104.1. Create partitions and filesystems
Weight: 2
Description: Candidates should be able to configure disk partitions and then create filesystems on media such as hard disks. This includes the handling of swap partitions.
Objective
- Use various mkfs commands to set up partitions and create various filesystems such as:
- ext2/ext3/ext4
- xfs
- reiserfs v3
- vfat
- fdisk
- mkfs
- mkswap
Blocked devices
Is a technical term for any storage device which can be formatted to fixed sized blocks and blocks should be able to be accessed individually. That is Hard disks, USB Memories, CDs, ..
In long ls format, the first b indicates Block Device:
$ ls -l /dev/loop1 /dev/sd[a-z]
brw-rw---- 1 root disk 7, 1 Jan 8 10:46 /dev/loop1
brw-rw---- 1 root disk 8, 0 Jan 8 10:46 /dev/sda
Some block devices mostly used as one single filesystem (like CDs & Floppies) and some are divided into Partitions (Hard disks).
fdisk
fdisk is the main command for viewing / changing and creating partitions. -l switch is for show:
root@funlife:~# fdisk -l /dev/sda
Disk /dev/sda: 298.1 GiB, 320072933376 bytes, 625142448 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: 0x000beca1
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 43094015 43091968 20.6G 83 Linux
/dev/sda2 43094016 92078390 48984375 23.4G 83 Linux
/dev/sda3 92080126 625141759 533061634 254.2G 5 Extended
/dev/sda5 92080128 107702271 15622144 7.5G 82 Linux swap / Solaris
/dev/sda6 107704320 625141759 517437440 246.8G 83 Linux
- The Boot flag shows which partition starts the boot on DOS PCs and has no importance on LILO & GRUB
- Start and End shows the where this partition is located on the disk
- Size is size!
- ID indicated the partition format (82 is swap, 83 is linux data, ..)
It is also possible to run fdisk in interactive mode. m will show you the help:
root@funlife:~# fdisk /dev/sda
Welcome to fdisk (util-linux 2.25.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): m
Help:
DOS (MBR)
a toggle a bootable flag
b edit nested BSD disklabel
c toggle the dos compatibility flag
Generic
d delete a partition
l list known partition types
n add a new partition
p print the partition table
t change a partition type
v verify the partition table
Misc
m print this menu
u change display/entry units
x extra functionality (experts only)
Save & Exit
w write table to disk and exit
q quit without saving changes
Create a new label
g create a new empty GPT partition table
G create a new empty SGI (IRIX) partition table
o create a new empty DOS partition table
s create a new empty Sun partition table
p displays the current partitions:
Command (m for help): p
Disk /dev/sda: 298.1 GiB, 320072933376 bytes, 625142448 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: 0x000beca1
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 43094015 43091968 20.6G 83 Linux
/dev/sda2 43094016 92078390 48984375 23.4G 83 Linux
/dev/sda3 92080126 625141759 533061634 254.2G 5 Extended
/dev/sda5 92080128 107702271 15622144 7.5G 82 Linux swap / Solaris
/dev/sda6 107704320 625141759 517437440 246.8G 83 Linux
You may remember the disk layouts from other chapters. fdisk can create them. Lets first delete my first partition:
Command (m for help): p
Disk /dev/sda: 298.1 GiB, 320072933376 bytes, 625142448 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: 0x000beca1
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 43094015 43091968 20.6G 83 Linux
/dev/sda2 43094016 92078390 48984375 23.4G 83 Linux
/dev/sda3 92080126 625141759 533061634 254.2G 5 Extended
/dev/sda5 92080128 107702271 15622144 7.5G 82 Linux swap / Solaris
/dev/sda6 107704320 625141759 517437440 246.8G 83 Linux
Command (m for help): d
Partition number (1-3,5,6, default 6): 1
Partition 1 has been deleted.
I'm brave! Now lets create a smaller one there:
Command (m for help): n
Partition type
p primary (1 primary, 1 extended, 2 free)
l logical (numbered from 5)
Select (default p): p
Partition number (1,4, default 1): 1
First sector (2048-625142447, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-43094015, default 43094015): +15G
Created a new partition 1 of type 'Linux' and of size 15 GiB.
Command (m for help): p
Disk /dev/sda: 298.1 GiB, 320072933376 bytes, 625142448 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: 0x000beca1
Device Boot Start End Sectors Size Id Type
/dev/sda1 2048 31459327 31457280 15G 83 Linux
/dev/sda2 43094016 92078390 48984375 23.4G 83 Linux
/dev/sda3 92080126 625141759 533061634 254.2G 5 Extended
/dev/sda5 92080128 107702271 15622144 7.5G 82 Linux swap / Solaris
/dev/sda6 107704320 625141759 517437440 246.8G 83 Linux
This new partitioned is not formatted but still marked 83 for later use. If I needed to use this partition as swap I had to set its ID to 82:
Command (m for help): p
Disk /dev/sda: 298.1 GiB, 320072933376 bytes, 625142448 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: 0x000beca1
Device Boot Start End Sectors Size Id Type
/dev/sda1 2048 31459327 31457280 15G 83 Linux
/dev/sda2 43094016 92078390 48984375 23.4G 83 Linux
/dev/sda3 92080126 625141759 533061634 254.2G 5 Extended
/dev/sda5 92080128 107702271 15622144 7.5G 82 Linux swap / Solaris
/dev/sda6 107704320 625141759 517437440 246.8G 83 Linux
Command (m for help): t
Partition number (1-3,5,6, default 6): 1
Hex code (type L to list all codes): L
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris
1 FAT12 27 Hidden NTFS Win 82 Linux swap / So c1 DRDOS/sec (FAT-
2 XENIX root 39 Plan 9 83 Linux c4 DRDOS/sec (FAT-
3 XENIX usr 3c PartitionMagic 84 OS/2 hidden C: c6 DRDOS/sec (FAT-
4 FAT16 <32M 40 Venix 80286 85 Linux extended c7 Syrinx
5 Extended 41 PPC PReP Boot 86 NTFS volume set da Non-FS data
6 FAT16 42 SFS 87 NTFS volume set db CP/M / CTOS / .
7 HPFS/NTFS/exFAT 4d QNX4.x 88 Linux plaintext de Dell Utility
8 AIX 4e QNX4.x 2nd part 8e Linux LVM df BootIt
9 AIX bootable 4f QNX4.x 3rd part 93 Amoeba e1 DOS access
a OS/2 Boot Manag 50 OnTrack DM 94 Amoeba BBT e3 DOS R/O
b W95 FAT32 51 OnTrack DM6 Aux 9f BSD/OS e4 SpeedStor
c W95 FAT32 (LBA) 52 CP/M a0 IBM Thinkpad hi eb BeOS fs
e W95 FAT16 (LBA) 53 OnTrack DM6 Aux a5 FreeBSD ee GPT
f W95 Ext'd (LBA) 54 OnTrackDM6 a6 OpenBSD ef EFI (FAT-12/16/
10 OPUS 55 EZ-Drive a7 NeXTSTEP f0 Linux/PA-RISC b
11 Hidden FAT12 56 Golden Bow a8 Darwin UFS f1 SpeedStor
12 Compaq diagnost 5c Priam Edisk a9 NetBSD f4 SpeedStor
14 Hidden FAT16 <3 61 SpeedStor ab Darwin boot f2 DOS secondary
16 Hidden FAT16 63 GNU HURD or Sys af HFS / HFS+ fb VMware VMFS
17 Hidden HPFS/NTF 64 Novell Netware b7 BSDI fs fc VMware VMKCORE
18 AST SmartSleep 65 Novell Netware b8 BSDI swap fd Linux raid auto
1b Hidden W95 FAT3 70 DiskSecure Mult bb Boot Wizard hid fe LANstep
1c Hidden W95 FAT3 75 PC/IX be Solaris boot ff BBT
1e Hidden W95 FAT1 80 Old Minix
Hex code (type L to list all codes): 82
Changed type of partition 'Linux' to 'Linux swap / Solaris'.
Command (m for help): p
Disk /dev/sda: 298.1 GiB, 320072933376 bytes, 625142448 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: 0x000beca1
Device Boot Start End Sectors Size Id Type
/dev/sda1 2048 31459327 31457280 15G 82 Linux swap / Solaris
/dev/sda2 43094016 92078390 48984375 23.4G 83 Linux
/dev/sda3 92080126 625141759 533061634 254.2G 5 Extended
/dev/sda5 92080128 107702271 15622144 7.5G 82 Linux swap / Solaris
/dev/sda6 107704320 625141759 517437440 246.8G 83 Linux
b is code for FAT32 (windows 95).
But all we done was in memory! We need to write it to the partition table. 'v' will verify the setup:
Command (m for help): v
Remaining 11639159 unallocated 512-byte sectors.
It tells me that I have unallocated space! I'm waisting my hard but I'm fine with it. So lets save it with w command (for write):
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).
Formatting the partition
Linux can handle more than 100 kind of partitions but most commons are:
| Format | Description |
|---|---|
| ext2 | second extended filesystem was developed to address shortcomings in the Minix filesystem used in early versions of Linux. It has been used extensively on Linux for many years. There is no journaling in ext2, and it has largely been replaced by ext3 and more recently ext4. |
| ext3 | ext2 + journaling, total storage can be 1EXAByte and each file can be 16TB, ... |
| ReiserFS | ReiserFS is a B-tree-based filesystem, great for large numbers of small files, journaling, no longer in active development & does not support SELinux, replaced with Reiser4. |
| XFS | journaling, caches to RAM, great for uninterruptible power supplies |
| swap | Swap space must be formatted for use as swap space, but it is not generally considered a filesystem. |
| vfat | FAT32, no journaling, good for data exchange with windows, does not understand permissions and symbolic links |
| ext4 | newer than ext3 |
You can format your partitions with mkfs command (and mkswap for swap). This is a front end to commands like mkfs.ext3 for ext3, mkfs.ext4 for ext4 and mkfs.reiserfs for ReiserFS. full list of installed on your system is here:
root@funlife:~# ls /sbin/mk*
/sbin/mkdosfs /sbin/mkfs /sbin/mkfs.cramfs /sbin/mkfs.ext3 /sbin/mkfs.ext4dev /sbin/mkfs.minix /sbin/mkfs.ntfs /sbin/mkhomedir_helper /sbin/mkswap
/sbin/mke2fs /sbin/mkfs.bfs /sbin/mkfs.ext2 /sbin/mkfs.ext4 /sbin/mkfs.fat /sbin/mkfs.msdos /sbin/mkfs.vfat /sbin/mkntfs
The main switch is -type (or -t) to specify the format:
root@funlife:~# mkfs -t ext3 /dev/sda1
mke2fs 1.42.10 (18-May-2014)
/dev/sda1 contains a ext4 file system
last mounted on /mnt on Mon Dec 22 12:04:22 2014
Proceed anyway? (y,n) y
Creating filesystem with 5386496 4k blocks and 1349040 inodes
Filesystem UUID: 0b5aad86-b507-41b9-a0ff-cf899cb92785
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
root@funlife:~#
This will have a same effect:
mkfs.ext3 /dev/sda1
If you need to assign a lable to the partition, you have to use the -L lable_name option. Please note that in renect system, people use UUIDs instead of labels. UUID of a disk can be viewed with:
$ blkid /dev/sda1
/dev/sda1: UUID="59d8cbdb-0e78-4605-8aaf-cf02fcb85d2e" SEC_TYPE="ext2" TYPE="ext3"
GPT
Some systems use GUID Partition Table (GPT) instead of older MBR. In this case you have to use the gdisk tool which has more capabilities than fdisk.
root@funlife:~# gdisk /dev/sda
GPT fdisk (gdisk) version 0.8.8
Partition table scan:
MBR: MBR only
BSD: not present
APM: not present
GPT: not present
***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format
in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by
typing 'q' if you don't want to convert your MBR partitions
to GPT format!
***************************************************************
creating different partitions
| Partition | Format type | Sample Command | Notes |
|---|---|---|---|
| /dev/sda3 | ext4 | mkfs -t ext4 -L data/dev/sda3 |
Named it dafa. Or use the mkfs.ext4 command |
| /dev/sdb2 | xfs | mkfs -t xfs -i size=512 /dev/sdb2 |
telling it to have larger inodes (normal is 256) |
| /dev/sda8 | ReiserFS | mkfs -t reiserfs /dev/sda8 |
Or you can use mkreiserfs command. |
| /dev/sdc | FAT32 | mkfs -t vfat /dev/sdc |
Or you can use mkfs.vfat command |
| /dev/sda2 | swap | mkswap /dev/sda2 |
will be used as swap space |
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