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Look at my bizarre sda4 partition. It is just 1K in size! Be mindful that this is not cluster size, this is partition size. I did not knowingly install this sda4 super small partition. This is not my boot partition, it's some other thing. I can't seem to find anyone else with the same tiny partition.

For what reason did this small sda4 partition get created? Is it safe or malware?

This is a fresh installation of Ubuntu 12.04.02LTS for Amd64. The computer has just one physical hard disk and one DVD device at this time. This is not a multiboot computer at this time, only one OS at this time.

Here is the output from program lsblk:

ga@moonentity:~$ lsblk

sda      8:0    0 465.8G  0 disk 
├─sda1   8:1    0   300M  0 part /boot
├─sda2   8:2    0  48.8G  0 part /
├─sda3   8:3    0   5.9G  0 part [SWAP]
├─sda4   8:4    0     1K  0 part 
└─sda5   8:5    0   9.3G  0 part /home
sr0     11:0    1  1024M  0 rom
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Do you have over 400GB of unallocated space? Was that intentional? – drewbenn Apr 9 '13 at 16:47
Yes I have 400GB of unallocated space on purpose. It will be used for another OS eventually. – GeoffreyA Apr 9 '13 at 20:48
up vote 4 down vote accepted

Check the output of fdisk -l too. @eppesuig got it right, /dev/sda4 is an extended partition to contain the logical `/dev/sda5 partition

On my system:

:) ✭ [~] $> sudo lsblk 
sda      8:0    0 465.8G  0 disk 
├─sda3   8:3    0  39.1G  0 part /
├─sda4   8:4    0     1K  0 part 
├─sda5   8:5    0 422.7G  0 part /home
└─sda6   8:6    0     4G  0 part [SWAP]
sr0     11:0    1  1024M  0 rom 


:) ✭ [~] $> sudo fdisk -l

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 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
Disk identifier: 0xe3102a4b

   Device Boot      Start         End      Blocks   Id  System
/dev/sda3            2048    81919999    40958976   83  Linux
/dev/sda4        81920000   976771071   447425536    5  Extended
/dev/sda5        81922048   968302591   443190272   83  Linux
/dev/sda6       968304640   976771071     4233216   82  Linux swap / Solaris

As you can see the 1K /dev/sda4 is really a "container" for the logical partitions /dev/sda5 and /dev/sda6, fdisk shows the "real" block occupation (447425536 blocks) which is the space occupied by sda5 and sda6 (plus some more, probably partition data).

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Now it does look like sda4 (Extended) merely contains sda5. I ran fdisk -l, as you suggested. – GeoffreyA Apr 9 '13 at 21:34
I have upvoted your answer, but Stackexchange refused it. I have also accepted your answer, which Stackexchange permitted. Thanks to all for helping out! Stackexchange is a little bit derpy sometimes. – GeoffreyA Apr 9 '13 at 21:41
@user36849 yes, in your case /dev/sda4 contains only sda5. In my case sda4 is logical, too. – Mr Shunz Apr 10 '13 at 8:14

That's probably because sda5 is a logical partition and maybe its does have different rounding offset than physical ones. Or Ubuntu installer may have created sda4 on purpose this size. I think you can really ignore it safely.

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Agreed, now it does look like sda4 (Extended) merely contains sda5, and I think I can ignore it safely, as you suggested. Thank you for replying. I wish I could give more than one up vote. – GeoffreyA Apr 9 '13 at 21:33

I ran sudo fdisk -l, as suggested by Mr. Shunz. I have accepted the answer by Mr. Shunz.

(BTW, Stackexchange would not permit me to format this information clearly using the Comment feature. Carriage returns which I attempted to insert merely posted the comment prematurely. Therefore I used the Answer feature instead, so that others could read this information and understand it.)

Device Boot Start End Blocks Id System

/dev/sda1 * 2048 616447 307200 83 Linux

/dev/sda2 616448 103016447 51200000 8e Linux LVM

/dev/sda3 103016448 115304447 6144000 82 Linux swap / Solaris

/dev/sda4 115306494 134836223 9764865 5 Extended

/dev/sda5 115306496 134836223 9764864 83 Linux

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