Creating a custom database for kraken2 using NCBI and SILVA fasta files

Currently im working on a project where I need to use a metagenomic identifier. I chose to use kraken2. Im encountering some problems using kraken2 and making a custom database.

When I try to make a custom database with the following line:

kraken2-build --build --db custom_database /home/database/arb-silva.de_2024-03-06_id1308990_tax_silva_trunc.fasta

But I get the following error, no matter what I try:

Extra arguments on command line.Usage: kraken2-build [task option] [options]Task options (exactly one must be selected):  --download-taxonomy        Download NCBI taxonomic information  --download-library TYPE    Download partial library                             (TYPE = one of "archaea", "bacteria", "plasmid","viral", "human", "fungi", "plant", "protozoa","nr", "nt", "UniVec", "UniVec_Core")  --special TYPE             Download and build a special database                             (TYPE = one of "greengenes", "silva", "rdp")  --add-to-library FILE      Add FILE to library  --build                    Create DB from library                             (requires taxonomy d/l'ed and at least one file                             in library)  --clean                    Remove unneeded files from a built database  --standard                 Download and build default database  --help                     Print this message  --version                  Print version informationOptions:  --db NAME                  Kraken 2 DB name (mandatory except for                             --help/--version)  --threads #                Number of threads (def: 1)  --kmer-len NUM             K-mer length in bp/aa (build task only;                             def: 35 nt, 15 aa)  --minimizer-len NUM        Minimizer length in bp/aa (build task only;                             def: 31 nt, 12 aa)  --minimizer-spaces NUM     Number of characters in minimizer that are                             ignored in comparisons (build task only;                             def: 7 nt, 0 aa)  --protein                  Build a protein database for translated search  --no-masking               Used with --standard/--download-library/                             --add-to-library to avoid masking low-complexity                             sequences prior to building; masking requires                             dustmasker or segmasker to be installed in PATH,                             which some users might not have.  --max-db-size NUM          Maximum number of bytes for Kraken 2 hash table;                             if the estimator determines more would normally be                             needed, the reference library will be downsampled                             to fit. (Used with --build/--standard/--special)  --use-ftp                  Use FTP for downloading instead of RSYNC; used with                             --download-library/--download-taxonomy/--standard.  --skip-maps                Avoids downloading accession number to taxid maps,                             used with --download-taxonomy.  --load-factor FRAC         Proportion of the hash table to be populated                             (build task only; def: 0.7, must be                             between 0 and 1).  --fast-build               Do not require database to be deterministically                             built when using multiple threads.  This is faster,                             but does introduce variability in minimizer/LCA                             pairs.  Used with --build and --standard options.

Does anybody have any idea about this?I also tried it with a NCBI .fasta file, but still didn't work.

Thanks in advance!

Kind regards!