Steps
Before we can resize the root file system, we need the OS to detect the new size of the disk.
In this case, we use the fdisk command to show the current disk size. Which in this case is 120GB. (I know a 120GB root file system is not a good idea, but this is a lab.)
[email protected]:~# fdisk -l /dev/sda Disk /dev/sda: 120 GiB, 128849018880 bytes, 251658240 sectors Disk model: Virtual disk Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: gpt Disk identifier: DDC91865-B329-443D-AFFF-0898C341D65C Device Start End Sectors Size Type /dev/sda1 2048 4095 2048 1M BIOS boot /dev/sda2 4096 4198399 4194304 2G Linux filesystem /dev/sda3 4198400 251656191 247457792 118G Linux filesystem [email protected]:~# We now need to tell the OS to scan all the disks for changes. We do this by running a script I created called DiskScan. This script walks through all the disks and looks for changes.
curl https://raw.githubusercontent.com/mattmattox/DiskScan/master/rescan_disks.sh | bash [email protected]:~# curl https://raw.githubusercontent.com/mattmattox/DiskScan/master/rescan_disks.sh | bash % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 363 100 363 0 0 1553 0 --:--:-- --:--:-- --:--:-- 1551 Scan for new disk(s). host0 host1 host10 host11 host12 host13 host14 host15 host16 host17 host18 host19 host2 host20 host21 host22 host23 host24 host25 host26 host27 host28 host29 host3 host30 host31 host32 host4 host5 host6 host7 host8 host9 Scan for disk size change. sda [email protected]:~# We can now see that the disk size has changed. Note, we can ignore the GPT error as we’ll be fixing it as part of the next step.
[email protected]:~# fdisk -l /dev/sda GPT PMBR size mismatch (251658239 != 419430399) will be corrected by write. The backup GPT table is not on the end of the device. Disk /dev/sda: 200 GiB, 214748364800 bytes, 419430400 sectors Disk model: Virtual disk Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: gpt Disk identifier: DDC91865-B329-443D-AFFF-0898C341D65C Device Start End Sectors Size Type /dev/sda1 2048 4095 2048 1M BIOS boot /dev/sda2 4096 4198399 4194304 2G Linux filesystem /dev/sda3 4198400 251656191 247457792 118G Linux filesystem [email protected]:~# Resize the root partition
At this point, the disk has the available space we need. We can now resize the root partition.
[email protected]:~# parted /dev/sda GNU Parted 3.4 Using /dev/sda Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Warning: Not all of the space available to /dev/sda appears to be used, you can fix the GPT to use all of the space (an extra 167772160 blocks) or continue with the current setting? Fix/Ignore? Fix Model: VMware Virtual disk (scsi) Disk /dev/sda: 215GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 1049kB 2097kB 1049kB bios_grub 2 2097kB 2150MB 2147MB ext4 3 2150MB 129GB 127GB (parted) resizepart 3 -1 (parted) p Model: VMware Virtual disk (scsi) Disk /dev/sda: 215GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 1049kB 2097kB 1049kB bios_grub 2 2097kB 2150MB 2147MB ext4 3 2150MB 215GB 213GB (parted) q Information: You may need to update /etc/fstab. [email protected]:~# Note: The -1 is the size of the partition. This tell parted to use the remaining space on the disk.
Resize the file system
At this point, we have expanded the root partition to the new size. We can now resize the file system.
[email protected]:~# resize2fs /dev/sda3 resize2fs 1.46.5 (30-Dec-2021) Filesystem at /dev/sda3 is mounted on /; on-line resizing required old_desc_blocks = 2, new_desc_blocks = 13 The filesystem on /dev/sda3 is now 51428620 (4k) blocks long. Force a filesystem check on next reboot
At this point, we have expanded the file system to the new size. We can now force a filesystem check on the next reboot.
Note: This step is optional but is recommended.
How to resize ext4 root partition live without umount on Linux
This article will focus on how to resize EXT4 root partition without unmount. This is an easy way for some system where you are unable to unmount root partition and the system can be recovered easily if something goes wrong like for example AWS instance.
Resizing any live partition without unmout comes with a tremendous risk of loosing data thus it is not recommended. If you a have a sensitive data stored on your system, it is always recommended to take the system down make a backup and resize the partition while it is not mounted.
In the following example we are going to resize a partition of a fresh single partition AWS Linux instance. The current partition size is 7.8GB:
# df -h . Filesystem Size Used Avail Use% Mounted on /dev/xvda1 7.8G 642M 6.8G 9% /
However, the disk size reports 20GB:
# fdisk -l Disk /dev/xvda: 20 GiB, 21474836480 bytes, 41943040 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0xd7f2e0e8 Device Boot Start End Sectors Size Id Type /dev/xvda1 * 4096 16773119 16769024 8G 83 Linux
The above partition is mounted as root and thus the partition cannot be unmount:
# umount / umount: /: target is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1))
All what needs to be done is take a note of a starting sector of a current partition, which in our case is 4096. Remove the partition and recreate a new, larger partition starting from sector 4096. For this we are simply going to use fdisk command. Let’s start by printing again our current partition table:
# fdisk /dev/xvda Welcome to fdisk (util-linux 2.25.2). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): p Disk /dev/xvda: 20 GiB, 21474836480 bytes, 41943040 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0xd7f2e0e8 Device Boot Start End Sectors Size Id Type /dev/xvda1 * 4096 16773119 16769024 8G 83 Linux
Once again please take a note of the starting sector 4096. Still in fdisk ‘s interactive mode remove partition:
Command (m for help): d Selected partition 1 Partition 1 has been deleted.
Next, create a new partition right on the top of the previous and ensure that you use same starting sector:
Command (m for help): n Partition type p primary (0 primary, 0 extended, 4 free) e extended (container for logical partitions) Select (default p): p Partition number (1-4, default 1): First sector (2048-41943039, default 2048): 4096 Last sector, +sectors or +size (4096-41943039, default 41943039): Created a new partition 1 of type 'Linux' and of size 20 GiB.
Make the partition 1 bootable and print new partition table:
Command (m for help): a Selected partition 1 The bootable flag on partition 1 is enabled now. Command (m for help): p Disk /dev/xvda: 20 GiB, 21474836480 bytes, 41943040 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0xd7f2e0e8 Device Boot Start End Sectors Size Id Type /dev/xvda1 * 4096 41943039 41938944 20G 83 Linux
Confirm all new details and write new partition table:
Command (m for help): w The partition table has been altered. Calling ioctl() to re-read partition table. Re-reading the partition table failed.: 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).
At this point the system needs to be rebooted in order to remount our root partition with a new size. Force fsck on next reboot to ensure that the partition is checked before it is mounted. To do so just create an empty file called forcefsck in the root of your / partition:
Reboot your system. Once the system is up again check the partition size:
df -h . Filesystem Size Used Avail Use% Mounted on /dev/xvda1 20G 644M 19G 4% /
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