EXT2ONLINE(8)                                                    EXT2ONLINE(8)


       ext2online - online (mounted) ext2 filesystem resizer


       ext2online   [-C   fd]   [-d]   [-q]   [-v]   [-V]  {device|mountpoint}


       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 filesystem).  The  modi-
       fiers  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

       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.


       -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.


       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)


       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

            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 messages,
       and the kernel messages will be logged by syslog.


       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 cau-
       tion.  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


       The ext2online program was written  by  Andreas  Dilger  <adilger@clus-
       terfs.com> using the ext2 resizing tools developed by Lennert Buytenhek
       <buytenh@gnu.org>.  The ext2online kernel patches are available as part
       of     the     GNU     ext2resize     package     at    <http://source-


       There is a limit imposed on a single filesystem resize due to the  fact
       that  ext2online  does  not  use  triple-indirect blocks for the resize
       inode.  This should not affect most users of ext2online, as  the  limit
       is  about  60GB  larger  than  the current filesystem size for 1k block


       ext2online is (C) Copyright 1999, 2000, 2001 by Andreas Dilger and  may
       be distributed under the terms of the GNU General Public License.


       dumpe2fs(8) e2fsck(8) lvextend(8)

ext2online v1.1.18                 July 2002                     EXT2ONLINE(8)

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