Using variables inside a recipe

Chef Infra (archive)
1

Hi all,
I am new to Chef and I can't find a solution to the issue at hand; please read the following code:

bash 'blk-nofs' do
  user 'root'
  code <<-EOH
  for block in $(lsblk -o NAME -dn)
  do
    validation=$(blkid /dev/$"{block}")
    if [[ -z "${validation}" ]]
    then
      db_disk="${block}"
    else
    :
    fi
  done
  EOH
end

lvm_physical_volume '/dev/"${db_disk}"'

But the value of db_disk does not get exported to be used by another resource.
Is there a way to do so?
Thank you for your time.
Giuseppe

2

By default, Chef has no way of knowing that you've set a Bash variable - which will go away once its subprocess has finished.

What you'll want to do instead is to capture the script's output to a ruby variable, using Chef::Mixin::ShellOut. There's some examples here:

Once you have your value in a ruby variable, you can call it as part of a resource block.

So it might look something like this:

db_disk = ''
ruby_block "get_db_disk" do
    block do
    Chef::Resource::RubyBlock.send(:include,Chef::Mixin::ShellOut)
    db_disk = shell_out("your code here")
    end
end

lvm_physical_volume '/dev/'+db_disk do
    # pv allocation here
end
3

Hi Pahanda,
Thank you for your reply.
This is now:

db_disk = ''
ruby_block "get_db_disk" do
    block do
    Chef::Resource::RubyBlock.send(:include,Chef::Mixin::ShellOut)
    db_disk = shell_out(
"for block in $(lsblk -o NAME -dn)
do
validation=$(sudo blkid /dev/$block)
if [[ -z $validation ]]
then
db_disk=$block
else
:
fi
done"
)
    end
end

lvm_physical_volume '/dev/'+db_disk

But I get this error on run because the passed variable's value is empty:

[2019-07-05T19:23:08+00:00] FATAL: LVM::External::ExternalFailure: lvm_physical_volume[/dev/] (postgres::psql-11-dbfiles line 43) had an error: LVM::External::ExternalFailure: Fatal error,/sbin/lvm pvcreate /dev/ returned 5 with 'Device /dev/ not found (or ignored by filtering).'

Thank you again for your help.

4

That tells me that the output from the bash script didn't actually get stored to the variable, so it was empty - leaving the argument to lvm_physical_volume invalid.

I'd recommend putting some debugging in; I don't know how well the shell_out command handles line breaks like that (you might need semicolons in your bash if/else block).

6

I have also changed as follow:

db_disk = ''
ruby_block "get_db_disk" do
    block do
    Chef::Resource::RubyBlock.send(:include,Chef::Mixin::ShellOut)
    db_disk = shell_out("for block in $(lsblk -o NAME -dn); do validation=$(sudo blkid /dev/$block); if [[ -z $validation ]]; then echo $block; fi; done")
    end
end

lvm_physical_volume '/dev/'+db_disk

and I have tested the command included inside the shell_out block but it still fails to pass the value of the variable outside the block.

Can anyone help please?
Thank you

7

UPDATE:

db_disk = ''
ruby_block "get_db_disk" do
    block do
    Chef::Resource::RubyBlock.send(:include,Chef::Mixin::ShellOut)
    db_disk = shell_out!("for block in $(lsblk -o NAME -dn); do if [ -z $(sudo blkid /dev/$block) ]; then echo $block; fi; done").stdout
    puts " disk is #{db_disk}"
    puts $?.success?
    end
end

I get the disk fine:

     * ruby_block[get_db_disk] action run disk is sdb
   true
   
       - execute the ruby block get_db_disk

But still:

[2019-07-08T12:08:09+00:00] FATAL: LVM::External::ExternalFailure: lvm_physical_volume[/dev/] (postgres::psql-11-dbfiles line 18) had an error: LVM::External::ExternalFailure: Fatal error,/sbin/lvm pvcreate /dev/ returned 5 with 'Device /dev/ not found (or ignored by filtering).'

8

This can now be closed please.