renew /boot
A year ago, I had fun with the set-up of
discworld. After the accident with
not so solid SDD, I started looking closer at my desktop.
I made some small configuration mistakes, and I’m going to fix all of them, one by one.
Let’s start with /boot. What’s wrong with it? I use whole disk space from USB drive to store boot loader with required files.
dirdival@discworld:~$ lsblk /dev/sdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdd 8:48 1 7,5G 0 disk
└─sdd1 8:49 1 7,5G 0 part /boot
dirdival@discworld:~$ du -sh /boot/
65M /boot/
The idea is to reduce the size of the partition and have more space for storing other data. I’m not going to work with
my key-boot disk, even if I have a backup of it. Let’s start with a new one pendrive.
The first thing is simple. Create the a new partition and set the same file system.
dirdival@discworld:~$ cat /etc/fstab | grep boot
# /boot was on /dev/sdf1 during installation
UUID=35fac341-4759-491b-8a07-e24f1768417d /boot ext2 defaults 0 2
I have the new fresh device
dirdival@discworld:~$ lsblk /dev/sdf
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdf 8:80 1 29,3G 0 disk
which is not empty:
dirdival@discworld:~$ sudo parted /dev/sdf
GNU Parted 3.2
Using /dev/sdf
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print
Model: General UDisk (scsi)
Disk /dev/sdf: 31.5GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Disk Flags:
Number Start End Size File system Flags
1 0.00B 31.5GB 31.5GB ntfs
(parted)
Get rid of the default configuration:
(parted) rm 1
(parted) mktable msdos
Warning: The existing disk label on /dev/sdf will be destroyed and all data on this disk
will be lost. Do you want to continue?
Yes/No? Yes
(parted) print
Model: General UDisk (scsi)
Disk /dev/sdf: 31.5GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
(parted)
After that, we simply create the first small partition and set the boot flag on it.
(parted) mkpart primary
File system type? [ext2]? ext2
Start? 2048s
End? 512MB
(parted) print
Model: General UDisk (scsi)
Disk /dev/sdf: 31457MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1.05MB 512MB 511MB primary ext2 lba
(parted) toggle 1 lba
(parted) toggle 1 boot
(parted) print
Model: General UDisk (scsi)
Disk /dev/sdf: 31457MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1.05MB 512MB 511MB primary ext2 boot
(parted) quit
One thing may look odd here, start value 2048s. If you are interested, follow
Ian Chard post for more details.
The second part is also obvious, we create proper file system and copy data from /boot.
dirdival@discworld:~$ sudo mkfs.ext2 /dev/sdf1
mke2fs 1.43.4 (31-Jan-2017)
Creating filesystem with 498688 1k blocks and 124928 inodes
Filesystem UUID: 51afab14-a5fc-423f-bb67-f62f614ee096
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409
Allocating group tables: done
Writing inode tables: done
Writing superblocks and filesystem accounting information:
done
dirdival@discworld:~$ sudo mount /dev/sdf1 /media/usb
dirdival@discworld:~$ cd /boot
dirdival@discworld:/boot$ sudo cp -rp ./ /media/usb/
dirdival@discworld:/boot$ sudo umount /media/usb
Is it all? Not yet. The time has come for non-clear things which are mandatory.
Even if we have all the data and we set boot flag, it doesn’t mean that it works. We need a boot loader.
dirdival@discworld:~$ sudo grub-install /dev/sdf
Installing for i386-pc platform.
Installation finished. No error reported.
dirdival@discworld:~$
And the last thing. Let’s see how current configuration for /boot looks like:
dirdival@discworld:~$ cat /etc/fstab | grep boot
# /boot was on /dev/sdf1 during installation
UUID=35fac341-4759-491b-8a07-e24f1768417d /boot ext2 defaults 0 2
It’s required the specific UUID. Our new device has a new one:
dirdival@discworld:~$ lsblk -f /dev/sdf1
NAME FSTYPE LABEL UUID MOUNTPOINT
sdf1 ext2 51afab14-a5fc-423f-bb67-f62f614ee096
Here we can do two things. We can change /etc/fstab to use the new one UUID, or we can preserve the old one.
I prefer the second solution because in case of any problem we can use the old boot-key device.
But wait, there is one more thing. We can’t have two partitions with the same UUID. This magic number is used to recognise
devices. When you have two partitions, with the same number, only one is visible. Right now we use this UUID:
dirdival@discworld:~$ lsblk /dev/sdd -f
NAME FSTYPE LABEL UUID MOUNTPOINT
sdd
└─sdd1 ext2 35fac341-4759-491b-8a07-e24f1768417d /boot
How to deal with it? We have to unmount /boot, unplug it, and set UUID for the first partition on the new device.
sudo umount /boot
dirdival@discworld:~$ lsblk /dev/sdd -f
lsblk: /dev/sdd: not a block device
Before the change /dev/sdf1 has this UUID
dirdival@discworld:~$ lsblk -f /dev/sdf1
NAME FSTYPE LABEL UUID MOUNTPOINT
sdf1 ext2 51afab14-a5fc-423f-bb67-f62f614ee096
Change, very simple:
dirdival@discworld:~$ sudo tune2fs /dev/sdf1 -U 35fac341-4759-491b-8a07-e24f1768417d
and check:
dirdival@discworld:~$ lsblk -f /dev/sdf1
NAME FSTYPE LABEL UUID MOUNTPOINT
sdf1 ext2 35fac341-4759-491b-8a07-e24f1768417d /boot
How you can see Debian even assumes that we have the boot device plugged-in.
We can make one extra change
to gain more space.
dirdival@discworld:~$ df -h /dev/sdf1
Filesystem Size Used Avail Use% Mounted on
/dev/sdf1 472M 67M 381M 15% /boot
dirdival@discworld:~$ sudo tune2fs -m 0 /dev/sdf1
dirdival@discworld:~$ df -h /dev/sdf1
Filesystem Size Used Avail Use% Mounted on
/dev/sdf1 472M 67M 406M 15% /boot
After the restart, we have the new boot-key device with plenty of free space for further use. Was it worth it? From my point of view, definitely yes.