TIP_Running_out_of_space_use_a_loopback_device

This article is part of the Tips & Tricks series.

Terminals / Shells • Network • X Window System • Portage • System • Filesystems • Kernel • Other

Code:

 # mkdir /mnt/windows 
 # mount -t smbfs //windows/linuxtmp /mnt/windows 
 # dd if=/dev/zero of=/mnt/windows/portage-loop seek=1k bs=1k count=1000000 
 # losetup /dev/loop1 /mnt/windows/portage-loop 
 # mkfs.ext3 /dev/loop1 
 # mount -t ext3 /dev/loop1 /var/tmp 
 # emerge xorg-x11 (or something big)
 # umount /var/tmp 
 # losetup -d /dev/loop1 
 # rm -f /mnt/windows/portage-loop 
 # umount /mnt/windows

This is performed:

mount the windows share
create an empty 1Gb file on that share
use that file for creating a loopback device
create ext3 filesystem on that device
mount that device under /var/tmp (place where portage emerges packages)

It's possible to make this operation go much faster on filesystems that support sparse files.

Follow the instructions as above, but replace the dd step with:

Code:

 # dd if=/dev/zero of=/mnt/windows/portage-loop bs=1M count=1  seek=1000

This will tell dd to write a zero at the 1000th 1 Megabyte block, making a 1000MB file filled with zeros, just as above. However, this method takes advantage of most filesystem's (including NTFS) support for what are known as sparse files. The FS allocates the files as being of a a certain size, but the empty allocated space is not written to the disk itself; rather the FS keeps track of what regions are empty and actually fills them on the disk as appropriate.

PLEASE NOTE! FAT32/vfat does NOT support sparse files!