of file privileged-programs records, into privileged
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copies stored under %PRIVILEGED-PROGRAM-DIRECTORY, using LIBCAP's setcap(8)
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binary if needed."
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(define (ensure-empty-directory directory)
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(if (file-exists? directory)
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(for-each (compose delete-file
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(cut string-append directory "/" <>))
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(scandir directory
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(lambda (file)
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(not (member file '("." ".."))))
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string<?))
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(mkdir-p directory)) )
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(define (make-privileged-program program setuid? setgid? uid gid capabilities)
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(let ((target (string-append %privileged-program-directory
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"/" (basename program)))
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(mode (+ #o0555 ; base permissions
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(if setuid? #o4000 0) ; setuid bit
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(if setgid? #o2000 0)))) ; setgid bit
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(copy-file program target)
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(chown target uid gid)
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(chmod target mode)
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(when (and capabilities libcap)
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(system* (string-append libcap "/sbin/setcap")
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"-q" capabilities target))))
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(define (make-deprecated-wrapper program)
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;; This will eventually become a script that warns on usage, then vanish.
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(symlink (string-append %privileged-program-directory
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"/" (basename program))
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(string-append %setuid-directory
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"/" (basename program))))
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(format #t "setting up privileged programs in '~a'...~%"
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%privileged-program-directory)
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(ensure-empty-directory %privileged-program-directory)
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(ensure-empty-directory %setuid-directory)
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(for-each (lambda (program)
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(catch 'system-error
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(lambda ()
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(let* ((program-name (privileged-program-program program))
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(setuid? (privileged-program-setuid? program))
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(setgid? (privileged-program-setgid? program))
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(user (privileged-program-user program))
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(group (privileged-program-group program))
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(capabilities (privileged-program-capabilities program))
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(uid (match user
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((? string?) (passwd:uid (getpwnam user)))
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((? integer?) user)))
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(gid (match group
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((? string?) (group:gid (getgrnam group)))
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((? integer?) group))))
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(make-privileged-program program-name
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setuid? setgid? uid gid
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capabilities)
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(make-deprecated-wrapper program-name)))
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(lambda args
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;; If we fail to create a privileged program, better keep going
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;; so that we don't leave %PRIVILEGED-PROGRAM-DIRECTORY empty
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;; or half-populated. This can happen if PROGRAMS contains
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;; incorrect file names: <https://bugs.gnu.org/38800>.
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(format (current-error-port)
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"warning: failed to privilege ~s: ~a~%"
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(privileged-program-program program)
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(strerror (system-error-errno args))))))
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programs))
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(define (activate-special-files special-files)
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"Install the files listed in SPECIAL-FILES. Each element of SPECIAL-FILES
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is a pair where the first element is the name of the special file and the
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second element is the name it should appear at, such as:
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((\"/bin/sh\" \"/gnu/store/…-bash/bin/sh\")
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(\"/usr/bin/env\" \"/gnu/store/…-coreutils/bin/env\"))
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"
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(define install-special-file
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(match-lambda
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((target file)
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(let ((pivot (string-append target ".new")))
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(mkdir-p (dirname target))
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(symlink file pivot)
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(rename-file pivot target)))))
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(for-each install-special-file special-files))
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(define (activate-modprobe modprobe)
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"Tell the kernel to use MODPROBE to load modules."
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;; If the kernel was built without loadable module support, this file is
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;; unavailable, so check for its existence first.
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(when (file-exists? "/proc/sys/kernel/modprobe")
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(call-with-output-file "/proc/sys/kernel/modprobe"
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(lambda (port)
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(display modprobe port)))))
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(define (activate-firmware directory)
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"Tell the kernel to look for device firmware under DIRECTORY. This
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mechanism bypasses udev: it allows Linux to handle firmware loading directly
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by itself, without having to resort to a \"user helper\"."
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;; If the kernel was built without firmware loading support, this file
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;; does not exist. Do nothing in that case.
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(let ((firmware-path "/sys/module/firmware_class/parameters/path"))
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(when (file-exists? firmware-path)
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(call-with-output-file firmware-path
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(lambda (port)
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(display directory port))))))
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(define (activate-ptrace-attach)
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"Allow users to PTRACE_ATTACH their own processes.
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This works around a regression introduced in the default \"security\" policy
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found in Linux 3.4 onward that prevents users from attaching to their own
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processes--see Yama.txt in the Linux source tree for the rationale. This
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sounds like an unacceptable restriction for little or no security
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improvement."
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(let ((file "/proc/sys/kernel/yama/ptrace_scope"))
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(when (file-exists? file)
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(call-with-output-file file
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(lambda (port)
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(display 0 port))))))
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(define %current-system
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;; The system that is current (a symlink.) This is not necessarily the same
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;; as the system we booted (aka. /run/booted-system) because we can re-build
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;; a new system configuration and activate it, without rebooting.
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"/run/current-system")
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(define (boot-time-system)
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"Return the 'gnu.system' argument passed on the kernel command line."
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(find-long-option "gnu.system" (if (string-contains %host-type "linux-gnu")
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(linux-command-line)
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(command-line))))
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(define* (activate-current-system
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#:optional (system (or (getenv "GUIX_NEW_SYSTEM")
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(boot-time-system))))
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"Atomically make SYSTEM the current system."
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;; The 'GUIX_NEW_SYSTEM' environment variable is used as a way for 'guix
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;; system reconfigure' to pass the file name of the new system.
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(format #t "making '~a' the current system...~%" system)
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(mkdir-p "/run")
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;; Atomically make SYSTEM current.
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(let ((new (string-append %current-system ".new")))
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(symlink system new)
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(rename-file new %current-system)))
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;;; activation.scm ends here
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