Is it possible to enlarge the / partition without rebooting?

Question

I can enlarge the root (/) partition with fdisk without rebooting (deleting an recreating it with the same 1st sector, but greater last sector).

However, I cannot make the kernel to re-read the partition table :

# partx -va /dev/vda
partx: /dev/vda: adding partition #5 failed: Device or resource busy
partx: /dev/vda: error adding partition 5

# kpartx -va /dev/vda
device-mapper: reload ioctl on vda5 failed: Invalid argument
add map vda5 : 0 41492480 linear 0:0 2048

# hdparm -z /dev/vda
/dev/vda:
 re-reading partition table
 BLKRRPART failed: Device or resource busy

# sfdisk -R /dev/vda
BLKRRPART: Device or resource busy
This disk is currently in use.

I know what I am doing, and the ext filesystems within the partitions support online enlargement.

Is there a way forcing the kernel to update its partition table?

EDIT: I know about LVM, but it is not an answer for this question.

Solution

The kernel will use the old (cached) partition table until you unmount all partitions on the affected disk.

Since you can't unmount and mount the / partition meantime the system is running, the only option you have is a reboot.

Next time try to use LVM, because it allows you to resize volumes (even the root one) without necessitating changing of the partition table.

Comments

[taliezin]

You can try with partprobe. I don't know if it helps.

[Totor]

@taliezin I just tried, it doesn't help.

[taliezin]

Sorry, take a look at this.

[jaromrax]

I just wonder the unusual name - /dev/vda. But I never tried to enlarge ext online, every operation on partition had to always be done when unmounted. Maybe readonly mount could help you...

[roaima]

@jaromrax it's from virtualisation such as KVM/qemu

[Jannis]

doesn't the resize2fs tool already do this job?

[shubham]

Is it duplicate of this Can I resize the root partition without uninstalling and reinstalling Linux (or losing data)?

[Totor]

@shubham No, this question doesn't involve resizing partitions. It's LVM stuff.

[Rabin]

@Totor, not directly relevant, but you should consider using LVM and not disk partitions.

[Totor]

The question is about partition resizing.

[OMG-1]

I fail to see where I haven't answered the question.