Linux and File Systems What is a file system?

Linux and File Systems What is a file system? It's simply a way to represent binary data on a block device

Linux and File Systems What is a file system? It's simply a way to represent binary data on a block device What makes one file system different from another?

Linux and File Systems What is a file system? It's simply a way to represent binary data on a block device What makes one file system different from another? Journaling Extended Attributes Quota Support Access Control Lists Compression Network Support Handling of sparse files

File Permissions Three groups of flags: e.g.: rw-r--r-- First group is for the owning user R for read W for write X for execute Second group is for owning group Third group is for everyone else

Directory Permissions Three groups of flags: e.g.: rwxr-xr-x First group is for the owning user R for read files in the directory W for writing of files in the directory X for entering into the directory Second group is for owning group Third group is for everyone else

Access Control Lists Used to allow more users/groups access to a directory or file Command: setfacl -m u:rw-:<username> <file> Also allows default permissions to be set on new files created in a directory Generally requires the acl mount option

Extended Attributes Used to store additional metadata with a file For example, Samba uses user.DOS_ATTRIB to store DOS attributes inside Linux extended attributes. Generally requires the user_xattr option

Disk Quotas Used to restrict how much data can be written to a mount point by a user or group Stores its data within two files, aquota.user and aquota.group Usually requires the usrquota and grpquota mount options

Mount Points, Inodes and Links Strictly speaking, you don't mount a file system, you mount a block device that contains a file system.

Mount Points, Inodes and Links Strictly speaking, you don't mount a file system, you mount a block device that contains a file system. Inodes Inodes are like indexes within a file system that contain the raw file data and additional metadata.

Mount Points, Inodes and Links Strictly speaking, you don't mount a file system, you mount a block device that contains a file system. Inodes Inodes are like indexes within a file system that contain the raw file data and additional metadata. Links (specifically hardlinks) point directly to the file. A file can have more than one hard link which links the file at different locations in the file system hierarchy.

Mount Points, Inodes and Links Strictly speaking, you don't mount a file system, you mount a block device that contains a file system. Inodes Inodes are like indexes within a file system that contain the raw file data and additional metadata. Links (specifically hardlinks) point directly to the file. A file can have more than one hard link which links the file at different locations in the file system hierarchy. Symlinks are a special file that points to another file or directory. Unlike hardlinks, symlinks can branch across file systems and can link to directories.

Network File Systems Deal with multiple access Require all the same features as local file systems File locking can become difficult on network file systems Different levels of support: Encryption Authentication Caching

Journaling Treat a file system like a database Most file systems are now journaled Handle error recovery much better