Moving an ibd file temporarily to free up disk space
It would make more sense to me to take a backup, remove the table instead of moving it, perform your optimize and then restore the table you dropped. This would avoid moving tables around unnecessarily and leaving your database in an incoherent state. You would also want to prevent incoming connections from the outside by putting bind-address = 127.0.0.1 in my.cnf and then restarting mysql. 

Backup your whole database first with mysqldump

mysqldump 
--single-transaction \
--routines \
-u root -p nameofdatabase | gzip -9 &gt; nameofdatabase.gz


--single-transaction is the safest way to backup innodb

--routines backsup stored procedures.

gzip just compresses the backup nicely, you can open it backup with zcat. 

1: Backup the table in question

mysqldump 
--single-transaction \
-u root -p nameofdatabase nameoftable | gzip -9 &gt; nameoftable.gz


2: Make sure the backup you created of the table has your data with zcat

zcat nameoftable.gz | less


Drop the table

mysql&gt; drop table nameoftable;


3: Perform your maintenance with optimize

4: Restore the table

zcat nameoftable.gz | mysql -u root -p nameofdatabase