commandlinefu.com is the place to record those command-line gems that you return to again and again.
You can sign-in using OpenID credentials, or register a traditional username and password.
Subscribe to the feed for:
It's common to want to split up large files and the usual method is to use split(1).
If you have a 10GiB file, you'll need 10GiB of free space.
Then the OS has to read 10GiB and write 10GiB (usually on the same filesystem).
This takes AGES.
The command uses a set of loop block devices to create fake chunks, but without making any changes to the file.
This means the file splitting is nearly instantaneous.
The example creates a 1GiB file, then splits it into 16 x 64MiB chunks (/dev/loop0 .. loop15).
Note: This isn't a drop-in replacement for using split. The results are block devices.
tar and zip won't do what you expect when given block devices.
These commands will work:
gzip -9 < /dev/loop6 > part6.gz
cat /dev/loop10 > /media/usb/part10.bin
You need to be root to do this. So check the command before running it.
You enter the same password for
Enter LUKS passphrase:
Enter passphrase for /dev/loopn:
You can then copy the .img file to somewhere else.
Loop it it with losetup -f IMAGENAME.img and then mount it with a file manager (eg nemo) or run mount /dev/loopn /media/mountfolder
Acts similar to a mounted flash drive