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sk8harddiefast
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PostPosted: Thu Feb 13, 2014 1:05 pm    Post subject: Is this partition necessary needed? Reply with quote

According the handbook I must create a +2MB bios partition on my HDD witch I made it, as handbook said.
Now, using xfce4, I have this partition on my desktop as hdd that cannot be mounted. In fact I created +4MB (I always give bigger space that the handbook says) and now on my desktop I have a 4.2 MB Volume witch do nothing.
Is this partition really need? Has anything on it? Why appears on my xfce4 desktop? If not, how to remove it and merge it with my / space?
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PostPosted: Thu Feb 13, 2014 1:15 pm    Post subject: Reply with quote

Do you mean /boot partition or the one for EFI?
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PostPosted: Thu Feb 13, 2014 2:04 pm    Post subject: Reply with quote

The other one for EFI. No /boot of course. I have no UEFI bios.
This:
Code:
Code Listing 4.6: Creating the BIOS boot partition

Command (m for help): n
Command action
  e   extended
  p   primary partition (1-4)
p
Partition number (1-4): 1
First sector (64-10486533532, default 64): 2048
Last sector, +sectors +size{M,K,G} (4096-10486533532, default 10486533532): +2M


I thought to install gparted to merge it. Is this safe?
Also I set /boot to ext4? Is this right or wrong?
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PostPosted: Thu Feb 13, 2014 7:47 pm    Post subject: Reply with quote

According to the docs:

Quote:
A BIOS boot partition is a very small (1 to 2 MB) partition in which bootloaders like GRUB2 can put additional data that doesn't fit in the allocated storage (a few hundred bytes in case of MBR) and cannot place elsewhere. Such partitions are not always necessary, but considering the low space consumption and the difficulties we would have with documenting the plethora of partitioning differences otherwise, it is recommended to create it in either case. For completeness, we can say that the BIOS boot partition is needed when GPT partition layout is used with GRUB2, or when the MBR partition layout is used with GRUB2 when the first partition starts earlier than the 1 MB location on the disk.


Which means that it might be needed depending on your GRUB2 configuration.
IMO merging is out of question - the question is whether this partition is required or not.
You cannot merge the contents of EFI partition into your / partition because bootloaders
need simple enough filesystem in order to be able to perform read/write and unless you
have some trivial FAT on your / root it is not the case with ext3/4, reiser, xfs, etc.

Regarding visibility: are you sure you have set 'ef' as the partition type?
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PostPosted: Thu Feb 13, 2014 7:58 pm    Post subject: Reply with quote

No. I didn't set it during installation because I was thinking that this is for uefi only. Using gparted, I deleted complete this partition. When I opened gparted this partition was with exclamation mark.
Ok. We need it. Now what I can do to fix all this? I can reverse with gparted to set again the allocated space on primary but as FAT 32? And after that? I must go to fdisk? PS. I set the grub with the most simple way that the documentation says. I remember that I just give a command and created.
I have this options and how I have partition my hdd: http://s3.postimg.org/e5hre0y0h/IMG_20140213_220549.jpg
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PostPosted: Thu Feb 13, 2014 8:37 pm    Post subject: Reply with quote

First of all you should have made backup prior to deleting anything - I mean backup of partition table, not data.

What exclamation mark do you speak about?

Gparted AFAIK after you create partition will offer you reformatting which means that it will destrony anything you had there. Don't do that
if you mean recovery. But we are not sure yet if this partition was really needed. What was on it? Any files?

In order to revert deletion you should use fdisk and input exactly the same parameters as when you were creating the partition.

All what you need is to set partition type to 'ef' and leave it as is - this will maybe waste these 4,2MB of your drive but is foolproof.
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PostPosted: Thu Feb 13, 2014 8:41 pm    Post subject: Reply with quote

Ok. Let's take everything from the beginning. I don't speak very good English and is very hard for me to understand some things.
My fdisk -l
Code:
ember@gentoo ~/Desktop $ sudo fdisk -l

Disk /dev/sda: 320.1 GB, 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
Disk identifier: 0x0006da2e

   Device Boot      Start         End      Blocks   Id  System
/dev/sda2           10240     2107391     1048576   83  Linux
/dev/sda3         2107392    10495999     4194304   82  Linux swap / Solaris
/dev/sda4        10496000   625142447   307323224   83  Linux


As you see /dev/sda1 is just gone.
Ok. I can use fdisk to recreate it as handbook says but I must go to recovery mode?
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PostPosted: Thu Feb 13, 2014 8:43 pm    Post subject: Reply with quote

I see it is gone. But data are still there, only the partition info is missing (it is just a pointer to actual data).

Please simply create new partition exactly the way you did before (same offset and size).

No need of recovery mode (what do you mean?) just make sure that you are root.
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PostPosted: Thu Feb 13, 2014 8:46 pm    Post subject: Reply with quote

OK. I Take this.
Code:
sudo fdisk /dev/sda
Password:
Welcome to fdisk (util-linux 2.22.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition type:
   p   primary (3 primary, 0 extended, 1 free)
   e   extended
Select (default e): p
Selected partition 1
First sector (2048-625142447, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-10239, default 10239): +4M
Value out of range.
Last sector, +sectors or +size{K,M,G} (2048-10239, default 10239):

Just hit enter? 10239 means that on the next sector starts /dev/sda2 witch is /boot??
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PostPosted: Thu Feb 13, 2014 8:49 pm    Post subject: Reply with quote

Yes, use the default value (10239) which means that you are creating a partition that is aligned to the next one.

Don't forget to [w]rite.
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PostPosted: Thu Feb 13, 2014 8:52 pm    Post subject: Reply with quote

OK. I made this
Code:
Using default value 10239
Partition 1 of type Linux and of size 4 MiB is set

Command (m for help): t
Partition number (1-4): 1
Hex code (type L to list codes): ef
Changed system type of partition 1 to ef (EFI (FAT-12/16/32))

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: 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)
Syncing disks.


Now what I am doing?
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PostPosted: Thu Feb 13, 2014 8:53 pm    Post subject: Reply with quote

Now set its type to 'ef' and you should be safe to reboot.
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PostPosted: Thu Feb 13, 2014 8:54 pm    Post subject: Reply with quote

I already made it.
I took this:
Code:
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: 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)
Syncing disks.

So I fixed it and just reboot and I will be ok?
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PostPosted: Thu Feb 13, 2014 8:58 pm    Post subject: Reply with quote

Since I am not sure what exactly happened when you removed partition (how it is handled by gparted)
I cannot guarantee that you have actually fully reverted the deletion. Chances are, however, that this
whole 'undeleting' procedure was not necessary as you might not need this partition in the first place ;)

You may try to run partprobe and see if /dev/sda1 becomes visible (actual device node in /dev/).
If so please try to mount it somewhere to check its contents or run filesystem check.

(for filesystem check you may need dosfstools)
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PostPosted: Thu Feb 13, 2014 9:01 pm    Post subject: Reply with quote

Update: Ihad some EFI partition and this does not seem to contain a valid filesystem
so maybe you may not bother trying to check this. You should be safe to reboot.
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PostPosted: Thu Feb 13, 2014 9:04 pm    Post subject: Reply with quote

Ok. I run
Code:
sudo partprobe

and now I see my sda1 on /dev :)
And now my fdisk -l
Code:
ember@gentoo ~/Desktop $ sudo fdisk -l

Disk /dev/sda: 320.1 GB, 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
Disk identifier: 0x0006da2e

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048       10239        4096   ef  EFI (FAT-12/16/32)
/dev/sda2           10240     2107391     1048576   83  Linux
/dev/sda3         2107392    10495999     4194304   82  Linux swap / Solaris
/dev/sda4        10496000   625142447   307323224   83  Linux

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PostPosted: Thu Feb 13, 2014 9:05 pm    Post subject: Reply with quote

Is it still visible from XFCE?
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PostPosted: Thu Feb 13, 2014 9:06 pm    Post subject: Reply with quote

As i see, no. I also presses F5 to reload my screen but isn't there :)
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PostPosted: Thu Feb 13, 2014 9:07 pm    Post subject: Reply with quote

OK, so the main problem was not having proper partition type.
The question whether you need this partition is not really solved
but I suggest to leave it. It is not visible now and makes no harm.
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PostPosted: Thu Feb 13, 2014 9:14 pm    Post subject: Reply with quote

Just when I start reading and setting all gentoo, when I start creating partitions, I show this command and I was thinking that this is for UEFI systems. So I created /dev/sda1 but never run this commands.
Code:
Command (m for help): t
Partition number (1-4): 1
Hex code (type L to list codes): ef
Changed system type of partition 1 to ef (EFI (FAT-12/16/32))

I just go to create the next partition. When I set Xserver and get into Xfce4, just I see /dev/sda1 as an umounted 4MB partition. I thought that is just not needed and I try to delete it with gparted and merge it with /dev/sda4.
Never mind. You helped me to fix it and now everything seems as it should be. + I learn that is not for uefi bios.
Thank you a lot @smerf :)
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PostPosted: Thu Feb 13, 2014 9:18 pm    Post subject: Reply with quote

I was happy to help :)

To sum up:

merging - IMO technically impossible due to fs incompatibility
removing - potentially harmful way of recovering just 4,2MB
leaving as-is marked as 'ef' - safest, foolproof
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PostPosted: Thu Feb 13, 2014 9:19 pm    Post subject: Reply with quote

I agree :D
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PostPosted: Fri Feb 14, 2014 1:39 pm    Post subject: Reply with quote

Just wondering, if you have a BIOS based PC (No UEFI), why you would want an EFI partition? I think that the only time a EFI partition it's required is just in case the hardware needs it. That leaves us with two options:


    [1] It's a UEFI based computer.
    [2] It's required by the computer to activate some kind of feature. For example, in some Eee PC netbooks you need a 40 Mb EFI partition so you can use Boot Booster.


In case 1 you need it to be the first partition on the system because of the boot process and typically you will using this partition as /boot too, as the majority of[/list] bootloaders today know how to take advantage of using UEFI.
In case 2 you should be putting it as the last partition of the system, as it's read just once in the boot process. So you take advantage of that putting the partition in the slower cylinders.

As using a partition you don't actually need: You're doing the partition table, fstab, etc..., more complex without necessity. Remember that computers are prone to errors, so, the less complex the system (without actual necessity), the less errors you should take care of in a future.
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PostPosted: Fri Feb 14, 2014 1:48 pm    Post subject: Reply with quote

Bootbooster case on my old EeePC 901 was precisely the case why I adviced him to keep it as-is - this might be needed.

In case of EeePC the location on the 'disk' does not matter as it does not have one single 'cylliner'. It is SSD ;)

Besides - UEFI or not it will be used once only.

And this will never be included in the fstab so the 'complexity' argument is IMO not really important.
Moreover - classic DOS partition table has four entries anyway. Some of them may be zero but advocating
that zero is less complex than something else is rather philosophical ;)
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PostPosted: Fri Feb 14, 2014 4:34 pm    Post subject: Reply with quote

Well, my Eee PC 1008HA has an HDD, so I was talking based on my knowledge, thanks for clarifying that :) and true with that UEFI is used once too.

What I meant with the different location was that in the first case you're kinda obligated to put it as the first partition of the disk. In the second case is not, and in the case of a HDD is convenient to put it last. Like you said in SDD it doesn't matter.

The complexity I said was in relationship to reduce the possibility of human errors in the system in the first place (Poka Yoke rox). Having a useless partition in the system, just to avoid removing it and resizing the second one, which is trivial with the correct tools and procedure, makes no good for you. It's pretty easy, and happened to me more than once, to make some mistake based on partition numbers :)
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