--- title: "File Systems: Names, Blocks and Metadata" description: "In an inode-based, block-backed file system, directories map names to records. Records hold metadata and information locating file bytes. Paths follow these mappings; hard links share a record. Removi" canonical: https://lightmysky.com/learn/computing/file-systems-names-blocks-and-metadata-mt_jN4u3idvF3 source: https://lightmysky.com/learn/computing/file-systems-names-blocks-and-metadata-mt_jN4u3idvF3.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # File Systems: Names, Blocks and Metadata In an inode-based, block-backed file system, directories map names to records. Records hold metadata and information locating file bytes. Paths follow these mappings; hard links share a record. Removing a name differs from copying bytes or immediately reclaiming storage. Subject: Computing · Area: Computer Systems · Ages 20 to 21 Page: https://lightmysky.com/learn/computing/file-systems-names-blocks-and-metadata-mt_jN4u3idvF3 ## Ready when they can - Resolve absolute and relative paths and follow directory entries through records to data blocks - Explain hard links as names sharing one record and predict the result of removing one name - Explain why unlinking avoids overwriting file contents without guaranteeing instant deletion or reclamation ## Lesson: Names point at records, records point at blocks An absolute path starts at a file-system root. A relative path starts at the process's current working directory. In our inode-based model, each directory maps a component name to a record. Intermediate components lead through directories. If the working directory is /home/ana, notes/draft.txt resolves to /home/ana/notes/draft.txt. Paging tracks page residency in RAM frames. Here we use a block-backed, inode-based file-system model. Storage blocks are not RAM frames. A directory entry maps a name to a record; it does not contain the named file's contents. A file record holds metadata such as owner, type, permissions and size, plus information locating data blocks. Follow the name to the record, then its block information to find the stored bytes. For a regular file, ls -l may show -rw-r--r--. The leading dash marks a regular file. The next nine positions are owner, group and other fields, each with read, write and execute slots. A dash means absent. chmod 600 myfile.txt sets rw-------: owner read/write, group and other none. These mode bits do not describe every possible access or action. Hard-link names for a regular file refer to the same record on the same file system. Neither name is a special original. Both reach the same contents and metadata. Adding a hard link adds a directory entry, not an independent copied file. This discussion does not concern symbolic links or links to directories. Unlinking removes a directory entry and reduces the link count without overwriting every content block. It can be quick, but storage reclamation may need more metadata work. An ordinary byte-by-byte copy reads source bytes and writes destination contents associated with a distinct file record. Some file systems let distinct copies share physical blocks until changes require separation. *(drawing: The directory entry identifies a record. That record supplies information locating the data blocks.)* Removing one hard-link name leaves other names for the same file usable. After the last name is removed, an open file handle can still keep the file usable. In this model, space becomes reclaimable when no hard links or open handles remain. Reclamation need not be instant. Unlinking is not secure erasure; old bytes may remain until storage is reused. **Recap.** Directories map names to records; records locate data blocks. Hard links share a record. Unlinking removes a name without overwriting every content block. *Lesson, worked questions and flashcards about paths, records, permissions and hard links were written for this dataset.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Paging, Page Faults and Replacement Policies](https://lightmysky.com/learn/computing/paging-page-faults-and-replacement-policies-mt_nEEuGL89Ze) ## Optional connections - [Reading and Writing Files, Including CSV](https://lightmysky.com/learn/computing/reading-and-writing-files-including-csv-mt_j5qb4FdkdI) ## Opens up - [Crash Consistency and the Journal](https://lightmysky.com/learn/computing/crash-consistency-and-the-journal-mt_I9DT0TUmiu)