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I've discovered a strange problem... if I have disk image files (DMGs) which reside on a read-only NFS share, I cannot open these in Mac OS X 10.7.5. The same files open fine when accessed over AFP. However, trying to open them using hdiutil attach when they're on the NFS share results in "attach failed - Read-only file system":

bash-3.2# /usr/bin/hdiutil attach /Volumes/nfs_share/Some.dmg
hdiutil: attach failed - Read-only file system

Even if the AFP share is read-only, I can attach those same images. But for some reason, a read-only NFS share doesn't work.

Ultimately what I want to do is attach the images with a shadow file, to mount the read-only images as read-write. But this also fails the same way:

bash-3.2# /usr/bin/hdiutil attach /Volumes/nfs_share/Some.dmg -mountpoint /Somewhere -shadow /path/to/Some-Shadow
hdiutil: attach failed - Read-only file system

Again, this works perfectly if the image is served via AFP. It also works fine if the NFS share is read-write, but for security reasons I cannot do that.

How can I mount DMG files which reside on a read-only NFS share?


Additional information:

The relevant line from /etc/exports on the FreeNAS (FreeBSD 8.2-RELEASE-p7) server:

/mnt/raid/netboot -alldirs -ro -mapall=netboot:netboot -network 10.100.0.0/16

The output of /usr/bin/hdiutil attach -verbose /Volumes/netboot/Lion.nbi/Library.dmg -notremovable -shadow /private/var/netboot/Library-Shadow -owners on -noverify -noautofsck -nobrowse:

Initializing…
DIBackingStoreInstantiatorProbe: interface  0, score      100, CBSDBackingStore
DIBackingStoreInstantiatorProbe: interface  1, score    -1000, CBundleBackingStore
DIBackingStoreInstantiatorProbe: interface  2, score    -1000, CRAMBackingStore
DIBackingStoreInstantiatorProbe: interface  3, score      100, CCarbonBackingStore
DIBackingStoreInstantiatorProbe: interface  4, score    -1000, CDevBackingStore
DIBackingStoreInstantiatorProbe: interface  5, score    -1000, CCURLBackingStore
DIBackingStoreInstantiatorProbe: interface  6, score    -1000, CVectoredBackingStore
CBSDBackingStore::newProbe stat() failed.  No such file or directory.
DIBackingStoreInstantiatorProbe: interface  0, score        1, CBSDBackingStore
DIBackingStoreInstantiatorProbe: interface  1, score    -1000, CBundleBackingStore
DIBackingStoreInstantiatorProbe: interface  2, score    -1000, CRAMBackingStore
DIBackingStoreInstantiatorProbe: interface  3, score    -1000, CCarbonBackingStore
DIBackingStoreInstantiatorProbe: interface  4, score    -1000, CDevBackingStore
DIBackingStoreInstantiatorProbe: interface  5, score    -1000, CCURLBackingStore
DIBackingStoreInstantiatorProbe: interface  6, score    -1000, CVectoredBackingStore
DIBackingStoreInstantiatorProbe: interface  0, score      100, CBSDBackingStore
DIBackingStoreInstantiatorProbe: interface  1, score    -1000, CBundleBackingStore
DIBackingStoreInstantiatorProbe: interface  2, score    -1000, CRAMBackingStore
DIBackingStoreInstantiatorProbe: interface  3, score      100, CCarbonBackingStore
DIBackingStoreInstantiatorProbe: interface  4, score    -1000, CDevBackingStore
DIBackingStoreInstantiatorProbe: interface  5, score    -1000, CCURLBackingStore
DIBackingStoreInstantiatorProbe: interface  6, score    -1000, CVectoredBackingStore
Attaching…
Error 30 (Read-only file system).
Finishing…
DIHLDiskImageAttach() returned 30
hdiutil: attach failed - Read-only file system

Output of rpcinfo -p on the NFS Server:

   program vers proto   port  service
    100000    4   tcp    111  rpcbind
    100000    3   tcp    111  rpcbind
    100000    2   tcp    111  rpcbind
    100000    4   udp    111  rpcbind
    100000    3   udp    111  rpcbind
    100000    2   udp    111  rpcbind
    100000    4 local    111  rpcbind
    100000    3 local    111  rpcbind
    100000    2 local    111  rpcbind
    100005    1   udp    967  mountd
    100005    3   udp    967  mountd
    100005    1   tcp    967  mountd
    100005    3   tcp    967  mountd
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100003    2   tcp   2049  nfs
    100003    3   tcp   2049  nfs
    100024    1   udp    689  status
    100024    1   tcp    689  status
    100021    0   udp    616  nlockmgr
    100021    0   tcp    927  nlockmgr
    100021    1   udp    616  nlockmgr
    100021    1   tcp    927  nlockmgr
    100021    3   udp    616  nlockmgr
    100021    3   tcp    927  nlockmgr
    100021    4   udp    616  nlockmgr
    100021    4   tcp    927  nlockmgr

Output of mount on the Mac OS X 10.7.5 client:

/dev/disk1s2 on / (hfs, local)
devfs on /dev (devfs, local, nobrowse)
afp_0egBhf12TAP01SptRt47XSdj-3.2c000002 on /private/var/netboot (afpfs, nobrowse)
afp_0egBhf12TAP01SptRt47XSdj-4.2c000004 on /Network/Applications (afpfs, read-only)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
afp_0egBhf12TAP01SptRt47XSdj-4.2c000008 on /Network/Servers/chef.farcry.sitepalette.com/Users (afpfs, nodev, nosuid, automounted, nobrowse, mounted by jnet)
afp_0egBhf12TAP01SptRt47XSdj-4.2c000009 on /Volumes/Users (afpfs, nodev, nosuid, mounted by jnet)
10.100.1.2:/mnt/raid/netboot on /Volumes/netboot (nfs)

And finally, the output of /usr/bin/hdiutil attach -debug /Volumes/netboot/Lion.nbi/Library.dmg -notremovable -shadow /private/var/netboot/Library-Shadow -owners on -noverify -noautofsck -nobrowse:

calling DIHLDiskImageAttach with 
skip-verify: true
auto-fsck: false
drive-options:
quiet: false
shadow-url: file://localhost/private/var/netboot/Library-Shadow
mount-nobrowse: true
enable-owners: true
verbose: false
debug: true
agent: hdiutil
fixed-disk: true
image-options:
main-url: file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
2012-11-27 12:02:23.053 hdiutil[23401:707] DIHLDiskImageAttach: input dictionary {
    agent = hdiutil;
    "auto-fsck" = 0;
    debug = 1;
    "drive-options" =     {
    };
    "enable-owners" = 1;
    "fixed-disk" = 1;
    "image-options" =     {
    };
    "main-url" = "file://localhost/Volumes/netboot/Lion.nbi/Library.dmg";
    "mount-nobrowse" = 1;
    quiet = 0;
    "shadow-url" = "file://localhost/private/var/netboot/Library-Shadow";
    "skip-verify" = 1;
    verbose = 0;
}
2012-11-27 12:02:23.054 hdiutil[23401:707] DIHLDiskImageAttach: disabling legacy image format attach
2012-11-27 12:02:23.055 hdiutil[23401:707] DIHLDiskImageAttach: newImagekeys = {
    "legacy-disabled" = 1;
}
2012-11-27 12:02:23.055 hdiutil[23401:707] DIHLDiskImageAttach: creating DIHelperProxy
2012-11-27 12:02:23.056 hdiutil[23401:707] with dictionary: {
    agent = hdiutil;
    "auto-fsck" = 0;
    debug = 1;
    "drive-options" = <62706c69 73743030 d0080000 00000000 01010000 00000000 00010000 00000000 00000000 00000000 0009>;
    "enable-owners" = 1;
    "fixed-disk" = 1;
    "image-options" = <62706c69 73743030 d101025f 100f6c65 67616379 2d646973 61626c65 6409080b 1d000000 00000001 01000000 00000000 03000000 00000000 00000000 00000000 1e>;
    "main-url" = "file://localhost/Volumes/netboot/Lion.nbi/Library.dmg";
    "mount-nobrowse" = 1;
    operation = DIHelperAttach;
    quiet = 0;
    "shadow-url" = "file://localhost/private/var/netboot/Library-Shadow";
    "skip-verify" = 1;
    verbose = 0;
}
2012-11-27 12:02:23.056 hdiutil[23401:707] [DIHelperProxy alloc]
2012-11-27 12:02:23.056 hdiutil[23401:707] [DIHelperProxy alloc] returning self 0x7fa39b00d690, retainCount 1
2012-11-27 12:02:23.057 hdiutil[23401:707] DIHLDiskImageAttach: running DIHelperProxy
2012-11-27 12:02:23.057 hdiutil[23401:707] [DIHelperProxy performOperationReturning] entry
2012-11-27 12:02:23.057 hdiutil[23401:707] [DIHelperProxy performOperationReturning] detaching thread
2012-11-27 12:02:23.058 hdiutil[23401:2803] [DIHelperProxy workerThread] entry
2012-11-27 12:02:23.058 hdiutil[23401:2803] [DIHelperProxy workerThread] setting up server
2012-11-27 12:02:23.059 hdiutil[23401:2803] [DIHelperProxy threadSetupServer] entry
2012-11-27 12:02:23.059 hdiutil[23401:2803] [DIHelperProxy threadSetupServer] setting up _headerConnection
2012-11-27 12:02:23.060 hdiutil[23401:2803] [DIHelperProxy threadSetupServer] setting up _headerConnection rootObject
2012-11-27 12:02:23.060 hdiutil[23401:2803] [DIHelperProxy threadSetupServer] adding NSConnectionDidInitializeNotification notification
2012-11-27 12:02:23.061 hdiutil[23401:2803] [DIHelperProxy threadSetupServer] exiting
2012-11-27 12:02:23.061 hdiutil[23401:2803] [DIHelperProxy workerThread] launching
2012-11-27 12:02:23.061 hdiutil[23401:2803] [DIHelperProxy threadLaunchToolAuthenticated] entry
2012-11-27 12:02:23.063 hdiutil[23401:2803] launching helper tool at "/System/Library/PrivateFrameworks/DiskImages.framework/Resources/diskimages-helper".
2012-11-27 12:02:23.063 hdiutil[23401:2803] [DIHelperProxy threadLaunchToolAuthenticated] adding NSTaskDidTerminateNotification notification
2012-11-27 12:02:23.063 hdiutil[23401:2803] [DIHelperProxy thread LaunchToolAuthenticated] launching
2012-11-27 12:02:23.065 hdiutil[23401:2803] [DIHelperProxy threadLaunchToolAuthenticated] exiting
2012-11-27 12:02:23.065 hdiutil[23401:2803] [DIHelperProxy workerThread] running runloop
2012-11-27 12:02:23.081 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] entry
2012-11-27 12:02:23.081 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] adding new NSConnectionDidDieNotification notification
2012-11-27 12:02:23.081 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] removing old NSConnectionDidDieNotification notification
2012-11-27 12:02:23.082 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] removing old connection rootObject
2012-11-27 12:02:23.082 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] invalidating old connection
2012-11-27 12:02:23.083 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] releasing old connection
2012-11-27 12:02:23.083 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] and replacing with new connection
2012-11-27 12:02:23.083 hdiutil[23401:2803] [DIHelperProxy helperConnectionInitialized] exit
2012-11-27 12:02:23.085 hdiutil[23401:2803] [DIHelperProxy connectToFramework] entry, helper 0x7fa39b016940
2012-11-27 12:02:23.085 hdiutil[23401:2803] [DIHelperProxy connectToFramework] exit
2012-11-27 12:02:23.186 hdiutil[23401:2803] [DIHelperProxy sendOperationToHelper] entry
2012-11-27 12:02:23.187 hdiutil[23401:2803] [DIHelperProxy sendOperationToHelper] starting operation with helper
2012-11-27 12:02:23.190 hdiutil[23401:2803] [DIHelperProxy sendOperationToHelper] exit
2012-11-27 12:02:23.194 hdiutil[23401:2803] [DIHelperProxy frameworkCallbackWithDictionary] entry
status proc called: initialize
Initializing…
myStatusProc: returning 0 
2012-11-27 12:02:23.199 hdiutil[23401:2803] [DIHelperProxy frameworkCallbackWithDictionary] exit
2012-11-27 12:02:23.201 diskimages-helper[23407:2503] updateImageAndDriveDictionaries: before update _imageOptions: {
    "enable-keychain" = 1;
    writeable = 0;
}
2012-11-27 12:02:23.201 diskimages-helper[23407:2503] updateImageAndDriveDictionaries: _imageOptions: {
    "enable-keychain" = 1;
    "legacy-disabled" = 1;
    writeable = 0;
}
2012-11-27 12:02:23.202 diskimages-helper[23407:2503] _driveOptions: {
    "auto-fsck" = 0;
    autodiskmount = 1;
    removable = 0;
    "unmount-timeout" = 0;
}
2012-11-27 12:02:23.202 diskimages-helper[23407:2503] DIHelperAttach: performOperation: initializing framework
2012-11-27 12:02:23.202 diskimages-helper[23407:2503] {
    agent = hdiutil;
    "auto-fsck" = 0;
    "auto-fsck-failure-override-type" = callback;
    "auto-open-ro-root" = 0;
    "auto-open-rw-root" = 0;
    "auto-stretch" = 0;
    "bundlebs-checkpointing" = 0;
    "bundlebs-localcloseonflush" = 0;
    "bundlebs-localcloseonidle" = 0;
    "bundlebs-localcloseonsleep" = 0;
    "bundlebs-localfdcount" = 6;
    "bundlebs-remotecloseonflush" = 0;
    "bundlebs-remotecloseonidle" = 0;
    "bundlebs-remotecloseonsleep" = 0;
    "bundlebs-remotefdcount" = 3;
    "burn-apple-supported-devices-only" = 0;
    "burn-no-underrun-protection" = 0;
    "burn-synthesize-content" = 1;
    "bzip2-level" = 0;
    "callback-with-sla" = 1;
    debug = 1;
    "disable-encrypted-images" = 0;
    "disable-kernel-mounting" = 1;
    "disable-owners" = 0;
    "drive-options" = <62706c69 73743030 d0080000 00000000 01010000 00000000 00010000 00000000 00000000 00000000 0009>;
    "enable-owners" = 1;
    "filevault-default-case-sensitive-file-system" = "Case-sensitive Journaled HFS+";
    "filevault-default-encryption-type" = "AES-128";
    "filevault-default-file-system" = "Journaled HFS+";
    "filevault-default-image-type" = SPARSEBUNDLE;
    "filevault-default-partition-type" = SPUD;
    "filevault-default-volume-name" = FileVault;
    "fixed-disk" = 1;
    "force-idme" = 0;
    "hfsplus-stretch-parameters" =     {
        "hfsplus-stretch-allocation-block-size" = 4096;
        "hfsplus-stretch-allocation-file-size" = 8388608;
        "hfsplus-stretch-threshold" = 524288;
    };
    "idle-timeout" = 15;
    "ifd-format" = UDZO;
    "ifd-ignore-io-errors" = 1;
    "ifd-segment-size" = 0;
    "iff-format" = UDZO;
    "iff-fs" = "HFS+";
    "iff-layout" = SPUD;
    "iff-source-owners" = auto;
    "iff-spotlight-indexing" = 0;
    "iff-temp-sparse-band-size" = 20480;
    "iff-temp-use-rw-if-possible" = 1;
    "iff-usehelper" = 1;
    "ignore-bad-checksums" = 0;
    "image-options" = <62706c69 73743030 d101025f 100f6c65 67616379 2d646973 61626c65 6409080b 1d000000 00000001 01000000 00000000 03000000 00000000 00000000 00000000 1e>;
    "main-url" = "file://localhost/Volumes/netboot/Lion.nbi/Library.dmg";
    "mount-attempted" = 1;
    "mount-nobrowse" = 1;
    "mount-point" = "/Volumes/";
    "mount-private" = 0;
    "mount-required" = 1;
    "mount-type" = in;
    "nbi-spotlight-indexing" = 0;
    operation = DIHelperAttach;
    "progress-delay" = 5;
    "pthread-reader-cap" = 4;
    quiet = 0;
    "reauthenticate-upon-wake" = 1;
    "shadow-url" = "file://localhost/private/var/netboot/Library-Shadow";
    "skip-auto-fsck-for-system-images" = 1;
    "skip-idme" = 1;
    "skip-idme-reveal" = 0;
    "skip-idme-trash" = 0;
    "skip-previously-verified" = 1;
    "skip-sla" = 0;
    "skip-verify" = 1;
    "skip-verify-locked" = 0;
    "skip-verify-remote" = 1;
    "sparsebundle-compactonidle" = 0;
    "suppress-uiagent" = 1;
    "unmount-timeout" = 0;
    "use-compressed-xml" = 0;
    "use-keychain" = 1;
    verbose = 0;
    "zlib-level" = 1;
}
DILoadDriver: checking for disk image driver
DILoadDriver: DI_kextExists() returned 0x00000000 (0)
DIIsInitialized: returning NO
2012-11-27 12:02:23.206 diskimages-helper[23407:2503] -checkForPreviouslyAttachedImage: entry
2012-11-27 12:02:23.206 diskimages-helper[23407:2503] imageURL file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
2012-11-27 12:02:23.206 diskimages-helper[23407:2503] shadowURL file://localhost/private/var/netboot/Library-Shadow
2012-11-27 12:02:23.207 diskimages-helper[23407:2503] sectionStart (null) sectionLength (null)
2012-11-27 12:02:23.207 diskimages-helper[23407:2503] checkForPreviouslyAttachedImage: setting legacy-disabled to 1
DIIsInitialized: returning YES
DIBackingStoreNewWithCFURL: entry with
file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
skip-permissions-check: true
legacy-disabled: true
DIBackingStoreInstantiatorProbe: entry
file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
skip-permissions-check: true
legacy-disabled: true
DIBackingStoreInstantiatorProbe: probing interface 0 CBSDBackingStore
CBSDBackingStore::newProbe score 100 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 1 CBundleBackingStore
CBundleBackingStore::newProbe score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 2 CRAMBackingStore
CRAMBackingStore::probe: scheme "file": not ram: or ramdisk: scheme.
CRAMBackingStore::probe: score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 3 CCarbonBackingStore
CCarbonBackingStore::newProbe: setting initial rval to +100
CCarbonBackingStore::newProbe score 100 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 4 CDevBackingStore
CDevBackingStore::newProbe: not /dev/disk or /dev/rdisk (/Volumes/netboot/Lion.nbi/Library.dmg).CDevBackingStore::newProbe score -1000 for 
DIBackingStoreInstantiatorProbe: probing interface 5 CCURLBackingStore
CCURLBackingStore::probe: scheme is: file
CCURLBackingStore::probe: not recognized URL scheme.
CCURLBackingStore::probe: score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 6 CVectoredBackingStore
CVectoredBackingStore::newProbe not "vectored" scheme.
CVectoredBackingStore::newProbe score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: selecting CBSDBackingStore
DIBackingStoreNewWithCFURL: CBSDBackingStore
CBSDBackingStore::setNoFollow: setting _noFollow to 0
DIBackingStoreNewWithCFURL: instantiator returned 0
DIBackingStoreNewWithCFURL: returning 0
2012-11-27 12:02:23.208 diskimages-helper[23407:2503] -checkForPreviouslyAttachedImage: resolving file://localhost/Volumes/netboot/Lion.nbi/Library.dmg returned 0
DIIsInitialized: returning YES
DIBackingStoreNewWithCFURL: entry with
file://localhost/private/var/netboot/Library-Shadow
skip-permissions-check: true
DIBackingStoreInstantiatorProbe: entry
file://localhost/private/var/netboot/Library-Shadow
skip-permissions-check: true
DIBackingStoreInstantiatorProbe: probing interface 0 CBSDBackingStore
CBSDBackingStore::newProbe score 1 for file://localhost/private/var/netboot/Library-Shadow
DIBackingStoreInstantiatorProbe: probing interface 1 CBundleBackingStore
CBundleBackingStore::newProbe score -1000 for file://localhost/private/var/netboot/Library-Shadow
DIBackingStoreInstantiatorProbe: probing interface 2 CRAMBackingStore
CRAMBackingStore::probe: scheme "file": not ram: or ramdisk: scheme.
CRAMBackingStore::probe: score -1000 for file://localhost/private/var/netboot/Library-Shadow
DIBackingStoreInstantiatorProbe: probing interface 3 CCarbonBackingStore
CCarbonBackingStore::newProbe stat() failed.  No such file or directory.
CCarbonBackingStore::newProbe score -1000 for file://localhost/private/var/netboot/Library-Shadow
DIBackingStoreInstantiatorProbe: probing interface 4 CDevBackingStore
CDevBackingStore::newProbe: not /dev/disk or /dev/rdisk (/private/var/netboot/Library-Shadow).CDevBackingStore::newProbe score -1000 for 
DIBackingStoreInstantiatorProbe: probing interface 5 CCURLBackingStore
CCURLBackingStore::probe: scheme is: file
CCURLBackingStore::probe: not recognized URL scheme.
CCURLBackingStore::probe: score -1000 for file://localhost/private/var/netboot/Library-Shadow
DIBackingStoreInstantiatorProbe: probing interface 6 CVectoredBackingStore
CVectoredBackingStore::newProbe not "vectored" scheme.
CVectoredBackingStore::newProbe score -1000 for file://localhost/private/var/netboot/Library-Shadow
DIBackingStoreInstantiatorProbe: selecting CBSDBackingStore
DIBackingStoreNewWithCFURL: CBSDBackingStore
DIBackingStoreNewWithCFURL: instantiator returned 2
DIBackingStoreNewWithCFURL: returning 2
DIResolveURLToBackingStore: unable to resolve to any backing store class. 2. 
2012-11-27 12:02:23.208 diskimages-helper[23407:2503] -checkForPreviouslyAttachedImage: resolving shadow file://localhost/private/var/netboot/Library-Shadow returned 2
2012-11-27 12:02:23.208 diskimages-helper[23407:2503] DIHelperAttach: performOperation: resolving disk image
DIIsInitialized: returning YES
DIIsInitialized: returning YES
DIBackingStoreNewWithCFURL: entry with
file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
legacy-disabled: true
writeable: false
enable-keychain: true
image-path: /Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: entry
file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
legacy-disabled: true
writeable: false
enable-keychain: true
image-path: /Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 0 CBSDBackingStore
CBSDBackingStore::newProbe score 100 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 1 CBundleBackingStore
CBundleBackingStore::newProbe score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 2 CRAMBackingStore
CRAMBackingStore::probe: scheme "file": not ram: or ramdisk: scheme.
CRAMBackingStore::probe: score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 3 CCarbonBackingStore
CCarbonBackingStore::newProbe: setting initial rval to +100
CCarbonBackingStore::newProbe score 100 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 4 CDevBackingStore
CDevBackingStore::newProbe: not /dev/disk or /dev/rdisk (/Volumes/netboot/Lion.nbi/Library.dmg).CDevBackingStore::newProbe score -1000 for 
DIBackingStoreInstantiatorProbe: probing interface 5 CCURLBackingStore
CCURLBackingStore::probe: scheme is: file
CCURLBackingStore::probe: not recognized URL scheme.
CCURLBackingStore::probe: score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: probing interface 6 CVectoredBackingStore
CVectoredBackingStore::newProbe not "vectored" scheme.
CVectoredBackingStore::newProbe score -1000 for file://localhost/Volumes/netboot/Lion.nbi/Library.dmg
DIBackingStoreInstantiatorProbe: selecting CBSDBackingStore
DIBackingStoreNewWithCFURL: CBSDBackingStore
CBSDBackingStore::setPermission: opening /Volumes/netboot/Lion.nbi/Library.dmg
CBSDBackingStore::OpenLockFriendly: mapping flags 0x00000000 -> 0x00000014 (locks are MANDATORY)
CBSDBackingStore:OpenLockFriendly: could not open with lock 30
DIBackingStoreNewWithCFURL: instantiator returned 30
DIBackingStoreNewWithCFURL: returning 30
DIResolveURLToBackingStore: unable to resolve to any backing store class. 30. 
DIResolveURLToDiskImage: resolving backing store/file encoding failed. 30. 
2012-11-27 12:02:23.211 hdiutil[23401:2803] [DIHelperProxy frameworkCallbackWithDictionary] entry
status proc called: attach
Attaching…
Error 30 (Read-only file system).
myStatusProc: returning 0 
2012-11-27 12:02:23.227 hdiutil[23401:2803] [DIHelperProxy frameworkCallbackWithDictionary] exit
2012-11-27 12:02:23.228 hdiutil[23401:2803] [DIHelperProxy frameworkCallbackWithDictionary] entry
status proc called: cleanup
Finishing…
myStatusProc: returning 0 
2012-11-27 12:02:23.228 hdiutil[23401:2803] [DIHelperProxy frameworkCallbackWithDictionary] exit
2012-11-27 12:02:23.229 diskimages-helper[23407:2503] DIHelperAttach performOperation: returning 30
2012-11-27 12:02:23.229 diskimages-helper[23407:2503] -decrementBackgroundThreadCount: _backgroundThreadCount is now 0.
2012-11-27 12:02:23.229 diskimages-helper[23407:303] DIHelper _report_results: reporting {
    payload =     {
    };
    "result-code" = 30;
}
2012-11-27 12:02:23.230 hdiutil[23401:2803] reportResultsToFramework: proxy has finished operation
2012-11-27 12:02:23.230 hdiutil[23401:2803] reportResultsToFramework: results are: {
    payload =     {
    };
    "result-code" = 30;
}
2012-11-27 12:02:23.230 hdiutil[23401:2803] reportResultsToFramework: _threadResultsError is 30
2012-11-27 12:02:23.231 hdiutil[23401:2803] reportResultsToFramework: disconnecting from helper.
2012-11-27 12:02:23.231 diskimages-helper[23407:303] -setCanTerminate: main thread can exit
2012-11-27 12:02:23.332 hdiutil[23401:2803] [DIHelperProxy disconnectFromHelper] entry
2012-11-27 12:02:23.333 hdiutil[23401:2803] disconnectFromHelper: removing observers
2012-11-27 12:02:23.333 hdiutil[23401:2803] disconnectFromHelper: terminating proxy
2012-11-27 12:02:23.334 diskimages-helper[23407:303] DIHelper: terminateHelper: entry.
2012-11-27 12:02:23.334 hdiutil[23401:2803] disconnectFromHelper: terminated proxy
2012-11-27 12:02:23.335 hdiutil[23401:2803] [DIHelperProxy disconnectFromHelper] releasing helper
2012-11-27 12:02:23.335 hdiutil[23401:2803] [DIHelperProxy disconnectFromHelper] exit
2012-11-27 12:02:23.435 diskimages-helper[23407:303] [DIHelper frameworkConnectionDied] entry
2012-11-27 12:02:23.435 diskimages-helper[23407:303] [DIHelper frameworkConnectionDied] releasing connection
2012-11-27 12:02:23.435 diskimages-helper[23407:303] [DIHelper frameworkConnectionDied] releasing frameworkProxy
2012-11-27 12:02:23.435 diskimages-helper[23407:303] -DIHelperAgentMaster terminateUIAgentConnection.
2012-11-27 12:02:23.435 diskimages-helper[23407:303] [DIHelper frameworkConnectionDied] marking _frameworkDisconnected
2012-11-27 12:02:23.435 diskimages-helper[23407:303] [DIHelper frameworkConnectionDied] exiting
2012-11-27 12:02:24.232 hdiutil[23401:2803] [DIHelperProxy workerThread] removing NSConnectionDidDieNotification observers
2012-11-27 12:02:24.233 hdiutil[23401:2803] [DIHelperProxy workerThread] removing NSConnectionDidInitializeNotification observers
2012-11-27 12:02:24.234 hdiutil[23401:2803] [DIHelperProxy workerThread] removing NSTaskDidTerminateNotification observers
2012-11-27 12:02:24.234 hdiutil[23401:2803] [DIHelperProxy threadRunRunLoop] invalidating connection
2012-11-27 12:02:24.235 diskimages-helper[23407:303] DIHelper dealloc.
2012-11-27 12:02:24.234 hdiutil[23401:2803] [DIHelperProxy threadRunRunLoop] releasing connection
2012-11-27 12:02:24.235 diskimages-helper[23407:303] -DIHelperAgentMaster terminateUIAgentConnection.
2012-11-27 12:02:24.235 hdiutil[23401:2803] [DIHelperProxy workerThread] after running runloop
2012-11-27 12:02:24.235 diskimages-helper[23407:303] helper: child_after_exec returning 0
2012-11-27 12:02:24.235 hdiutil[23401:2803] [DIHelperProxy workerThread] waiting for task to terminate to avoid zombies
2012-11-27 12:02:24.236 hdiutil[23401:2803] [DIHelperProxy workerThread] releasing task
2012-11-27 12:02:24.236 hdiutil[23401:2803] [DIHelperProxy workerThread] exiting
2012-11-27 12:02:24.236 hdiutil[23401:707] [DIHelperProxy performOperationReturning] returning 30
2012-11-27 12:02:24.237 hdiutil[23401:707] DIHLDiskImageAttach: DIHelperProxy returned 30
2012-11-27 12:02:24.237 hdiutil[23401:707] [DIHelperProxy dealloc]
DIHLDiskImageAttach() returned 30
hdiutil: attach failed - Read-only file system
kyle:~ root# 
share|improve this question
1  
I don't have an NFS share to test with, but I would try to have a quiet system and run fs_usage to see if I can catch the filesystem making a write call - possibly filing a bug with Apple. It seems you should be able to read a read-only DMG - but perhaps there is some deeper technical reason why it's failing and the OS needs a better error message to inform us why... –  bmike Nov 21 '12 at 15:04
    
Good idea @bmike! Also, I ran hdiutil with the -debug switch, I can post those logs here –  Josh Nov 21 '12 at 15:05
    
Indeed - make an answer with whatever you find and we can team up - report a bug or edit the answer as we pick apart the "why". –  bmike Nov 21 '12 at 15:17
    
Which OS runs on the NFS server? What is the output of rpcinfo -p on the server? What is the output of mount on your Mac? Can you also add the relevant line of /etc/exports on the NFS server to the question? –  jaume Nov 22 '12 at 9:04
1  
I've set up an NFS server (Ubuntu 12.04) with a read-only export that I mounted on my Mac (OS X 10.8.2) and I couldn't reproduce your problem (I tested all dmg formats: readonly, compressed, encrypted, etc)... Could you add the output of hdiutil -debug and the information I asked for to your question? –  jaume Nov 23 '12 at 21:07
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2 Answers 2

up vote 10 down vote accepted
+50

I've been interested in this question since Nov 2012 and even set up a FreeNAS VM to reproduce the issue.

I eventually gave up but since the question has been resuscitated I will share what I found out back then and in the last hours (luckily I didn't delete the VM) and what I think the cause for this issue is. I have also found a workaround.

My setup

First of all, this is my test setup:

  • OS X 10.8.2 (sorry, no 10.7.5 around).

  • FreeNAS (FreeBSD 8.2-RELEASE-p1)

    enter image description here

    (The OP's version is FreeBSD 8.2-RELEASE-p7 - I couldn't find the same version.)

  • A NAS filesystem in /mnt/raid:

    enter image description here

  • A user named netboot:

    enter image description here

  • An AFP filesystem (/mnt/raid/netboot) exported as netboot:

    enter image description here

    (Note that it is configured read-only).

  • An NFS filesystem (same path as AFP filesystem, to match the OP's configuration: /mnt/raid/netboot):

    enter image description here

AFP works, NFS doesn't

I mounted the AFP read-only filesystem as user netboot using the Finder with K:

enter image description here

and mounted a DMG image file without any problems:

$ sudo rm /private/var/netboot/Library-Shadow
$ sudo /usr/bin/hdiutil attach /Volumes/netboot/p7zip-9.04-0.i386.dmg -notremovable -shadow /private/var/netboot/Library-Shadow -owners on -noverify -noautofsck -nobrowse
Password:
/dev/disk3              Apple_partition_scheme          
/dev/disk3s1            Apple_partition_map             
/dev/disk3s2            Apple_HFS                       /Volumes/p7zip.pkg

Then I unmounted it and mounted the read-only NFS filesystem (I also used K) and couldn't mount the DMG image file.

I think the problem is logged here:

CBSDBackingStore::setPermission: opening /Volumes/netboot/Lion.nbi/Library.dmg
CBSDBackingStore::OpenLockFriendly: mapping flags 0x00000000 -> 0x00000014 (locks are MANDATORY)
CBSDBackingStore:OpenLockFriendly: could not open with lock 30

Error 30 means (see man 2 intro):

30 EROFS Read-only file system. An attempt was made to modify a file or directory was made on a file system that was read-only at the time.

No surprise here, it is indeed a read-only filesystem, but... when mounted over AFP it works, why?

Because Apple's NFS implementation has some problems with locking. As stated in this post at gluster.org:

OS X does a phenominal amount of file locking (some would say, needlessly so) and has always been really sensitive to the configuration of locking on the NFS servers. So much so that if you randomly pick an NFS server in a large enterprise, true success is pretty unlikely.

In my setup, the NFS server (that is, the FreeNAS VM) was suddenly irresponsive (from my Mac's /var/log/system.log):

Mar 15 15:35:04 avallone.local rpc.lockd[8119]: Lockd got unexpected signal 20
Mar 15 15:35:04 avallone com.apple.launchd[1] (com.apple.lockd[8119]): Exited with code: 1
Mar 15 15:35:04 avallone com.apple.launchd[1] (com.apple.lockd): Throttling respawn: Will start in 10 seconds
(...)
Mar 15 15:35:07 avallone com.apple.launchd[1] (com.apple.statd[8121]): Exited with code: 1
Mar 15 15:35:07 avallone com.apple.launchd[1] (com.apple.statd): Throttling respawn: Will start in 10 seconds
Mar 15 15:35:13 avallone kernel[0]: nfs server 172.16.54.186:/mnt/raid/netboot: lockd not responding
Mar 15 15:35:13 avallone.local KernelEventAgent[72]: tid 00000000 received event(s) VQ_NOTRESP (1)
Mar 15 15:35:13 avallone.local KernelEventAgent[72]: tid 00000000 type 'nfs', mounted on '/Volumes/netboot', from '172.16.54.186:/mnt/raid/netboot', not responding
(...)
Mar 15 15:35:34 avallone.local KernelEventAgent[72]: tid 00000000 unmounting 1 filesystems

The output of sudo /usr/bin/hdiutil attach -debug /Volumes/netboot/p7zip-9.04-0.i386.dmg -notremovable -shadow /private/var/netboot/Library-Shadow -owners on -noverify -noautofsck -nobrowse was:

CBSDBackingStore::setPermission: opening /Volumes/netboot/p7zip-9.04-0.i386.dmg
CBSDBackingStore::OpenLockFriendly: mapping flags 0x00000000 -> 0x00000014 (locks are MANDATORY)
CBSDBackingStore:OpenLockFriendly: could not open with lock 5

Error 5 means (again from man 2 intro):

5 EIO Input/output error. Some physical input or output error occurred. This error will not be reported until a subsequent operation on the same file descriptor and may be lost (over written) by any subsequent errors.

which isn't suprising at all, the NFS filesystem was gone.

Workaround

A workaround (tested on OS X 10.8) is to mount NFS with options nolocks,locallocks. As explained in the post at gluster.org already mentioned:

Fortunately, there is a fix: just turn off network locking. You can do it by adding the "nolocks,locallocks" options in the advanced options field of the Disk Utility NFS mounting UI, but this is painful if you do a lot of them, and doesn't help at all with /net. You can edit /etc/auto_master to add these options to the /net entry, but it doesn't affect other mounts - however I do recommend deleting the hidefromfinder option in auto_master. If you want to fix every automount, edit /etc/autofs.conf and search for the line that starts with AUTOMOUNTD_MNTOPTS=. These options get applied on every mount. Add nolocks,locallocks and your world will be faster and happier after you reboot.

I manually mounted 172.16.54.186:/mnt/raid/netboot and it worked flawlessly:

$ sudo rm /private/var/netboot/Library-Shadow
$ sudo mount -o nolocks,locallocks,ro 172.16.54.186:/mnt/raid/netboot /tmp/mnt
$ sudo /usr/bin/hdiutil attach /tmp/mnt/p7zip-9.04-0.i386.dmg -notremovable -shadow /private/var/netboot/Library-Shadow -owners on -noverify -noautofsck -nobrowse
/dev/disk6              Apple_partition_scheme          
/dev/disk6s1            Apple_partition_map             
/dev/disk6s2            Apple_HFS                       /Volumes/p7zip.pkg

I also edited /etc/auto_master like this:

+auto_master # Use directory service
#/net             -hosts    -nobrowse,hidefromfinder,nosuid
/net              -hosts    -nosuid,nolocks,locallocks
/home             auto_home -nobrowse,hidefromfinder
/Network/Servers  -fstab
/-                -static

stopped and started automountd and autofsd:

$ sudo launchctl unload /System/Library/LaunchDaemons/com.apple.automountd.plist 
$ sudo launchctl unload /System/Library/LaunchDaemons/com.apple.autofsd.plist 
$ sudo launchctl load /System/Library/LaunchDaemons/com.apple.autofsd.plist 
$ sudo launchctl load /System/Library/LaunchDaemons/com.apple.automountd.plist 

and worked like a charm:

$ cd /net/172.16.54.186/mnt/raid/netboot
$ ls 
Network Trash Folder  Temporary Items  p7zip-9.04-0.i386.dmg
$ sudo rm /private/var/netboot/Library-Shadow
$ sudo /usr/bin/hdiutil attach p7zip-9.04-0.i386.dmg -notremovable -shadow /private/var/netboot/Library-Shadow -owners on -noverify -noautofsck -nobrowse
/dev/disk7              Apple_partition_scheme          
/dev/disk7s1            Apple_partition_map             
/dev/disk7s2            Apple_HFS                       /Volumes/p7zip.pkg
share|improve this answer
    
Awesome, what a good read. –  gosmond Mar 15 '13 at 17:05
    
Wow this is fantastic, Thanks! I will test this over the weekend, it might solve my issue! –  Josh Mar 15 '13 at 17:05
    
Thanks jaume, this worked like a charm! Unfortunately I have already found an alternative and no longer need to mount this same DMG with a shadow file, but nolocks,locallocks is helping NFS performance of other read-only NFS shares with DMG files, so thank you! –  Josh Mar 16 '13 at 12:49
    
Thanks for your feedback, I'm happy the workaround worked in your environment. Although you don't need it anymore, it's nice to know why something doesn't work, isn't it? –  jaume Mar 18 '13 at 9:56
    
Absolutely, and now I know what I need to change should I need this again in the future! (The goal previously was to place the /Library of our NetBoot image n a RAID array. We no longer need this as we purchased a new Mac Pro server) –  Josh Mar 18 '13 at 13:18
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hdiutil attach -readonly …

For an image that's stored on a read-only file system, I reckon that -readonly should be used at time of attachment.

(The AFP case may be exceptional.)


Considering the down vote and the comment from @Josh: I misunderstood the -shadow part of the man page for hdiutil:

… allows read-only images to be attached read/write …

– I imagined that -shadow could override -readonly.

share|improve this answer
    
No, you misunderstand. I wanted to attache a read-only image as a read-write volume with a shadow file. –  Josh Mar 17 '13 at 18:14
1  
Regarding your edit, no, using both -readonly and -shadow would read from a shadow file but mount the image read-only. So for example it would allow you to read changes made to a shadow file without updating that shadow file. The issue was NFS locks as jaume discovered. –  Josh Mar 18 '13 at 13:17
    
A very neat explanation from @Josh – thanks! I'll leave this answer so that other readers don't make the same mistake as me. –  Graham Perrin Mar 19 '13 at 3:10
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