Filesystems tips

• You can shrink and extend unmounted ext3 or ext4 filesystem. See How To Resize ext3 Partitions Without Losing Data HowtoForge - Linux Howtos and Tutorials
• If your partitions are highly dynamic it make sense to convert them to LVM. Otherwise to work with native partition is simpler and probably faster. 
• You can remount partition with new attributes
• You can move mount point of the partition on the fly (feature unique to Linux).

Remounting filesystem with new attributes

mount -o remount,rw /

you can also loop mount cd images

mount -t iso9660 -o loop /iso/documents.iso /mnt/cdimage

List partitions

fdisk -l 

partprobe - inform the OS of partition table changes

One of the major benefits to using Red Hat Enterprise Linux is that once the operating system is up and running, it tends to stay that way. This also holds true when it comes to reconfiguring a system; mostly. One Achilles heel for Linux, until the past couple of years, has been the fact that the Linux kernel only reads partition table information at system initialization, necessitating a reboot any time you wish to add new disk partitions to a running system.

The good news, however, is that disk re-partitioning can now also be handled 'on-the-fly' thanks to the 'partprobe' command, which is part of the 'parted' package.

Using 'partprobe' couldn't be more simple. Any time you use 'fdisk', 'parted' or any other favorite partitioning utility you may have to modify the partition table for a drive, run 'partprobe' after you exit the partitioning utility and 'partprobe' will let the kernel know about the modified partition table information. If you have several disk drives and want to specify a specific drive for 'partprobe' to scan, you can run 'partprobe <device_node>'

Of course, given a particular hardware configuration, shutting down your system to add hardware may be unavoidable, it's still nice to be given the option of not having to do so and 'partprobe' fills that niche quite nicely.

partprobe [-d] [-s] [devices...]  

DESCRIPTION

This manual page documents briefly the partprobe command.

partprobe is a program that informs the operating system kernel of partition table changes, by requesting that the operating system re-read the partition table.  

OPTIONS

This program uses short UNIX style options.

-d

Don't update the kernel.

-s

Show a summary of devices and their partitions.

-h

Show summary of options.

-v

Show version of program.

Converting ext 2 to ext3 File System

To convert an ext2  filesystem to ext3, log in as root and type the following command in a terminal:

/sbin/tune2fs -j <block_device>

where <block_device> contains the ext2 filesystem you wish to convert.

A valid block device could be one of two types of entries:

• A mapped device — A logical volume in a volume group, for example, /dev/mapper/VolGroup00-LogVol02.
• A static device — A traditional storage volume, for example, /dev/hdbX, where hdb is a storage device name and X is the partition number.

Issue the df  command to display mounted file systems.

For the remainder of this section, the sample commands use the following value for the block device:

/dev/mapper/VolGroup00-LogVol02

You must recreate the initrd image so that it will contain the ext3 kernel module. To create this, run the mkinitrd  program. For information on using the mkinitrd  command, type man mkinitrd. Also, make sure your GRUB configuration loads the initrd.

If you fail to make this change, the system still boots, but the file system is mounted as ext2 instead of ext3.

NEWS CONTENTS

Old News ;-)

linux - How can I shrink an LVM partition on CentOS - Server Fault

Growing file system is easy. Shrinking the file system is trickier and not supported by all file systems. ext3 and ext4 do support shrinking, though, but BE VERY CAREFUL WITH IT. Make absolutely sure you have good backups. Then, verify once more you have good backups.

You should first shrink the file system itself with resize2fs /dev/yourdevice newsizegoeshere.

Next you need to shrink the logical volume: lvresize -L X /path/to/your/logical_volume, where X is the new size expressed in some way. I purposely left out the syntax, see man lvresize for available options to see your preferred way to tell the new size. You can subtract from the old size or just specify the new size.

Next you need to shrink the volume group itself with vgresize, if you see that necessary. Alternatively you can just create new logical volumes inside the volume group, now that the previous step with lvresize gave you some space to breathe.

If you took the vgresize route, you finally need to adjust the partition size with fdisk by deleting the partition, and recreating it with the exactly same starting block as before and making the size smaller than before.

EDIT: It appears that with LVM2 volume group shrinking is not that trivial thing to do. You may need to delete the volume group and recreate it... oh dear. So, how about my footnote, would it work?

If you and/or software fail in any of these steps, your data goes boof. So once more: MAKE SURE YOU HAVE GOOD BACKUPS.

---

Oh, and as your copy-paste mentions VMware: could you just create a new virtual disk in VMware, copy over your stuff from your over-sized disk to the new disk, nuke the over-sized disk from the orbit and call it a day?

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Last modified: February, 05, 2017