I've been fumbling around trying to get a satisfactory backup of my
Mac laptop to an external FireWire drive. I like the design
principles of rsnapshot much better than the (large) number of other
backup tools (including some very expensive commercial options).
There are a number of issues though, some relating to it being a Mac
(I've been using a Mac since '84, so I still have and still care
about things like resource forks) and some relating to it being a
laptop (it's not on full-time and not reliably configured the same
way all the time, so cron jobs aren't entirely reliable).
After a lot of fumbling around, I've come up with a scheme that seems
to back up *all* of the information I care about and which does so as
automatically and painlessly as possible when I plug in my backup
drive.
I wrote this up for my own purposes, just so I'd remember how to get
things working again when some future OS upgrade or hardware purchase
inevitably breaks things, but in the hopes that it might prove useful
to others, I offer it here.
Any comments or corrections are more than welcome.
=========================================================
What I did to back up a Mac to an external FireWire drive
=========================================================
:Author: Jonathan Guyer
:Contact: guyer < at > nist.gov
:Date: 19 April 2007
:Copyright: This document has been placed in the public domain
- Get, build and install ``rsync`` version 3 from `CVS
<http://rsync.samba.org/download.html>`_. The ``rsync`` shipped by
Apple
is buggy and the fixes proposed by http://www.onthenet.com.au/~q/
rsync/
and by http://lartmaker.nl/rsync/ don't work.
.. note::
If you don't care about Mac meta data (resource forks and such)
then
you don't need this, but are you *sure* you don't care about
Mac meta
data? You *are* using a Mac, right?
- Edit your ``rsnapshot.conf`` file
- set, e.g.::
snapshot_root /Volumes/Backup/snapshot/
and be sure to create the appropriate directory.
.. note::
If you wish to `Set the backup to run automatically when a
FireWire drive is mounted`_, you don't need to declare
``snapshot_root`` in the ``rsnapshot.conf`` file, but you do
still need to create the appropriate directories.
.. note::
The NFS protection schemes suggested in the ``rsnapshot``
documentation aren't too applicable to a Mac, but you can
protect
the backup directory from all but ``sudo``. This idea was
suggested by `Giuliano Gavazzi
<http://sourceforge.net/mailarchive/message.php?
msg_id=ED74A128-77F1-4856-B4CB-7291F5FD4C9D%40humph.com>`_
- Create a ``backup`` group using NetInfo Manager (not in
``/etc/groups``) containing all user accounts. (Is
there a more automatic
group that will accomplish this?)
- Use Access Control Lists (ACLs) to secure the backup
directory
- Enable ACLs::
$ sudo fsaclctl -p /Volumes/Backup -e
- Set desired ACLs::
$ sudo chmod +a "backup deny add_file,
delete, \
add_subdirectory, delete_child, writeattr,
writeextattr \
directory_inherit" /Volumes/Backup/snapshot
- set::
no_create_root 1
to prevent ``rsnapshot`` from making a mess in your ``/Volumes/``
directory when the drive is not mounted.
- set the path to the ``rsync`` you installed above::
cmd_rsync /usr/local/bin/rsync
- set the backup intervals appropriately
- pass the following arguments to ``rsync``::
rsync_short_args -a
rsync_long_args --delete --numeric-ids --relative --delete-
excluded --xattrs
The important one here for the Mac is ``--xattrs``. If you don't
care about Macish resource forks (are you sure you don't?),
then you
can omit this and you don't need ``rsync`` 3.
- you may want to set::
one_fs 1
- exclude transitory, dangerous, and boring things::
exclude /dev/
exclude /automount/
exclude /cores/
exclude /.vol/
exclude /Volumes/
exclude .Trashes/
exclude .Trash/
exclude .TemporaryItems/
exclude .Spotlight-V100/
exclude Library/Caches/
exclude Library/Safari/Icons/
exclude /private/tmp/
exclude /private/var/vm/
exclude /private/var/tmp/
exclude /private/var/spool/
exclude /private/var/launchd/
exclude /private/var/run/
- back up everything else::
backup / path.to.machine/
Backing up to ``path.to.machine`` is arbitrary, but makes it
easy to sort
things out later if you back up more than one thing and
``rsnapshot``
requires you to back up somewhere.
.. note:: Can you back up to ``.``?
.. attention::
If your home directory is protected by FileVault, then you'll
want to
add::
exclude /Users/.username/
to the excludes list and::
backup /Users/username/ path.to.machine/
to the backup list, otherwise the encrypted FileVault archive
will be
recopied, in its entirety, and the visible ``$HOME``
directory will be empty
in the backup.
.. caution::
If you do this, the backup ``$HOME`` directory will not be
encrypted.
Appropriate physical security measures must be taken with
the backup
drive.
Set the backup to run automatically when a FireWire drive is mounted
--------------------------------------------------------------------
- Apple's `exhortation to use the disk arbitration framework
<http://developer.apple.com/documentation/MacOSX/Conceptual/
BPSystemStartup/Articles/LaunchOnDemandDaemons.html#//apple_ref/doc/
uid/TP40001762-DontLinkElementID_14>`_
is somewhat less than helpful, and R. Matthew Emerson has a
peculiar
definition of "well-commented", but `his code
<http://www.thoughtstuff.com/rme/weblog/?p=3>`_ is a useful
starting
point::
// rsnapshotd
//
// Mac OS X daemon for detecting the mount of a backup
drive and launching
// rsnapshot
//
// Jonathan Guyer <guyer < at > nist.gov>
//
// This code is in the public domain
#include <stdio.h>
#include <syslog.h>
#include <CoreFoundation/CoreFoundation.h>
#include <DiskArbitration/DiskArbitration.h>
typedef struct {
CFUUIDRef uuid;
const char * snapshot_root_conf;
const char * snapshot_root_dir;
const char * cmd;
const char ** argv;
pid_t pid;
} tRsnapshotContext;
// Lifted from Steve Christensen on carbon-dev
char* CopyCStringFromCFString(CFStringRef cfString,
CFStringEncoding encoding)
{
CFIndex bufferSize = CFStringGetMaximumSizeForEncoding
(CFStringGetLength(cfString), encoding) + 1;
char* buffer = malloc(bufferSize);
if (buffer != NULL)
{
if (!CFStringGetCString(cfString, buffer,
bufferSize, encoding))
{
free(buffer);
buffer = NULL;
}
}
return buffer;
}
void hello_disk(DADiskRef disk, void *contextP)
{
CFDictionaryRef diskref = DADiskCopyDescription
(disk);
CFUUIDRef uuid = CFDictionaryGetValue
(diskref, kDADiskDescriptionVolumeUUIDKey);
tRsnapshotContext * context = (tRsnapshotContext *)
contextP;
diskref = DADiskCopyDescription(disk);
if (uuid != NULL && uuid == context->uuid) {
CFURLRef pathURL = CFDictionaryGetValue
(diskref, kDADiskDescriptionVolumePathKey);
CFStringRef uuidStr = CFUUIDCreateString
(kCFAllocatorDefault, uuid);
char * uuidCStr = CopyCStringFromCFString
(uuidStr, kCFStringEncodingUTF8);
if (pathURL != NULL) {
CFStringRef pathStr = CFURLCopyFileSystemPath
(pathURL, kCFURLPOSIXPathStyle);
char * path = CopyCStringFromCFString
(pathStr, kCFStringEncodingUTF8);
FILE * f = fopen(context-
snapshot_root_conf, "w");
syslog(LOG_NOTICE, "performing rsnapshot
backup to disk %s, UUID: %s", path, uuidCStr);
CFRelease(pathStr);
fprintf(f, "# This file automatically
generated by rsnapshotd\n");
fprintf(f, "snapshot_root\t%s/%s\n", path,
context->snapshot_root_dir);
fclose(f);
free(path);
} else {
syslog(LOG_NOTICE, "performing rsnapshot
backup to nameless disk, UUID: %s", uuidCStr);
}
free(uuidCStr);
CFRelease(uuidStr);
switch (context->pid = vfork()) {
case 0: { // child process
int err = execv(context->cmd, context-
argv);
syslog(LOG_ERR, "rsnapshot backup failed
to launch: %d", err);
exit(1); // in case exec fails
}
case -1:
syslog(LOG_ERR, "vfork failed");
break;
default: {
}
}
}
CFRelease(diskref);
}
// // This handler is pointless. The disk won't unmount as
long as the process is running,
// // so the the process must be killed first, which means
there's nothign to kill here.
// // I welcome suggestions of how to do something useful
with this
// void goodbye_disk(DADiskRef disk, void *contextP)
// {
// CFDictionaryRef diskref = DADiskCopyDescription
(disk);
// CFUUIDRef uuid = CFDictionaryGetValue
(diskref, kDADiskDescriptionVolumeUUIDKey);
// tRsnapshotContext * context = (tRsnapshotContext *)
contextP;
//
// diskref = DADiskCopyDescription(disk);
//
// if (uuid != NULL && uuid == context->uuid &&
context->pid != 0) {
// kill(context->pid, 3);
// printf("\n\ndisk unmounted\n");
// }
// }
int main (int argc, const char * argv[])
{
DASessionRef session;
CFStringRef uuidStr;
tRsnapshotContext context;
if (argc < 5) {
syslog(LOG_ERR, "Usage: rsnapshotd UUID
SNAPSHOT_ROOT.CONFIG SHAPSHOT_ROOT_DIR CMD [OPTION ...]");
exit(1);
}
uuidStr = CFStringCreateWithCString
(kCFAllocatorDefault, argv[1], kCFStringEncodingUTF8);
if (!uuidStr) {
syslog(LOG_ERR, "Unable to create UUID string");
exit(1);
}
context.uuid = CFUUIDCreateFromString
(kCFAllocatorDefault, uuidStr);
if (!context.uuid) {
syslog(LOG_ERR, "Unable to parse UUID string");
exit(1);
}
context.snapshot_root_conf = argv[2];
context.snapshot_root_dir = argv[3];
context.cmd = argv[4];
context.argv = &argv[4];
context.pid = -1;
session = DASessionCreate(kCFAllocatorDefault);
DARegisterDiskAppearedCallback(session, NULL,
hello_disk, &context);
// DARegisterDiskDisappearedCallback(session, NULL,
goodbye_disk, &context);
DASessionScheduleWithRunLoop(session,
CFRunLoopGetCurrent(),
kCFRunLoopDefaultMode);
CFRunLoopRun();
CFRelease(session);
exit(0);
}
If you save this as, e.g., ``rsnapshotd.c``, you can build it
with::
gcc -framework DiskArbitration -framework CoreFoundation
rsnapshotd.c -o rsnapshotd
``rsnapshotd`` takes four required arguments, followed by any
options to pass to the command:
``UUID``
The Universally Unique Identifier for the disk you
wish to
back up to. You can obtain the ``UUID`` by executing
``diskutil
info <device>`` (run ``diskutil list`` to find the
device ID).
``/PATH/TO/snapshot_root.conf``
The (writable) location of a file to put the path of the
backup disk. This is necessary.
.. attention::
You must be sure to include the line::
include_conf /PATH/TO/snapshot_root.conf
after (or in place of) the ``snapshot_root``
parameter in
your ``rsnapshot.conf`` file.
``snapshot_root_directory``
The relative path to the backup on the backup drive
associated with ``UUID``, e.g., ``snapshot/``.
``CMD``
The fully qualified path to ``rsnapshot``.
.. note::
There's nothing magical about ``rsnapshot``. This
daemon will
launch any command with any options you supply when
the
appropriate disk is mounted.
``ARGS``
Arguments to send to ``rsnapshot``, e.g., ``-c``,
``/PATH/TO/rsnapshot.conf`` and ``daily``.
- Rather than setting up a cron job, add a file
``net.sourceforge.rsnapshotd.plst`` to
``/Library/LaunchDaemons/``::
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC -//Apple Computer//DTD PLIST 1.0//EN
http://www.apple.com/DTDs/PropertyList-1.0.dtd >
<plist version="1.0">
<dict>
<key>Label</key>
<string>net.sourceforge.rsnapshotd</string>
<key>ProgramArguments</key>
<array>
<string>/PATH/TO/rsnapshotd</string>
<string>UUID</string>
<string>/PATH/TO/snapshot_root.conf</string>
<string>snapshot/</string>
<string>/PATH/TO/rsnapshot</string>
<string>-c</string>
<string>/PATH/TO/rsnapshot.conf</string>
<string>daily</string>
</array>
<key>OnDemand</key>
<false/>
<key>RunAtLoad</key>
<true/>
<key>LowPriorityIO</key>
<true/>
<key>Nice</key>
<integer>20</integer>
</dict>
</plist>
This will cause the daemon to sit quietly, waiting for the
disk to
mount (it will trigger if the disk is already mounted when the
daemon
is loaded). The ``LowPriorityIO`` and ``Nice`` keys should
prevent
the rsnapshot process from being too much of a resource hog
when it
launches (``LowPriorityIO`` is probably more important than
``Nice``).
- Install the daemon by executing::
$ sudo launchctl load /Library/LaunchDaemons/
net.sourceforge.rsnapshotd.plst
--
Jonathan E. Guyer, PhD
Metallurgy Division
National Institute of Standards and Technology
<http://www.metallurgy.nist.gov/>
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