So too are /etc/services, /etc/crontab, /etc/phones, /etc/ttys, /etc/hosts, and /etc/protocols. The /etc/fstab file is a single table, with variable length records, non-linefeed whitespace characters as field separator, and the linefeed as record separator. So too are /etc/group, /etc/shadow, and /etc/gshadow. The Version 7 /etc/passwd file is a single table, with variable length records, the colon character as field separator, and the linefeed as record separator. The user account database on Linux is a collection of flat files. Here are some flat file databases that you encounter daily: You might think that you do not encounter such things any more, or at the very least that you do not encounter them on Unix and Linux. (For example: A could be the master file to the start of today, B could be today's transactions, and C would be the master file to date for tomorrow's run.) Everyday flat file databases 
Flat file databases used to be commonly stored on media which were good for sequential access, such as magnetic tape, and database updates would sometimes take the form of reading from input tapes A and B and merging to output tape C. Insertions and deletions involve processing the whole file. One has to read and write them linearly and sequentially, because the concept does not require records to be sorted or even to be keyed. This relates to how one accesses flat file databases. One might encounter terms such as Basic Sequential Access Method (BSAM) and Queued Sequential Access Method (QSAM) bandied about in the literature when discussing this.
The file may comprise fixed length records, with fields denoted by column positions, or variable length records, with records and fields separated from one another by delimiter characters. The structure is not relational, hierarchical, or networked. It is a database that comprises exactly one table in one file. In the context of databases, a flat file database satisfies the following: 
Dirkt is right to ask for context, but is very wrong about flat files not being databases or containing records.
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