;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org> ;;; Copyright © 2016, 2017 David Craven <david@craven.ch> ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com> ;;; ;;; 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 (gnu system uuid) #:use-module (gnu system file-systems) #:use-module (guix build utils) #:use-module (guix build bournish) #:use-module ((guix build syscalls) #:hide (file-system-type)) #: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 partition-uuid-predicate partition-luks-uuid-predicate find-partition-by-label find-partition-by-uuid find-partition-by-luks-uuid canonicalize-device-spec read-partition-label read-partition-uuid read-luks-partition-uuid 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: (define (bind-mount source target) "Bind-mount SOURCE at TARGET." (mount source target "" MS_BIND)) (define (seek* fd/port offset whence) "Like 'seek' but return -1 instead of throwing to 'system-error' upon EINVAL. This makes it easier to catch cases like OFFSET being too large for FD/PORT." (catch 'system-error (lambda () (seek fd/port offset whence)) (lambda args (if (= EINVAL (system-error-errno args)) -1 (apply throw args))))) (define (read-superblock device offset size magic?) "Read a superblock of SIZE from OFFSET and DEVICE. Return the raw superblock on success, and #f if no valid superblock was found. MAGIC? takes a bytevector and returns #t when it's a valid superblock." (call-with-input-file device (lambda (port) (and (= offset (seek* port offset SEEK_SET)) (let ((block (make-bytevector size))) (match (get-bytevector-n! port block 0 (bytevector-length block)) ((? eof-object?) #f) ((? number? len) (and (= len (bytevector-length block)) (and (magic? block) block))))))))) (define null-terminated-latin1->string (cut latin1->string <> zero?)) ;;; ;;; Ext2 file systems. ;;; ;; <http://www.nongnu.org/ext2-doc/ext2.html#DEF-SUPERBLOCK>. ;; TODO: Use "packed structs" from Guile-OpenGL or similar. (define-syntax %ext2-endianness ;; Endianness of ext2 file systems. (identifier-syntax (endianness little))) (define (ext2-superblock? sblock) "Return #t when SBLOCK is an ext2 superblock." (let ((magic (bytevector-u16-ref sblock 56 %ext2-endianness))) (= magic #xef53))) (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." (read-superblock device 1024 264 ext2-superblock?)) (define (ext2-superblock-uuid sblock) "Return the UUID of ext2 superblock SBLOCK as a 16-byte bytevector." (sub-bytevector sblock 104 16)) (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." (null-terminated-latin1->string (sub-bytevector sblock 120 16))) (define (check-ext2-file-system device) "Return the health of an ext2 file system on DEVICE." (match (status:exit-val (system* "e2fsck" "-v" "-p" "-C" "0" device)) (0 'pass) (1 'errors-corrected) (2 'reboot-required) (_ 'fatal-error))) ;;; ;;; Btrfs file systems. ;;; ;; <https://btrfs.wiki.kernel.org/index.php/On-disk_Format#Superblock>. (define-syntax %btrfs-endianness ;; Endianness of btrfs file systems. (identifier-syntax (endianness little))) (define (btrfs-superblock? sblock) "Return #t when SBLOCK is a btrfs superblock." (bytevector=? (sub-bytevector sblock 64 8) (string->utf8 "_BHRfS_M"))) (define (read-btrfs-superblock device) "Return the raw contents of DEVICE's btrfs superblock as a bytevector, or #f if DEVICE does not contain a btrfs file system." (read-superblock device 65536 4096 btrfs-superblock?)) (define (btrfs-superblock-uuid sblock) "Return the UUID of a btrfs superblock SBLOCK as a 16-byte bytevector." (sub-bytevector sblock 32 16)) (define (btrfs-superblock-volume-name sblock) "Return the volume name of SBLOCK as a string of at most 256 characters, or #f if SBLOCK has no volume name." (null-terminated-latin1->string (sub-bytevector sblock 299 256))) (define (check-btrfs-file-system device) "Return the health of a btrfs file system on DEVICE." (match (status:exit-val (system* "btrfs" "device" "scan")) (0 'pass) (_ 'fatal-error))) ;;; ;;; FAT32 file systems. ;;; ;; <http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-107.pdf>. (define (fat32-superblock? sblock) "Return #t when SBLOCK is a fat32 superblock." (bytevector=? (sub-bytevector sblock 82 8) (string->utf8 "FAT32 "))) (define (read-fat32-superblock device) "Return the raw contents of DEVICE's fat32 superblock as a bytevector, or #f if DEVICE does not contain a fat32 file system." (read-superblock device 0 90 fat32-superblock?)) (define (fat32-superblock-uuid sblock) "Return the Volume ID of a fat superblock SBLOCK as a 4-byte bytevector." (sub-bytevector sblock 67 4)) (define (fat32-superblock-volume-name sblock) "Return the volume name of SBLOCK as a string of at most 11 characters, or #f if SBLOCK has no volume name. The volume name is a latin1 string. Trailing spaces are trimmed." (string-trim-right (latin1->string (sub-bytevector sblock 71 11) (lambda (c) #f)) #\space)) (define (check-fat-file-system device) "Return the health of a fat file system on DEVICE." (match (status:exit-val (system* "fsck.vfat" "-v" "-a" device)) (0 'pass) (1 'errors-corrected) (_ 'fatal-error))) ;;; ;;; FAT16 file systems. ;;; (define (fat16-superblock? sblock) "Return #t when SBLOCK is a fat16 boot record." (bytevector=? (sub-bytevector sblock 54 8) (string->utf8 "FAT16 "))) (define (read-fat16-superblock device) "Return the raw contents of DEVICE's fat16 superblock as a bytevector, or #f if DEVICE does not contain a fat16 file system." (read-superblock device 0 62 fat16-superblock?)) (define (fat16-superblock-uuid sblock) "Return the Volume ID of a fat superblock SBLOCK as a 4-byte bytevector." (sub-bytevector sblock 39 4)) (define (fat16-superblock-volume-name sblock) "Return the volume name of SBLOCK as a string of at most 11 characters, or #f if SBLOCK has no volume name. The volume name is a latin1 string. Trailing spaces are trimmed." (string-trim-right (latin1->string (sub-bytevector sblock 43 11) (lambda (c) #f)) #\space)) ;;; ;;; ISO9660 file systems. ;;; ;; <http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-119.pdf>. (define (iso9660-superblock? sblock) "Return #t when SBLOCK is an iso9660 volume descriptor." (bytevector=? (sub-bytevector sblock 1 6) ;; Note: "\x01" is the volume descriptor format version (string->utf8 "CD001\x01"))) (define (read-iso9660-primary-volume-descriptor device offset) "Find and read the first primary volume descriptor, starting at OFFSET. Return #f if not found." (let* ((sblock (read-superblock device offset 2048 iso9660-superblock?)) (type-code (if sblock (bytevector-u8-ref sblock 0) (error (format #f "Could not read ISO9660 primary volume descriptor from ~s" device))))) (match type-code (255 #f) ; Volume Descriptor Set Terminator. (1 sblock) ; Primary Volume Descriptor (_ (read-iso9660-primary-volume-descriptor device (+ offset 2048)))))) (define (read-iso9660-superblock device) "Return the raw contents of DEVICE's iso9660 primary volume descriptor as a bytevector, or #f if DEVICE does not contain an iso9660 file system." ;; Start reading at sector 16. ;; Since we are not sure that the device contains an ISO9660 file system, ;; we have to find that out first. (if (read-superblock device (* 2048 16) 2048 iso9660-superblock?) (read-iso9660-primary-volume-descriptor device (* 2048 16)) #f)) ; Device does not contain an iso9660 file system. (define (iso9660-superblock-uuid sblock) "Return the modification time of an iso9660 primary volume descriptor SBLOCK as a bytevector. If that's not set, returns the creation time." ;; Drops GMT offset for compatibility with Grub, blkid and /dev/disk/by-uuid. ;; Compare Grub: "2014-12-02-19-30-23-00". ;; Compare blkid result: "2014-12-02-19-30-23-00". ;; Compare /dev/disk/by-uuid entry: "2014-12-02-19-30-23-00". (let* ((creation-time (sub-bytevector sblock 813 17)) (modification-time (sub-bytevector sblock 830 17)) (unset-time (make-bytevector 17 0)) (time (if (bytevector=? unset-time modification-time) creation-time modification-time))) (sub-bytevector time 0 16))) ; strips GMT offset. (define (iso9660-superblock-volume-name sblock) "Return the volume name of SBLOCK as a string. The volume name is an ASCII string. Trailing spaces are trimmed." ;; Note: Valid characters are of the set "[0-9][A-Z]_" (ECMA-119 Appendix A) (string-trim-right (latin1->string (sub-bytevector sblock 40 32) (lambda (c) #f)) #\space)) ;;; ;;; LUKS encrypted devices. ;;; ;; The LUKS header format is described in "LUKS On-Disk Format Specification": ;; <https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification>. We follow ;; version 1.2.1 of this document. (define-syntax %luks-endianness ;; Endianness of LUKS headers. (identifier-syntax (endianness big))) (define (luks-superblock? sblock) "Return #t when SBLOCK is a luks superblock." (define %luks-magic ;; The 'LUKS_MAGIC' constant. (u8-list->bytevector (append (map char->integer (string->list "LUKS")) (list #xba #xbe)))) (let ((magic (sub-bytevector sblock 0 6)) (version (bytevector-u16-ref sblock 6 %luks-endianness))) (and (bytevector=? magic %luks-magic) (= version 1)))) (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." ;; Size in bytes of the LUKS header, including key slots. (read-superblock file 0 592 luks-superblock?)) (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 (partition? name major minor) ;; grub-mkrescue does some funny things for EFI support which ;; makes it a lot more difficult than one would expect to support ;; booting an ISO-9660 image from an USB flash drive. ;; For example there's a buggy (too small) hidden partition in it ;; which Linux mounts and then proceeds to fail while trying to ;; fall off the edge. ;; In any case, partition tables are supposed to be optional so ;; here we allow checking entire disks for file systems, too. (> 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) ((= EIO errno) ;unreadable hardware like audio CDs (format (current-error-port) "warning: failed to read from device '~a'~%" device) #f) (else (apply throw args)))))))) (define (partition-field-reader read field) "Return a procedure that takes a device and returns the value of a FIELD in the partition superblock or #f." (let ((read (ENOENT-safe read))) (lambda (device) (let ((sblock (read device))) (and sblock (field sblock)))))) (define (read-partition-field device partition-field-readers) "Returns the value of a FIELD in the partition superblock of DEVICE or #f. It takes a list of PARTITION-FIELD-READERS and returns the result of the first partition field reader that returned a value." (match (filter-map (cut apply <> (list device)) partition-field-readers) ((field . _) field) (_ #f))) (define %partition-label-readers (list (partition-field-reader read-iso9660-superblock iso9660-superblock-volume-name) (partition-field-reader read-ext2-superblock ext2-superblock-volume-name) (partition-field-reader read-btrfs-superblock btrfs-superblock-volume-name) (partition-field-reader read-fat32-superblock fat32-superblock-volume-name) (partition-field-reader read-fat16-superblock fat16-superblock-volume-name))) (define %partition-uuid-readers (list (partition-field-reader read-iso9660-superblock iso9660-superblock-uuid) (partition-field-reader read-ext2-superblock ext2-superblock-uuid) (partition-field-reader read-btrfs-superblock btrfs-superblock-uuid) (partition-field-reader read-fat32-superblock fat32-superblock-uuid) (partition-field-reader read-fat16-superblock fat16-superblock-uuid))) (define read-partition-label (cut read-partition-field <> %partition-label-readers)) (define read-partition-uuid (cut read-partition-field <> %partition-uuid-readers)) (define luks-partition-field-reader (partition-field-reader read-luks-header luks-header-uuid)) (define read-luks-partition-uuid (cut read-partition-field <> (list luks-partition-field-reader))) (define (partition-predicate reader =) "Return a predicate that returns true if the FIELD of partition header that was READ is = to the given value." (lambda (expected) (lambda (device) (let ((actual (reader device))) (and actual (= actual expected)))))) (define partition-label-predicate (partition-predicate read-partition-label string=?)) (define partition-uuid-predicate (partition-predicate read-partition-uuid uuid=?)) (define luks-partition-uuid-predicate (partition-predicate luks-partition-field-reader uuid=?)) (define (find-partition predicate) "Return the first partition found that matches PREDICATE, or #f if none were found." (lambda (expected) (find (predicate expected) (map (cut string-append "/dev/" <>) (disk-partitions))))) (define find-partition-by-label (find-partition partition-label-predicate)) (define find-partition-by-uuid (find-partition partition-uuid-predicate)) (define find-partition-by-luks-uuid (find-partition luks-partition-uuid-predicate)) (define (canonicalize-device-spec spec) "Return the device name corresponding to SPEC, which can be a <uuid>, a <file-system-label>, or a string (typically a /dev file name)." (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 (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)))))))) (match spec ((? string?) ;; Nothing to do, but wait until SPEC shows up. (resolve identity spec identity)) ((? file-system-label?) ;; Resolve the label. (resolve find-partition-by-label (file-system-label->string spec) identity)) ((? uuid?) (resolve find-partition-by-uuid (uuid-bytevector spec) uuid->string)))) (define (check-file-system device type) "Run a file system check of TYPE on DEVICE." (define check-procedure (cond ((string-prefix? "ext" type) check-ext2-file-system) ((string-prefix? "btrfs" type) check-btrfs-file-system) ((string-suffix? "fat" type) check-fat-file-system) (else #f))) (if check-procedure (match (check-procedure device) ('pass #t) ('errors-corrected (format (current-error-port) "File system check corrected errors on ~a; continuing~%" device)) ('reboot-required (format (current-error-port) "File system check corrected errors on ~a; rebooting~%" device) (sleep 3) (reboot)) ('fatal-error (format (current-error-port) "File system check on ~a failed~%" device) ;; Spawn a REPL only if someone would be able to interact with it. (when (isatty? (current-input-port)) (format (current-error-port) "Spawning Bourne-like REPL.~%") ;; 'current-output-port' is typically connected to /dev/klog (in ;; PID 1), but here we want to make sure we talk directly to the ;; user. (with-output-to-file "/dev/console" (lambda () (start-repl %bournish-language)))))) (format (current-error-port) "No file system check procedure for ~a; skipping~%" device))) (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 fs #:key (root "/root")) "Mount the file system described by FS, a <file-system> object, under ROOT. 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." (define (mount-nfs source mount-point type flags options) (let* ((idx (string-rindex source #\:)) (host-part (string-take source idx)) ;; Strip [] from around host if present (host (match (string-split host-part (string->char-set "[]")) (("" h "") h) ((h) h))) (aa (match (getaddrinfo host "nfs") ((x . _) x))) (sa (addrinfo:addr aa)) (inet-addr (inet-ntop (sockaddr:fam sa) (sockaddr:addr sa)))) ;; Mounting an NFS file system requires passing the address ;; of the server in the addr= option (mount source mount-point type flags (string-append "addr=" inet-addr (if options (string-append "," options) ""))))) (let ((type (file-system-type fs)) (options (file-system-options fs)) (source (canonicalize-device-spec (file-system-device fs))) (mount-point (string-append root "/" (file-system-mount-point fs))) (flags (mount-flags->bit-mask (file-system-flags fs)))) (when (file-system-check? fs) (check-file-system source type)) ;; Create the mount point. Most of the time this is a directory, but ;; in the case of a bind mount, a regular file or socket may be needed. (if (and (= MS_BIND (logand flags MS_BIND)) (not (file-is-directory? source))) (unless (file-exists? mount-point) (mkdir-p (dirname mount-point)) (call-with-output-file mount-point (const #t))) (mkdir-p mount-point)) (cond ((string-prefix? "nfs" type) (mount-nfs source mount-point type flags options)) (else (mount source mount-point type flags options))) ;; For read-only bind mounts, an extra remount is needed, as per ;; <http://lwn.net/Articles/281157/>, 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