Bash Script disk partition using fdisk command

Question

I have done new partition creation and mount the disk with manual interaction one after another, i got worked for me. But instead of doing manually i am planning to write the bash script to do all the changes for us without manual interaction.

I found the below script from internet, but i am not understand how the default option will behave using below sed command

# to create the partitions programatically (rather than manually)
# we're going to simulate the manual input to fdisk
# The sed script strips off all the comments so that we can 
# document what we're doing in-line with the actual commands
# Note that a blank line (commented as "defualt" will send a empty
# line terminated with a newline to take the fdisk default.
sed -e 's/\s*\([\+0-9a-zA-Z]*\).*/\1/' << EOF | fdisk ${TGTDEV}
  o # clear the in memory partition table
  n # new partition
  p # primary partition
  1 # partition number 1
    # default - start at beginning of disk 
  +100M # 100 MB boot parttion
  n # new partition
  p # primary partition
  2 # partion number 2
    # default, start immediately after preceding partition
    # default, extend partition to end of disk
  a # make a partition bootable
  1 # bootable partition is partition 1 -- /dev/sda1
  p # print the in-memory partition table
  w # write the partition table
  q # and we're done
EOF

sudo fdisk /dev/sdc
p
n
1
p
w
lsblk
sudo mkfs -t ext4 /dev/sdc1

But after entering option p,n,1, i wanna make default for the rest of activity then finally i need write using option w.

Can you please some one help me how to make it work

code for sfdisk

  echo ';' | sfdisk /dev/sdc
  mkfs.ext4 /dev/sdc1
  mount /dev/sdc1 /opt/app/
  uid=`blkid | grep sdc1 | sed -n 's/.*UUID=\"\([^\"]*\)\".*/\1/p'`
  echo "UUID=$uid /opt/app ext4  defaults  0  2" >> /etc/fstab

After executing sfdisk command after rebooting by REHL7 system not coming up back normal mode.

Answer 1

You can do this concept via regular fdisk this way:

fdisk /dev/sdb << EOF
p
n
1



p
w
EOF

You merely need to know how many default values are needed. You can have more, without any major consequences (cosmetic ones will occur, however)

n has a max of 4 options [number, first, last, remove_old_fstype]

so you'd add ( 4 - len(args) ) newlines, then proceed.

PS n doesn't need 1 as the default argument ( as 1 is a default argument ), but the method I described above should work