LOFIADM(1M) Maintenance Commands LOFIADM(1M)

lofiadm
administer files available as block devices through lofi

lofiadm [-r] [-l] -a file [device]

lofiadm [-r] -c crypto_algorithm -a file [device]

lofiadm [-r] -c crypto_algorithm -k raw_key_file -a file [device]

lofiadm [-r] -c crypto_algorithm -T token_key -a file [device]

lofiadm [-r] -c crypto_algorithm -T token_key -k wrapped_key_file -a file [device]

lofiadm [-r] -c crypto_algorithm -e -a file [device]

lofiadm -C algorithm [-s segment_size] file

lofiadm -d file|device

lofiadm -U file

lofiadm [file|device]

lofiadm administers lofi, the loopback file driver. lofi allows a file to be associated with a block device. That file can then be accessed through the block device. This is useful when the file contains an image of some filesystem (such as a floppy or CD-ROM image), because the block device can then be used with the normal system utilities for mounting, checking or repairing filesystems. See fsck(1M) and mount(1M).

Use lofiadm to add a file as a loopback device, remove such an association, or print information about the current associations.

Encryption and compression options are mutually exclusive on the command line. Further, an encrypted file cannot be compressed later, nor can a compressed file be encrypted later.

In the global zone, lofiadm can be used on both the global zone devices and all devices owned by other non-global zones on the system.

If the command line flag, -l, is used while creating a loopack device, lofi will create a labeled loopback device, and will generate device links in /dev/{dsk,rdsk} directories for partitions or slices.

Before using these devices, users should create or verify partitioning by using partition management tools such as format(1M) and fdisk(1M). Once the device has been appropriately partitioned, the labeled device can be used as normal disk to create and mount file systems and to store data. Mappings created by lofiadm are not permanent and not persisted by the system. If power is lost or the system is rebooted, then the mappings will need to be created again.

The partition table requires space from the mapped file. lofi does not support converting previously created unlabeled loopback device images to labeled loopback devices. If an unlabeled device is used as a labeled device, writing to it will corrupt it.

The following options are supported:
file [device]
Add file as a block device.

If device is not specified, an available device is picked.

If device is specified, lofiadm attempts to assign it to file. device must be available or lofiadm will fail. The ability to specify a device is provided for use in scripts that wish to reestablish a particular set of associations. A device may not be specified when using a labeled lofi device.

{gzip | gzip-N | lzma}
Compress the file with the specified compression algorithm.

The gzip compression algorithm uses the same compression as the open-source gzip command. You can specify the gzip level by using the value gzip-N where N is 6 (fast) or 9 (best compression ratio). Currently, gzip, without a number, is equivalent to gzip-6 (which is also the default for the gzip command).

lzma stands for the LZMA (Lempel-Ziv-Markov) compression algorithm.

Note that you cannot write to a compressed file, nor can you mount a compressed file read/write.

file|device
Remove an association by file or device name, if the associated block device is not busy, and deallocates the block device.
This option should be used with -a option to create labeled loopback device. If created in local zone, the device has to be enabled in zone configuration.
If the -r option is specified before the -a option, the device will be opened read-only.
segment_size
The segment size to use to divide the file being compressed. segment_size can be an integer multiple of 512.
file
Uncompress a compressed file.

The following options are used when the file is encrypted:

crypto_algorithm
Select the encryption algorithm. The algorithm must be specified when encryption is enabled because the algorithm is not stored in the disk image.

If none of -e, -k, or -T is specified, lofiadm prompts for a passphrase, with a minimum length of eight characters, to be entered. The passphrase is used to derive a symmetric encryption key using PKCS#5 PBKD2.

raw_key_file | wrapped_key_file
Path to raw or wrapped symmetric encryption key. If a PKCS#11 object is also given with the -T option, then the key is wrapped by that object. If -T is not specified, the key is used raw.
token_key
The key in a PKCS#11 token to use for the encryption or for unwrapping the key file.

If -k is also specified, -T identifies the unwrapping key, which must be an RSA private key.

Generate an ephemeral symmetric encryption key.

The following operands are supported:
crypto_algorithm
One of: aes-128-cbc, aes-192-cbc, aes-256-cbc, des3-cbc, blowfish-cbc.
device
Display the file name associated with the block device device.

Without arguments, print a list of the current associations. Filenames must be valid absolute pathnames.

When a file is added, it is opened for reading or writing by root. Any restrictions apply (such as restricted root access over NFS). The file is held open until the association is removed. It is not actually accessed until the block device is used, so it will never be written to if the block device is only opened read-only.

Note that the filename may appear as "?" if it is not possible to resolve the path in the current context (for example, if it's an NFS path in a non-global zone).

file
Display the block device associated with file.
raw_key_file
Path to a file of the appropriate length, in bits, to use as a raw symmetric encryption key.
token_key
PKCS#11 token object in the format:

token_name:manufacturer_id:serial_number:key_label

All but the key label are optional and can be empty. For example, to specify a token object with only its key label MylofiKey, use -T :::MylofiKey.

wrapped_key_file
Path to file containing a symmetric encryption key wrapped by the RSA private key specified by -T.

See environ(5) for descriptions of the following environment variables that affect the execution of lofiadm : LC_CTYPE, LC_MESSAGES and NLSPATH.

The following exit values are returned:
0
Successful completion.
>0
An error occurred.

Example 1 Mounting an Existing CD-ROM Image
You should ensure that Solaris understands the image before creating the CD. lofi allows you to mount the image and see if it works.

This example mounts an existing CD-ROM image (sparc.iso), of the Red Hat 6.0 CD which was downloaded from the Internet. It was created with the mkisofs utility from the Internet.

Use lofiadm to attach a block device to it:

# lofiadm -a /home/mike_s/RH6.0/sparc.iso
/dev/lofi/1
    

lofiadm picks the device and prints the device name to the standard output. You can run lofiadm again by issuing the following command:

# lofiadm
Block Device     File                           Options
/dev/lofi/1      /home/mike_s/RH6.0/sparc.iso   -
    

Or, you can give it one name and ask for the other, by issuing the following command:

# lofiadm /dev/lofi/1
/home/mike_s/RH6.0/sparc.iso
    

Use the mount(1M) command to mount the image:

# mount -F hsfs -o ro /dev/lofi/1 /mnt
    

Check to ensure that Solaris understands the image:

# df -k /mnt
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/lofi/1           512418  512418       0   100%    /mnt
# ls /mnt
./            RedHat/       doc/          ls-lR         rr_moved/
../           TRANS.TBL     dosutils/     ls-lR.gz      sbin@
.buildlog     bin@          etc@          misc/         tmp/
COPYING       boot/         images/       mnt/          usr@
README        boot.cat*     kernels/      modules/
RPM-PGP-KEY   dev@          lib@          proc/
    

Solaris can mount the CD-ROM image, and understand the filenames. The image was created properly, and you can now create the CD-ROM with confidence.

As a final step, unmount and detach the images:

# umount /mnt
# lofiadm -d /dev/lofi/1
# lofiadm
Block Device             File             Options
    
Example 2 Mounting a Floppy Image
This is similar to the first example.

Using lofi to help you mount files that contain floppy images is helpful if a floppy disk contains a file that you need, but the machine which you are on does not have a floppy drive. It is also helpful if you do not want to take the time to use the dd command to copy the image to a floppy.

This is an example of getting to MDB floppy for Solaris on an x86 platform:

# lofiadm -a /export/s28/MDB_s28x_wos/latest/boot.3
/dev/lofi/1
# mount -F pcfs /dev/lofi/1 /mnt
# ls /mnt
./            COMMENT.BAT*  RC.D/         SOLARIS.MAP*
../           IDENT*        REPLACE.BAT*  X/
APPEND.BAT*   MAKEDIR.BAT*  SOLARIS/
# umount /mnt
# lofiadm -d /export/s28/MDB_s28x_wos/latest/boot.3
    
Example 3 Making a UFS Filesystem on a File
Making a UFS filesystem on a file can be useful, particularly if a test suite requires a scratch filesystem. It can be painful (or annoying) to have to repartition a disk just for the test suite, but you do not have to. You can newfs a file with lofi.

Create the file:

# mkfile 35m /export/home/test
    

Attach it to a block device. You also get the character device that newfs requires, so newfs that:

# lofiadm -a /export/home/test
/dev/lofi/1
# newfs /dev/rlofi/1
newfs: construct a new file system /dev/rlofi/1: (y/n)? y
/dev/rlofi/1:   71638 sectors in 119 cylinders of 1 tracks, 602 sectors
        35.0MB in 8 cyl groups (16 c/g, 4.70MB/g, 2240 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
 32, 9664, 19296, 28928, 38560, 48192, 57824, 67456,
    

Note that ufs might not be able to use the entire file. Mount and use the filesystem:

# mount /dev/lofi/1 /mnt
# df -k /mnt
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/lofi/1            33455       9   30101     1%    /mnt
# ls /mnt
./           ../          lost+found/
# umount /mnt
# lofiadm -d /dev/lofi/1
    
Example 4 Creating a PC (FAT) File System on a Unix File
The following series of commands creates a FAT file system on a Unix file. The file is associated with a block device created by lofiadm
# mkfile 10M /export/test/testfs
# lofiadm -a /export/test testfs
/dev/lofi/1
    

Note use of rlofi, not lofi, in following command.

# mkfs -F pcfs -o nofdisk,size=20480 /dev/rlofi/1
Construct a new FAT file system on /dev/rlofi/1: (y/n)? y
# mount -F pcfs /dev/lofi/1 /mnt
# cd /mnt
# df -k .
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/lofi/1            10142       0   10142     0%    /mnt
    
Example 5 Compressing an Existing CD-ROM Image
The following example illustrates compressing an existing CD-ROM image (solaris.iso), verifying that the image is compressed, and then uncompressing it.
# lofiadm -C gzip /export/home/solaris.iso
    

Use lofiadm to attach a block device to it:

# lofiadm -a /export/home/solaris.iso
  /dev/lofi/1
    

Check if the mapped image is compressed:

# lofiadm
Block Device      File                            Options
/dev/lofi/1       /export/home/solaris.iso        Compressed(gzip)
/dev/lofi/2       /export/home/regular.iso        -
    

Unmap the compressed image and uncompress it:

# lofiadm -d /dev/lofi/1
# lofiadm -U /export/home/solaris.iso
    
Example 6 Creating an Encrypted UFS File System on a File
This example is similar to the example of making a UFS filesystem on a file, above.

Create the file:

# mkfile 35m /export/home/test
    

Attach the file to a block device and specify that the file image is encrypted. As a result of this command, you obtain the character device, which is subsequently used by newfs:

# lofiadm -c aes-256-cbc -a /export/home/secrets
Enter passphrase: My-M0th3r;l0v3s_m3+4lw4ys!           (not echoed)
Re-enter passphrase: My-M0th3r;l0v3s_m3+4lw4ys!        (not echoed)
/dev/lofi/1

# newfs /dev/rlofi/1
newfs: construct a new file system /dev/rlofi/1: (y/n)? y
/dev/rlofi/1:   71638 sectors in 119 cylinders of 1 tracks, 602 sectors
       35.0MB in 8 cyl groups (16 c/g, 4.70MB/g, 2240 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
32, 9664, 19296, 28928, 38560, 48192, 57824, 67456,
    

The mapped file system shows that encryption is enabled:

# lofiadm
Block Device    File                     Options
/dev/lofi/1     /export/home/secrets     Encrypted
    

Mount and use the filesystem:

# mount /dev/lofi/1 /mnt
# cp moms_secret_*_recipe /mnt
# ls /mnt
./         moms_secret_cookie_recipe    moms_secret_soup_recipe
../        moms_secret_fudge_recipe     moms_secret_stuffing_recipe
lost+found/  moms_secret_meatloaf_recipe  moms_secret_waffle_recipe
# umount /mnt
# lofiadm -d /dev/lofi/1
    

Subsequent attempts to map the filesystem with the wrong key or the wrong encryption algorithm will fail:

# lofiadm -c blowfish-cbc -a /export/home/secrets
Enter passphrase: mommy                                (not echoed)
Re-enter passphrase: mommy                             (not echoed)
lofiadm: could not map file /root/lofi: Invalid argument
# lofiadm
Block Device    File                    Options
#
    

Attempts to map the filesystem without encryption will succeed, however attempts to mount and use the filesystem will fail:

# lofiadm -a /export/home/secrets
/dev/lofi/1
# lofiadm
Block Device    File                     Options
/dev/lofi/1     /export/home/secrets     -
# mount /dev/lofi/1 /mnt
mount: /dev/lofi/1 is not this fstype
#
    

fdisk(1M), format(1M), fsck(1M), mount(1M), mount_ufs(1M), newfs(1M), attributes(5), lofi(7D), lofs(7FS)

Just as you would not directly access a disk device that has mounted file systems, you should not access a file associated with a block device except through the lofi file driver. It might also be appropriate to ensure that the file has appropriate permissions to prevent such access.

The abilities of lofiadm , and who can use them, are controlled by the permissions of /dev/lofictl. Read-access allows query operations, such as listing all the associations. Write-access is required to do any state-changing operations, like adding an association. As shipped, /dev/lofictl is owned by root, in group sys, and mode 0644, so all users can do query operations but only root can change anything. The administrator can give users write-access, allowing them to add or delete associations, but that is very likely a security hole and should probably only be given to a trusted group.

When mounting a filesystem image, take care to use appropriate mount options. In particular, the nosuid mount option might be appropriate for UFS images whose origin is unknown. Also, some options might not be useful or appropriate, like logging or forcedirectio for UFS. For compatibility purposes, a raw device is also exported along with the block device. For example, newfs(1M) requires one.

The output of lofiadm (without arguments) might change in future releases.

June 14, 2016 OmniOS