lk/system/partitions.md

title	tags
partitions	Documentation system

FDisk Basics

sudo fdisk /dev/sda

• m for help.

• n to make a partition.

• t to mark the partition type (see IDs below).

• w to write the changes to the disk.

Note the asterisk marking the boot partition.

IDs

ID	Meaning
83	Linux
5	Extended
82	Swap

fdisk will not help with a GPT formatted drive. For this, use gdisk, which is mostly the same.

Now that we have a partition, we can make it into a filesystem. Most will use:

sudo mkfs -t ext4 /dev/sdc1

or if you're making a swap partition, you can use:

sudo mkswap /dev/sdb2

or for the reiser filesystem, we can use:

sudo mkreiserfs /dev/sdc2

File System Types

Type	Advantages	Disadvantages
ext2		No journaling means that the file offers no crash recovery.
ext3	Journaling
ext4	Journaling and handles files of up to 16TB.
reiserfs	Journalin and stable.
btrfs	Reliable and stable
XFS	Journaling, great for large files.
VFAT	Comptable with Windows, like FAT32

Parted

sudo parted /dev/sdb

Monitoring

Look at physical and virtual partitions:

df -h

or divide things by inode - the thing which records where files are?

df -i

Examine a filesystem with:

sudo dumpe2fs /dev/sda1 | less

Prevention

There are multiple programs which work mostly the same way.

sudo tune2fs -c 30 /dev/sda1

This will check sda1 every 30 boots. It can also be checked every month.

sudo tune2fs -i 1m /dev/sda1

This thing can also make a new label for the system:

sudo tune2fs -L new_name /dev/sdb3

Repair

Start by unmounting the filesystem.

sudo umount /dev/sdc1

Then it's time to check.

sudo fsck /dev/sdc1

And possibly repair damage:

e2fsck -p /dev/sdc1

or the same with:

sudo debugfs /dev/sdc1

Mounting

You can mount with a specified filetype with:

sudo mount -t ext3 /dev/sdc2 /mnt/stick

or if you don't know the type, just try the lot:

sudo mount -a /dev/sdc1 /mnt/stick

File Systems

xfs and zfs can only be expanded.

Shrink Filesystem

NB: When I followed these instructions, the process destroyed my data. Seemed fine on the YouTube video.

Check the filesystem's health:

sudo e2fsck -f /dev/sdb1

Resize the file system to something smaller than what you want, so here I want 500G and so I resize to 450 G.

resize2fs /dev/sdb1 450G

Then delete the partition with either gdisk or fdisk, depending upon the layout.

sudo fdisk /dev/sdb

d

Then make a new filesystem of the desired type with:

n

And finally resize to the full size you want:

sudo resize2fs /dev/sdb1

And then check your disk again with e2fsck.

(The e2fsck saved my disk in the end, YMMV)

Logical Volume

Let's start with names. PV = 'Physical Volume', VG = 'Volume Group', and LV = 'Logical Volume'.

Now we can create a volume group out of sdb2 and sdc3:

sudo vgcreate my-new-vg /dev/sdb2 /dev/sdc3

Then make a new logical volume out of the volume group:

sudo lvcreate -n my-new-lv my-new-vg

Then have a look at all logical volumes:

sudo lvscan