;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2014, 2015, 2016 Ludovic Courtès ;;; ;;; This file is part of GNU Guix. ;;; ;;; GNU Guix 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. ;;; ;;; GNU Guix 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 GNU Guix. If not, see . (define-module (gnu build file-systems) #:use-module (guix build utils) #:use-module (guix build bournish) #:use-module (guix build syscalls) #:use-module (rnrs io ports) #:use-module (rnrs bytevectors) #:use-module (ice-9 match) #:use-module (ice-9 rdelim) #:use-module (ice-9 format) #:use-module (ice-9 regex) #:use-module (system foreign) #:autoload (system repl repl) (start-repl) #:use-module (srfi srfi-1) #:use-module (srfi srfi-26) #:export (disk-partitions partition-label-predicate partition-uuid-predicate partition-luks-uuid-predicate find-partition-by-label find-partition-by-uuid find-partition-by-luks-uuid canonicalize-device-spec uuid->string string->uuid bind-mount mount-flags->bit-mask check-file-system mount-file-system) #:re-export (mount umount MS_BIND MS_MOVE MS_RDONLY)) ;;; Commentary: ;;; ;;; This modules provides tools to deal with disk partitions, and to mount and ;;; check file systems. ;;; ;;; Code: ;; 'mount' is already defined in the statically linked Guile used for initial ;; RAM disks, in which case the bindings in (guix build syscalls) do not work ;; (the FFI bindings do not work there). Override them in that case. (when (module-defined? the-scm-module 'mount) (set! mount (@ (guile) mount)) (set! umount (@ (guile) umount))) (define (bind-mount source target) "Bind-mount SOURCE at TARGET." (mount source target "" MS_BIND)) ;;; ;;; Ext2 file systems. ;;; (define-syntax %ext2-endianness ;; Endianness of ext2 file systems. (identifier-syntax (endianness little))) ;; Offset in bytes of interesting parts of an ext2 superblock. See ;; . ;; TODO: Use "packed structs" from Guile-OpenGL or similar. (define-syntax %ext2-sblock-magic (identifier-syntax 56)) (define-syntax %ext2-sblock-creator-os (identifier-syntax 72)) (define-syntax %ext2-sblock-uuid (identifier-syntax 104)) (define-syntax %ext2-sblock-volume-name (identifier-syntax 120)) (define (read-ext2-superblock device) "Return the raw contents of DEVICE's ext2 superblock as a bytevector, or #f if DEVICE does not contain an ext2 file system." (define %ext2-magic ;; The magic bytes that identify an ext2 file system. #xef53) (define superblock-size ;; Size of the interesting part of an ext2 superblock. 264) (define block ;; The superblock contents. (make-bytevector superblock-size)) (call-with-input-file device (lambda (port) (seek port 1024 SEEK_SET) ;; Note: work around . (and (eqv? superblock-size (get-bytevector-n! port block 0 superblock-size)) (let ((magic (bytevector-u16-ref block %ext2-sblock-magic %ext2-endianness))) (and (= magic %ext2-magic) block)))))) (define (ext2-superblock-uuid sblock) "Return the UUID of ext2 superblock SBLOCK as a 16-byte bytevector." (let ((uuid (make-bytevector 16))) (bytevector-copy! sblock %ext2-sblock-uuid uuid 0 16) uuid)) (define (ext2-superblock-volume-name sblock) "Return the volume name of SBLOCK as a string of at most 16 characters, or #f if SBLOCK has no volume name." (let ((bv (make-bytevector 16))) (bytevector-copy! sblock %ext2-sblock-volume-name bv 0 16) ;; This is a Latin-1, nul-terminated string. (let ((bytes (take-while (negate zero?) (bytevector->u8-list bv)))) (if (null? bytes) #f (list->string (map integer->char bytes)))))) ;;; ;;; LUKS encrypted devices. ;;; ;; The LUKS header format is described in "LUKS On-Disk Format Specification": ;; . We follow ;; version 1.2.1 of this document. (define-syntax %luks-endianness ;; Endianness of LUKS headers. (identifier-syntax (endianness big))) (define-syntax %luks-header-size ;; Size in bytes of the LUKS header, including key slots. (identifier-syntax 592)) (define %luks-magic ;; The 'LUKS_MAGIC' constant. (u8-list->bytevector (append (map char->integer (string->list "LUKS")) (list #xba #xbe)))) (define (sub-bytevector bv start size) "Return a copy of the SIZE bytes of BV starting from offset START." (let ((result (make-bytevector size))) (bytevector-copy! bv start result 0 size) result)) (define (read-luks-header file) "Read a LUKS header from FILE. Return the raw header on success, and #f if not valid header was found." (call-with-input-file file (lambda (port) (let ((header (make-bytevector %luks-header-size))) (match (get-bytevector-n! port header 0 (bytevector-length header)) ((? eof-object?) #f) ((? number? len) (and (= len (bytevector-length header)) (let ((magic (sub-bytevector header 0 6)) ;XXX: inefficient (version (bytevector-u16-ref header 6 %luks-endianness))) (and (bytevector=? magic %luks-magic) (= version 1) header))))))))) (define (luks-header-uuid header) "Return the LUKS UUID from HEADER, as a 16-byte bytevector." ;; 40 bytes are reserved for the UUID, but in practice, it contains the 36 ;; bytes of its ASCII representation. (let ((uuid (sub-bytevector header 168 36))) (string->uuid (utf8->string uuid)))) ;;; ;;; Partition lookup. ;;; (define (disk-partitions) "Return the list of device names corresponding to valid disk partitions." (define (last-character str) (string-ref str (- (string-length str) 1))) (define (partition? name major minor) ;; Select device names that end in a digit, like libblkid's 'probe_all' ;; function does. Checking for "/sys/dev/block/MAJOR:MINOR/partition" ;; doesn't work for partitions coming from mapped devices. (and (char-set-contains? char-set:digit (last-character name)) (> major 2))) ;ignore RAM disks and floppy disks (call-with-input-file "/proc/partitions" (lambda (port) ;; Skip the two header lines. (read-line port) (read-line port) ;; Read each subsequent line, and extract the last space-separated ;; field. (let loop ((parts '())) (let ((line (read-line port))) (if (eof-object? line) (reverse parts) (match (string-tokenize line) (((= string->number major) (= string->number minor) blocks name) (if (partition? name major minor) (loop (cons name parts)) (loop parts)))))))))) (define (ENOENT-safe proc) "Wrap the one-argument PROC such that ENOENT errors are caught and lead to a warning and #f as the result." (lambda (device) (catch 'system-error (lambda () (proc device)) (lambda args ;; When running on the hand-made /dev, ;; 'disk-partitions' could return partitions for which ;; we have no /dev node. Handle that gracefully. (let ((errno (system-error-errno args))) (cond ((= ENOENT errno) (format (current-error-port) "warning: device '~a' not found~%" device) #f) ((= ENOMEDIUM errno) ;for removable media #f) (else (apply throw args)))))))) (define (partition-predicate read field =) "Return a predicate that returns true if the FIELD of partition header that was READ is = to the given value." (let ((read (ENOENT-safe read))) (lambda (expected) "Return a procedure that, when applied to a partition name such as \"sda1\", returns #t if that partition's volume name is LABEL." (lambda (part) (let* ((device (string-append "/dev/" part)) (sblock (read device))) (and sblock (let ((actual (field sblock))) (and actual (= actual expected))))))))) (define partition-label-predicate (partition-predicate read-ext2-superblock ext2-superblock-volume-name string=?)) (define partition-uuid-predicate (partition-predicate read-ext2-superblock ext2-superblock-uuid bytevector=?)) (define partition-luks-uuid-predicate (partition-predicate read-luks-header luks-header-uuid bytevector=?)) (define (find-partition-by-label label) "Return the first partition found whose volume name is LABEL, or #f if none were found." (and=> (find (partition-label-predicate label) (disk-partitions)) (cut string-append "/dev/" <>))) (define (find-partition-by-uuid uuid) "Return the first partition whose unique identifier is UUID (a bytevector), or #f if none was found." (and=> (find (partition-uuid-predicate uuid) (disk-partitions)) (cut string-append "/dev/" <>))) (define (find-partition-by-luks-uuid uuid) "Return the first LUKS partition whose unique identifier is UUID (a bytevector), or #f if none was found." (and=> (find (partition-luks-uuid-predicate uuid) (disk-partitions)) (cut string-append "/dev/" <>))) ;;; ;;; UUIDs. ;;; (define-syntax %network-byte-order (identifier-syntax (endianness big))) (define (uuid->string uuid) "Convert UUID, a 16-byte bytevector, to its string representation, something like \"6b700d61-5550-48a1-874c-a3d86998990e\"." ;; See . (let ((time-low (bytevector-uint-ref uuid 0 %network-byte-order 4)) (time-mid (bytevector-uint-ref uuid 4 %network-byte-order 2)) (time-hi (bytevector-uint-ref uuid 6 %network-byte-order 2)) (clock-seq (bytevector-uint-ref uuid 8 %network-byte-order 2)) (node (bytevector-uint-ref uuid 10 %network-byte-order 6))) (format #f "~8,'0x-~4,'0x-~4,'0x-~4,'0x-~12,'0x" time-low time-mid time-hi clock-seq node))) (define %uuid-rx ;; The regexp of a UUID. (make-regexp "^([[:xdigit:]]{8})-([[:xdigit:]]{4})-([[:xdigit:]]{4})-([[:xdigit:]]{4})-([[:xdigit:]]{12})$")) (define (string->uuid str) "Parse STR as a DCE UUID (see ) and return its contents as a 16-byte bytevector. Return #f if STR is not a valid UUID representation." (and=> (regexp-exec %uuid-rx str) (lambda (match) (letrec-syntax ((hex->number (syntax-rules () ((_ index) (string->number (match:substring match index) 16)))) (put! (syntax-rules () ((_ bv index (number len) rest ...) (begin (bytevector-uint-set! bv index number (endianness big) len) (put! bv (+ index len) rest ...))) ((_ bv index) bv)))) (let ((time-low (hex->number 1)) (time-mid (hex->number 2)) (time-hi (hex->number 3)) (clock-seq (hex->number 4)) (node (hex->number 5)) (uuid (make-bytevector 16))) (put! uuid 0 (time-low 4) (time-mid 2) (time-hi 2) (clock-seq 2) (node 6))))))) (define* (canonicalize-device-spec spec #:optional (title 'any)) "Return the device name corresponding to SPEC. TITLE is a symbol, one of the following: • 'device', in which case SPEC is known to designate a device node--e.g., \"/dev/sda1\"; • 'label', in which case SPEC is known to designate a partition label--e.g., \"my-root-part\"; • 'uuid', in which case SPEC must be a UUID (a 16-byte bytevector) designating a partition; • 'any', in which case SPEC can be anything. " (define max-trials ;; Number of times we retry partition label resolution, 1 second per ;; trial. Note: somebody reported a delay of 16 seconds (!) before their ;; USB key would be detected by the kernel, so we must wait for at least ;; this long. 20) (define canonical-title ;; The realm of canonicalization. (if (eq? title 'any) (if (string? spec) ;; The "--root=SPEC" kernel command-line option always provides a ;; string, but the string can represent a device, a UUID, or a ;; label. So check for all three. (cond ((string-prefix? "/" spec) 'device) ((string->uuid spec) 'uuid) (else 'label)) 'uuid) title)) (define (resolve find-partition spec fmt) (let loop ((count 0)) (let ((device (find-partition spec))) (or device ;; Some devices take a bit of time to appear, most notably USB ;; storage devices. Thus, wait for the device to appear. (if (> count max-trials) (error "failed to resolve partition" (fmt spec)) (begin (format #t "waiting for partition '~a' to appear...~%" (fmt spec)) (sleep 1) (loop (+ 1 count)))))))) (case canonical-title ((device) ;; Nothing to do. spec) ((label) ;; Resolve the label. (resolve find-partition-by-label spec identity)) ((uuid) (resolve find-partition-by-uuid (if (string? spec) (string->uuid spec) spec) uuid->string)) (else (error "unknown device title" title)))) (define (check-file-system file-system) "Run a file system check on FILE-SYSTEM." (let* ((fsck (file-system-check-procedure file-system)) (status (fsck device))) (match (status:exit-val status) (0 #t) (1 (format (current-error-port) "'~a' corrected errors; continuing~%" fsck)) (2 (format (current-error-port) "'~a' corrected errors; rebooting~%" fsck) (sleep 3) (reboot)) (code (format (current-error-port) "'~a' exited with code ~a; \ spawning Bourne-like REPL~%" fsck code) (start-repl %bournish-language))))) (define (mount-flags->bit-mask flags) "Return the number suitable for the 'flags' argument of 'mount' that corresponds to the symbols listed in FLAGS." (let loop ((flags flags)) (match flags (('read-only rest ...) (logior MS_RDONLY (loop rest))) (('bind-mount rest ...) (logior MS_BIND (loop rest))) (('no-suid rest ...) (logior MS_NOSUID (loop rest))) (('no-dev rest ...) (logior MS_NODEV (loop rest))) (('no-exec rest ...) (logior MS_NOEXEC (loop rest))) (() 0)))) (define (regular-file? file-name) "Return #t if FILE-NAME is a regular file." (eq? (stat:type (stat file-name)) 'regular)) (define* (mount-file-system spec #:key (root "/root")) "Mount the file system described by SPEC under ROOT. SPEC must have the form: (DEVICE TITLE MOUNT-POINT TYPE (FLAGS ...) OPTIONS CHECK?) DEVICE, MOUNT-POINT, and TYPE must be strings; OPTIONS can be a string or #f; FLAGS must be a list of symbols. CHECK? is a Boolean indicating whether to run a file system check." (match spec ((source title mount-point type (flags ...) options check?) (let ((source (canonicalize-device-spec source title)) (mount-point (string-append root "/" mount-point)) (flags (mount-flags->bit-mask flags))) (when check? (check-file-system (spec->file-system spec))) ;; Create the mount point. Most of the time this is a directory, but ;; in the case of a bind mount, a regular file may be needed. (if (and (= MS_BIND (logand flags MS_BIND)) (regular-file? source)) (unless (file-exists? mount-point) (mkdir-p (dirname mount-point)) (call-with-output-file mount-point (const #t))) (mkdir-p mount-point)) (mount source mount-point type flags options) ;; For read-only bind mounts, an extra remount is needed, as per ;; , which still applies to Linux 4.0. (when (and (= MS_BIND (logand flags MS_BIND)) (= MS_RDONLY (logand flags MS_RDONLY))) (let ((flags (logior MS_BIND MS_REMOUNT MS_RDONLY))) (mount source mount-point type flags #f))))))) ;;; file-systems.scm ends here