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Diffstat (limited to 'gnu/build/file-systems.scm')
| -rw-r--r-- | gnu/build/file-systems.scm | 299 |
1 files changed, 299 insertions, 0 deletions
diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm new file mode 100644 index 0000000000..5c04771e19 --- /dev/null +++ b/gnu/build/file-systems.scm @@ -0,0 +1,299 @@ +;;; GNU Guix --- Functional package management for GNU +;;; Copyright © 2014 Ludovic Courtès <ludo@gnu.org> +;;; +;;; 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 <http://www.gnu.org/licenses/>. + +(define-module (gnu build file-systems) + #:use-module (guix build utils) + #:use-module (rnrs io ports) + #:use-module (rnrs bytevectors) + #:use-module (ice-9 match) + #:use-module (ice-9 rdelim) + #: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 + find-partition-by-label + canonicalize-device-spec + + MS_RDONLY + MS_NOSUID + MS_NODEV + MS_NOEXEC + MS_BIND + MS_MOVE + bind-mount + + mount-flags->bit-mask + check-file-system + mount-file-system)) + +;;; Commentary: +;;; +;;; This modules provides tools to deal with disk partitions, and to mount and +;;; check file systems. +;;; +;;; Code: + +;; Linux mount flags, from libc's <sys/mount.h>. +(define MS_RDONLY 1) +(define MS_NOSUID 2) +(define MS_NODEV 4) +(define MS_NOEXEC 8) +(define MS_BIND 4096) +(define MS_MOVE 8192) + +(define (bind-mount source target) + "Bind-mount SOURCE at TARGET." + (mount source target "" MS_BIND)) + +(define-syntax %ext2-endianness + ;; Endianness of ext2 file systems. + (identifier-syntax (endianness little))) + +;; Offset in bytes of interesting parts of an ext2 superblock. See +;; <http://www.nongnu.org/ext2-doc/ext2.html#DEF-SUPERBLOCK>. +;; 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 <http://bugs.gnu.org/17466>. + (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)))))) + +(define (disk-partitions) + "Return the list of device names corresponding to valid disk partitions." + (define (partition? major minor) + (let ((marker (format #f "/sys/dev/block/~a:~a/partition" major minor))) + (catch 'system-error + (lambda () + (not (zero? (call-with-input-file marker read)))) + (lambda args + (if (= ENOENT (system-error-errno args)) + #f + (apply throw args)))))) + + (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? major minor) + (loop (cons name parts)) + (loop parts)))))))))) + +(define (partition-label-predicate label) + "Return a procedure that, when applied to a partition name such as \"sda1\", +return #t if that partition's volume name is LABEL." + (lambda (part) + (let* ((device (string-append "/dev/" part)) + (sblock (catch 'system-error + (lambda () + (read-ext2-superblock 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. + (if (= ENOENT (system-error-errno args)) + (begin + (format (current-error-port) + "warning: device '~a' not found~%" + device) + #f) + (apply throw args)))))) + (and sblock + (let ((volume (ext2-superblock-volume-name sblock))) + (and volume + (string=? volume label))))))) + +(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* (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\"; + • '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-prefix? "/" spec) + 'device + 'label) + title)) + + (case canonical-title + ((device) + ;; Nothing to do. + spec) + ((label) + ;; Resolve the label. + (let loop ((count 0)) + (let ((device (find-partition-by-label 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 label" spec) + (begin + (format #t "waiting for partition '~a' to appear...~%" + spec) + (sleep 1) + (loop (+ 1 count)))))))) + ;; TODO: Add support for UUIDs. + (else + (error "unknown device title" title)))) + +(define (check-file-system device type) + "Run a file system check of TYPE on DEVICE." + (define fsck + (string-append "fsck." type)) + + (let ((status (system* fsck "-v" "-p" device))) + (match (status:exit-val status) + (0 + #t) + (1 + (format (current-error-port) "'~a' corrected errors on ~a; continuing~%" + fsck device)) + (2 + (format (current-error-port) "'~a' corrected errors on ~a; rebooting~%" + fsck device) + (sleep 3) + (reboot)) + (code + (format (current-error-port) "'~a' exited with code ~a on ~a; spawning REPL~%" + fsck code device) + (start-repl))))) + +(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* (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))) + (when check? + (check-file-system source type)) + (mkdir-p mount-point) + (mount source mount-point type (mount-flags->bit-mask flags) + (if options + (string->pointer options) + %null-pointer)) + + ;; Update /etc/mtab. + (mkdir-p (string-append root "/etc")) + (let ((port (open-file (string-append root "/etc/mtab") "a"))) + (format port "~a ~a ~a ~a 0 0~%" + source mount-point type (or options "")) + (close-port port)))))) + +;;; file-systems.scm ends here |