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How can I increase the size of the root partition of a system at runtime?

I have a partition that is not allocated after the root partition (which is also ext4), how can I add that unallocated space to the space allocated to the root partition without having to shutdown the server?

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I hate to sound like a stick in the mud, but this entails a fair bit of risk? Why does this need to happen? Is uptime the main constraint? – DevNull Sep 30 '13 at 17:28
You can't resize a partition to the left, because that would actually be a move. – Zaz May 17 '15 at 15:16
Increasing the size of ext4 parititions online is easy. The difficult part would be shrinking (your headline is about "resizing"). For people interested by ANY manipulation on a root partition (move, shrink, change filesystem, device) at runtime should consult my answer: – vaab Feb 1 at 2:28

It is possible to do a on-line resize of a ext4 filesystem, even if it's your root partition. Use the resize2fs command.

sudo resize2fs /dev/sda1

EDIT: On-line shrinking is not allowed:

root@brunojcm-htpc:/home# resize2fs /dev/sda5 2654693
resize2fs 1.42 (29-Nov-2011)
Filesystem at /dev/sda5 is mounted on /; on-line resizing required
resize2fs: On-line shrinking not supported
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From man resize2fs: The resize2fs program does not manipulate the size of partitions. If you wish to enlarge a filesystem, you must make sure you can expand the size of the underlying partition first. This can be done using fdisk(8) by deleting the partition and recreating it with a larger size or using lvextend(8),if you're using the logical volume manager lvm(8). This question is about resizing the partition, not the filesystem. The distinction is subtle but very important. – Eliah Kagan Jun 3 '12 at 7:07
You can use fdisk to delete the root partion and then recreate it at the same starting block. fdisk will write out the change, but it won't take effect till after a reboot. after the reboot you can use the resize2fs program to send the disk to fill the partion. – Jbecwar Jun 14 '12 at 15:15
I have just resized an ext4 root partition online. Therefore I can confirm it's possible. But instead of passing /dev/sda* as parameter to resize2fs, you need to pass the logical volume name. – CDR Dec 4 '12 at 22:37
I find the first paragraph of the resize2fs manpage most interesting for the initial question: The resize2fs program will resize ext2, ext3, or ext4 file systems. It can be used to enlarge or shrink an unmounted file system located on device. If the filesystem is mounted, it can be used to expand the size of the mounted filesystem, assuming the kernel supports on-line resizing. (As of this writing, the Linux 2.6 kernel supports on-line resize for filesystems mounted using ext3 and ext4.). – mo' Dec 23 '12 at 14:33
Worked for me :) – StandDuPp Nov 28 '13 at 8:57

GUI (Ubuntu 14.04 and later): GParted v0.17 and later provide a nice GUI for this. (Older versions will refuse to resize a mounted partition).

Command line (any Ubuntu version): There are three steps to this.

Step 1. The partition must first be resized. If you're using LVM, it's easy, and you presumably know how to proceed. If you're using classic partitions, it's a bit more complicated, and may require a reboot (though you never have to boot another system or live CD).

This is how I do it: Use fdisk to first delete the partition (the idea is that the data on disk will be preserved), then carefully recreate it with a larger size at the same position.


$ sudo fdisk /dev/sda

Command (m for help): p

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     9437183     4717568   83  Linux

Command (m for help): d
Selected partition 1

Command (m for help): p

   Device Boot      Start         End      Blocks   Id  System

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
Partition number (1-4, default 1): 1
First sector (2048-10485759, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-10485759, default 10485759):
Using default value 10485759

Command (m for help): p

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048    10485759     5241856   83  Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

Again, it is critical that the new partition starts at the same block as the old. The Id should also match (83 for Linux systems). Be prepared to lose all your data at the slightest typo.

To be on the safe side, you may also restore the boot flag (which according to Wikipedia is still required on some computers) by pressing a.

See the comment section for what to do if your swap partition is in the way.

By now it should be apparent why people recommend using a live CD. ;-)

Step 2. As fdisk helpfully reminds you, you must reload the partition table before proceeding. The safest way is to simply reboot; but you can also use partprobe or kpartx (more information).

Step 3. Once the partition is resized and the partition table reloaded, it's a simple matter of running resize2fs on the file system, and you can do this even when it's mounted as the root partition.


$ sudo resize2fs /dev/sda1
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This worked perfectly for me. However I did additionally ensure that the boot flag kept is original state. – Augustus Kling Aug 10 '12 at 20:56
+1, Worked for me too, thanks :) – Reddy Sep 13 '12 at 11:30
Very useful article on the same topic: cfdisk has helped me a lot. – Frosty Z May 27 '13 at 14:53
The question asked how to do this without shutting down. You will need a program that can update the kernel entries for a partition table of a disk w/ mounted partition(s). I've read that running partprobe [<device>] should work, but I don't currently have a system where I can test it. – jbo5112 Dec 2 '13 at 18:22
@jbo5112: As fdisk says, partprobe or kpartx may work instead of a reboot; see also this question. Even if you reboot, the solution is still preferable to using a live CD when it comes to downtime, where a simple reboot can be less than 10 s for a virtual machine. It's also faster in operator time, which is why I usually use this approach myself. :) – Søren Løvborg Dec 3 '13 at 18:07

You could also just make use of GParted - as long as the partition you are resizing is not the one you booted from - else I suggest the live CD option is somewhat easier for newbies.

GParted basically does all of the steps - just based on a GUI fronted.

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I booted my system with Ubuntu 12.04 Live CD and i resized ext4 partition with GParted. Worked good for me. Anyway, before this operation I backed up all my important data. – StandDuPp May 28 '13 at 20:16
i think, gparted needs partition unmounted. but i can be wrong. – Nick Jan 27 at 18:02

Just finished resizing an ext4 root partition on a live system while the root was mount.

[root@habib i686]# resize2fs /dev/vg_habib/lv_root
resize2fs 1.42 (29-Nov-2011)
Filesystem at /dev/vg_habib/lv_root is mounted on /; on-line resizing required
old_desc_blocks = 4, new_desc_blocks = 10
Performing an on-line resize of /dev/vg_habib/lv_root to 38427648 (4k) blocks.
The filesystem on /dev/vg_habib/lv_root is now 38427648 blocks long.

[root@habib i686]# 
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As stated before: -exanding live from a root system is possible.(no difficulties, as the boot section ain't to be moved)

-shrinking a live root partition needs to be done from external boot device (boot from live system cd/usb-stick), as if theres any fault, mismatch ..whatever..your system hangs, nedds to be rebooted and will eventualy not be able to boot correctly. Any sort of "but I did it and it works" is pure luck.

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Yes, you can shrink/move/grow an online root partition without any reboots (nor livecd, nor usbkey): consult this answer. It's very well written and easy to follow, although quite long and a little risky. So if you only want to grow your ext4 partition, you can stick to the conventional working resize2fs solutions.

The general solution I've lnked will work on any type of dedicated or VPS solution for instance.

TLDR; this solution implies to pivot_root to tmpfs so you can umount safely your root partition live and fiddle with it. Once done, you'll pivot_root back on your new root partition.

This allows pretty much any manipulation on the root file system (move it, change filesystem, changing it's physical device...).

No reboot are required in the process, and this allows to bypass limitation of resize2fs not being able to shrink ext4 partitions.

I have personally used this, and it works very well on debian system also, so it should work on Ubuntu. I'm very surprised not to see this in-depth solution a little more linked to the many question in stackexchange web sites that deals with the same issue.

Note: Of course if you want to grow your partition, a simple resize2fs will be enough as stated in numerous places and in other answers here.

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I think to most people, once you've stopped all programs and services accessing the root partition, you might as well have rebooted the machine. For shrinking/moving, that's may still be faster that using a live CD, but for growing (by far the most common task, and what OP asked about), there are ways that don't involve a temporary shutdown of most of the system. – Søren Løvborg Mar 8 at 18:35
@SørenLøvborg: You can restart the core services that needs continuous production while doing the full procedure. There are many configurations where you can't put LiveCD (VPS instances, dedicated servers... ) or circumstances where you want to avoid any reboots for specific reasons. The original question's title mentions "resizing", which attracts people looking for shrinking partitions online. **No other solution allows shrinking ext4 online.**This solution is risky, complex, but the most powerful of all and it fills the shortcomings of the others. – vaab Mar 9 at 5:41

only you need bootable or live cd like hiren's bootcd

and this is link

burn it on cd and restart your computer choose cdrom to boot from it and open cd from menu choose parted magic 6.7
enter image description here

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As noted previously works fine just need to reset boot flag

run 'parted'

parted /dev/sda

verify partition number

(parted) print

reset boot flag on partition number '1' in this case

(parted) set 1 boot on
(parted) quit
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