No alias found after makeblastdb

[BioMidge]

Hello, I want to blast a fasta file which the output of usearch after sequence merging and filtering.
I have downloaded all the nucleotide files from NCBI in FASTA format and after inzipping I ended up with a file named just nt. I used the makeblastdb command and got 22(!) .nhr .nin and .nsq files. When I run the blastn command like this, while being in the database directory:
blastn -db /home/database -query /home/COIS/19-3.fa -out outfile.txt
I get an error message saying "No alias or index file found for nucleotide database"
Any ideas on how to fix this?

[maubp]

BioMidge - It sounds like you want to run a BLAST search using the "nt" database locally? The best way to do this is with the pre-made NCBI nt database files from ftp://ftp.ncbi.nlm.nih.gov/blast/db/ - and search these forums for more details as this is a common question.

[GenoMax]

You need to provide a "basename" for the index in the -db option. In your case your -db option would be -db /home/database/nt

[AntonioRFranco]

Exactly. You only mentioned the directory where your db are kept. You need to point out the name of that db

[BioMidge]

Thanks for the replies!
Maubp: I have downloaded the nt database from that location on NCBI.
I get the no alias error message again when setting the option as
-db /home/database/nt too.
Same error also appears when using the .nsq file as db
-db ref_lib.db.22.nsq (that's one of the output files after makeblastdb).
I also tried the blastdb_aliastool:
blastdb_aliastool -db ref_lib -dbtype nucl -out database -title "nt_database"
but it is asking for a GI list argument.

[GenoMax]

If you are trying to blast against nt locally best thing is to download pre-made blast indexes from NCBI (ftp://ftp.ncbi.nlm.nih.gov/blast/db/). Get all nt* files at the link and make sure they are all in the same directory. Uncompress the files and that is all you need to do before specifying -db /path_to/nt as your database option.