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Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 8:51 pm
by ElEscalador
I have a Pi running on a 16gb card and I like to back up entire images to Dropbox... This is what I seen in Gparted - what are the correct things to click so this would fit on an 8GB sd card? I get a warning if I try to shrink the big partition root0. (Ideally it'd be a bit smaller than 8GB- I learned the hard way that an image of an 8GB sd card won't always fit on other cards. I'd like to not have to worry about that.)
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 9:13 pm
by B.Goode
Side-stepping your question a little, if you are running a recent version of Raspbian Jessie you have access to an SD Card Copier (PiClone) which I think is designed to make a backup that is as large as needed to capture all your data, but no bigger.
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 9:19 pm
by ElEscalador
B.Goode wrote:Side-stepping your question a little, if you are running a recent version of Raspbian Jessie you have access to an SD Card Copier (PiClone) which I think is designed to make a backup that is as large as needed to capture all your data, but no bigger.
Hmmm...does it? In this case I'm running an older version anyway, but even if I were - I've used the copier tool included with the Pixel releases and have not seen an option to create an .IMG file that I could then upload to dropbox for a rainy day - only the ability to make another actual card (which is great, but not what I'm hoping to do here). Have I missed something terribly simple and obvious? Wouldn't be the first time, lol.
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 9:30 pm
by B.Goode
My thinking was that if you can clone to a backup that is smaller than your 8G limit then you could easily make an image of that backup. If the clone is bigger than 8G chances are there is no scope for shrinking an image of it to make it smaller...
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 9:36 pm
by W. H. Heydt
As regards the initial problem...gparted will change the partition sizes, but the usual backup tools (win32diskimager and dd) copy the entire contents of the SD card, whether or not those blocks are part of a file system or not. It's the difference between a logical copy and a physical copy. You need a backup process that recognizes and uses partition allocation information.
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 9:55 pm
by B.Goode
W. H. Heydt wrote:As regards the initial problem...gparted will change the partition sizes, but the usual backup tools (win32diskimager and dd) copy the entire contents of the SD card, whether or not those blocks are part of a file system or not. It's the difference between a logical copy and a physical copy. You need a backup process that recognizes and uses partition allocation information.
And of course that limitation in the behaviour of physical backups is the reason why my suggested way forward will not work...
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 10:34 pm
by pcmanbob
Hi.
to make my image files as small as possible for backing up I use a script run on a ubuntu desktop pc , I actually run ubuntu server 12 on an old pc as it does not require much in the way of resources and I can just ssh in to it and use the command line.
so I copy my img file to the pc then run this script
Code: Select all
#!/bin/bash
IMG="$1"
if [[ -e $IMG ]]; then
P_START=$( fdisk -lu $IMG | grep Linux | awk '{print $2}' ) # Start of 2nd partition in 512 byte sectors
P_SIZE=$(( $( fdisk -lu $IMG | grep Linux | awk '{print $3}' ) * 1024 )) # Partition size in bytes
losetup /dev/loop2 $IMG -o $(($P_START * 512)) --sizelimit $P_SIZE
fsck -f /dev/loop2
resize2fs -M /dev/loop2 # Make the filesystem as small as possible
fsck -f /dev/loop2
P_NEWSIZE=$( dumpe2fs /dev/loop2 2>/dev/null | grep '^Block count:' | awk '{print $3}' ) # In 4k blocks
P_NEWEND=$(( $P_START + ($P_NEWSIZE * 8) + 1 )) # in 512 byte sectors
losetup -d /dev/loop2
echo -e "p\nd\n2\nn\np\n2\n$P_START\n$P_NEWEND\np\nW\n" | fdisk $IMG
I_SIZE=$((($P_NEWEND + 1) * 512)) # New image size in bytes
truncate -s $I_SIZE $IMG
else
echo "Usage: $0 filename"
fi
it shrinks the image file to a absolute smallest it can allowing just enough space for the system to boot.
once you copy the file to a new sd card and its booted the first thing you do is run raspi-config and expand the file system.
you run the script like this assuming script save with file name shrink-img-file.sh
Code: Select all
sudo ./shrink-img-file.sh name of file to shrink goes here.img
now this is not my work I got the script from a post on this very forum some time ago.
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Mon Jan 02, 2017 10:35 pm
by tpylkko
Are you trying to shrink a partition that is in use? I mean you appear to be using gparted on pi itself.
If so, you can get around this by not using the same pi. Shut it down and take out the card. Then use a linux laptop, another pi (or the same pi with another raspian card) or live dvd/usb boot a Windows laptop temporarily with gparted live disk. Insert the raspbian card. Then the partitions will be offline and unmounted. Shrink said partition and copy-paste all of them on a smaller card or whereever you want. Gparted allows you to copy paste entire partitions. Then full physical back up that smaller card to your cloud as an image file that you can write with windows. Or even simpler, just copy the partitions and later use gparted again to copy paste them back without having to create img file
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Tue Jan 03, 2017 5:24 pm
by ElEscalador
tpylkko wrote:Are you trying to shrink a partition that is in use? I mean you appear to be using gparted on pi itself.
If so, you can get around this by not using the same pi. Shut it down and take out the card. Then use a linux laptop, another pi (or the same pi with another raspian card) or live dvd/usb boot a Windows laptop temporarily with gparted live disk. Insert the raspbian card. Then the partitions will be offline and unmounted. Shrink said partition and copy-paste all of them on a smaller card or whereever you want. Gparted allows you to copy paste entire partitions. Then full physical back up that smaller card to your cloud as an image file that you can write with windows. Or even simpler, just copy the partitions and later use gparted again to copy paste them back without having to create img file
Ahh..may give that a shot. (But nope - you were looking at a shot of a card plugged into USB - operating off of another Pi.
Re: Help Using Gparted to Shrink Resulting .IMG File Size
Posted: Tue Jan 03, 2017 6:05 pm
by tpylkko
Ok. My bad. What error is it that you get then?
