First you have to create an image file:
# dd if=/dev/zero of=./binary.img bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 10.3739 s, 101 MB/s
Then, you have to create a partition on it -- you can use whatever tool you want, fdisk
, parted
, gparted
, I prefer parted
, so:
# parted binary.img
You have to create a partition table first and then one big partition:
(parted) mktable
New disk label type? msdos
(parted) mkpartfs
WARNING: you are attempting to use parted to operate on (mkpartfs) a file system.
parted's file system manipulation code is not as robust as what you'll find in
dedicated, file-system-specific packages like e2fsprogs. We recommend
you use parted only to manipulate partition tables, whenever possible.
Support for performing most operations on most types of file systems
will be removed in an upcoming release.
Partition type? primary/extended? primary
File system type? [ext2]? fat32
Start? 1
End? 1049M
Now let's see:
(parted) print
Model: (file)
Disk /media/binary.img: 1049MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 1049kB 1049MB 1048MB primary fat32 lba
It looks good,
You want to enlarge it, so fist add some zeros to the image using dd:
# dd if=/dev/zero bs=1M count=400 >> ./binary.img
400+0 records in
400+0 records out
419430400 bytes (419 MB) copied, 2.54333 s, 165 MB/s
root:/media# ls -al binary.img
-rw-r--r-- 1 root root 1.4G Dec 26 06:47 binary.img
That added 400M to the image:
# parted binary.img
GNU Parted 2.3
Using /media/binary.img
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print
Model: (file)
Disk /media/binary.img: 1468MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 1049kB 1049MB 1048MB primary fat32 lba
As you can see, the size of the image is different (1468MB). Parted can also show you free space in the image. If you want to see it just type print free
instead of print
. Now you have to add the extra space to the filesystem:
(parted) resize 1
WARNING: you are attempting to use parted to operate on (resize) a file system.
parted's file system manipulation code is not as robust as what you'll find in
dedicated, file-system-specific packages like e2fsprogs. We recommend
you use parted only to manipulate partition tables, whenever possible.
Support for performing most operations on most types of file systems
will be removed in an upcoming release.
Start? [1049kB]?
End? [1049MB]? 1468M
and check it:
(parted) print
Model: (file)
Disk /media/binary.img: 1468MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 1049kB 1468MB 1467MB primary fat32 lba
Pretty nice. If you want to shrink it, just do similar thing:
(parted) resize 1
WARNING: you are attempting to use parted to operate on (resize) a file system.
parted's file system manipulation code is not as robust as what you'll find in
dedicated, file-system-specific packages like e2fsprogs. We recommend
you use parted only to manipulate partition tables, whenever possible.
Support for performing most operations on most types of file systems
will be removed in an upcoming release.
Start? [1049kB]?
End? [1468MB]? 500M
Now you can check if the partition is smaller:
(parted) print
Model: (file)
Disk /media/binary.img: 1468MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 1049kB 500MB 499MB primary fat32 lba
Yes, it is.
If you try to resize the partition when data is on it, you have to pay attention to the size of the data because when you shrink it too much, you will get an error:
Error: Unable to satisfy all constraints on the partition
After shrinking the file system, you also have to cut some of the file off. But this is tricky. You could take the value from parted 500M (END):
# dd if=./binary.img of=./binary.img.new bs=1M count=500
But this leaves some space at the end of the file. I'm not sure why, but the image works.
And there's one thing about mounting such image -- you have to know an offset to pass to the mount command. You can get the offset from, for instance, fdisk:
# fdisk -l binary.img
Disk binary.img: 1468 MB, 1468006400 bytes
4 heads, 32 sectors/track, 22400 cylinders, total 2867200 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000f0321
Device Boot Start End Blocks Id System
binary.img1 2048 2867198 1432575+ c W95 FAT32 (LBA)
2048 (start) x 512 (sector size) = 1048576 , so you have to use the following command in order to mount the image:
# mount -o loop,offset=1048576 binary.img /mnt
1
When you write "But this leaves some space at the end of the file. I'm not sure why, but the image works." I think that it is caused by the fact that you are using different units of measurement. In parted, you have 500MB (in parted 1MB is 1000 * 1000 bytes), so 500000000 bytes; in dd you copy 1Mx500=500M, where M stands for 1024*1024 bytes, so you copy 524288000 bytes. The difference should be the space you left at the end of the file. To fix, you could do with truncate as described here https://softwarebakery.com/shrinking-images-on-linux or change the units of meas. in parted or in dd
– ste – 2018-05-18T08:42:08.4071Now it's irrelevant to use
parted
withresize
: "Error: The resize command has been removed in parted 3.0" – Abdillah – 2019-03-16T09:34:18.367