Learn the UNIX/Linux command line
Home Man Pages
EXT2ONLINE(8) EXT2ONLINE(8)
NAME
ext2online - online (mounted) ext2 filesystem resizer
SYNOPSIS
ext2online [-C fd] [-d] [-q] [-v] [-V] {device|mountpoint}
[size[b|K|M|G|T]]
DESCRIPTION
The ext2online tool resizes ext2 file systems while they are mounted
and in use by the system. It is OK to resize the filesystem even
while programs have open files and are writing into the filesystem.
It is only possible to enlarge a mounted filesystem. To be able to
use ext2online, you need to have the Online ext2 resize support (CON-
FIG_EXT2_RESIZE) feature enabled in the kernel (after applying the
appropriate patch for the 2.x series of kernels).
The filesystem specified by device (partition, loop device, logical
volume, ...) or mountpoint must currently be mounted, and it will be
enlarged to fill the device, by default. If the optional size parame-
ter is specified, then this size will be used instead. If the size
parameter does not have an optional modifier, it will be taken to be
in ext2 filesystem blocks (which can be 1k, 2k, or 4k - use
dumpe2fs(8) to find out more information about the current filesys-
tem). The modifiers b, K, M, G, or T mean the size parameter is given
in 512-byte blocks, kilo-, mega-, giga-, or terabytes respectively.
The ext2online program does not change the size of the actual device -
only the filesystem. If you wish to enlarge a filesystem, you must
make sure you expand the underlying device first. This can be done
online for Logical Volumes by using lvextend(8) from the LVM package,
or for ease-of-use you can use e2fsadm(8) which combines the LV exten-
sion and ext2 filesystem resizing into one step. Alternately, you may
be able to use facilities in md or RAID facilities in the hardware, if
you are not using a partition table. It is not possible to do this by
using the fdisk(8) family of tools to extend a partition while it is
mounted (at least the author has not been able to successfully do
this).
Because of the original design of the ext2 filesystem did not have
online resizing in mind, there are certain limitations to the amount
of resizing that can be done while the filesystem is mounted, if you
haven't done any preparation for the resize. The default block size
for ext2 was 1k blocks until v1.15 of e2fsprogs (1999), where it
changed to 4k blocks for filesystems larger than 512MB.
With no filesystem preparation, it is always possible to resize to the
next 256MB boundary for 1k filesystems, the next 2GB boundary for for
2k filesystems, and the next 16GB boundary for 4k filesystems.
OPTIONS
-C fd, --completion=fd
Output completion information to file descriptor fd.
-d, --debug
Turn on debugging messages.
-q, --quiet
Do not print anything but error messages.
-v, --verbose
Turn on normal verbose status messages.
-V, --version
Print the version number and exit.
RETURN VALUES
0 Resizing successful
1 Error in command line (options or specified device)
2 Error in specified size
3 Error in pre-resizing (user space) operation
4 Error during the in-kernel resizing operation
5 Error in post-resizing operation (update of metadata backups)
EXAMPLES
The following example shows how to test ext2online with a spare parti-
tion. First a filesystem of 32MB is created on the device, mounted,
and the size is verified. The filesystem is then extended to fill the
device (the default action when no size is given), and the new size is
verified.
dd if=/dev/zero of=/tmp/file bs=1k count=64k
mke2fs -f /tmp/file 32768
mkdir /mnt/test
mount -o loop,debug,check=strict /tmp/file /mnt/test
df /mnt/test
ext2online -d -v /tmp/testfile
df /mnt/test
By using the debug and check=strict options to mount, as well as the
-d and -v flags to ext2online, we will see the user-space status mes-
sages, and the kernel messages will be logged by syslog.
WARNING
Note that resizing a mounted filesystem is inherently dangerous and
may corrupt filesystems, although no errors resulting in data loss
have ever been reported to the author. In theory online resizing
should work fine with arbitrarily large filesystems, but it has not
yet been tested by the author on a filesystem larger than 11GB. Use
with caution. Backups are always a good idea, because your disk may
fail at any time, you delete files by accident, or your computer is
struck by a meteor.
AUTHOR
The ext2online program was written by Andreas Dilger using the ext2 resizing tools developed by Lennert Buyten-
hek . The ext2online kernel patches are available as
part of the GNU ext2resize package at UNIX/Linux commands referenced on this page: