* gnu/build/file-systems.scm (read-ext2-superblock*, partition-predicate): New
procedures.
(partition-label-predicate): Rewrite in terms of 'partition-predicate'.
(partition-uuid-predicate, find-partition-by-uuid, uuid->string): New
procedures.
(%network-byte-order): New macro.
(canonicalize-device-spec)[canonical-title]: Check whether SPEC is a string.
[resolve]: New procedure.
Add 'uuid' case and use it.
* gnu/build/file-systems.scm: Import (guix build syscalls) when 'mount' is not
defined.
* gnu/system.scm (operating-system-activation-script): Include (guix build
syscalls) module in derivation.
Rather than expecting a pointer, the version of 'mount' in
guile-static-stripped now takes a string for the 'options' argument, just like
the 'mount' procedure in (guix build syscalls).
* gnu/packages/patches/guile-linux-syscalls.patch (mount): Expect a string or
#f for 'options' argument.
* gnu/build/file-systems.scm (mount-file-system): Use new 'mount' interface.
* gnu/build/file-systems.scm (MS_REMOUNT): New constant.
(mount-file-system): Add 'flags' local variable. When FLAGS has
MS_BIND & MS_RDONLY, call 'mount' with MS_REMOUNT.
* gnu/services/base.scm (file-system-service) <start>: Likewise.
* gnu/build/file-systems.scm (mount-file-system): When OPTIONS is false,
write "rw" to /etc/mtab. This fixes a bug whereby 'remove-from-mtab'
in (guix syscalls) would otherwise raise a 'match-error' because of
the missing field. This affected file systems mounted from the
initrd, such as devtmpfs, which has options == #f.
