C.0 POSIX File System Support

This section provides information regarding the TSAFS support of POSIX-compliant file systems like BtrFS, ReiserFS, Ext2, Ext3, and XFS file systems on Open Enterprise Server (OES). These file systems are sometimes referred to in the document as non-NSS file systems.

POSIX-compliant means file systems that comply to the IEEE Std 1003.1 system interfaces. For more information, See Open Group Publications Web site.

Backup of Linux POSIX file systems requires that ACLS and POSIX permissions be set on the Linux path for the LUM-enabled user performing the backup. The root user has all permissions needed to perform backup of any Linux path. You can use the Linux chmod(8) and chown(8) commands to give the backup user the Linux POSIX permissions to the directory being backed up.

The following table lists metadata that is backed up or restored to non-NSS file systems on OES 2018 or later. The table uses the definition of metadata structure fields from the definition of the structure stat. (See man page stat(2) for more information)




Mode of the file, including File types and File access permissions


Number of hard links to the file


User ID of the file


Group ID of the file


Size of the file


Time of last access


Time of last data modification

File Types

  • Block special files

  • Character special files

  • Regular files

  • Directories

  • Symbolic links

  • Socket files

Additionally, TSAFS also backs up the following information for a file or directory (when applicable),

  • Symbolic link information

  • Data stream

  • Extended ACLs (POSIX Draft ACLs)

  • Extended attribute streams

  • File attributes on a Linux second extended file system

For more information on extended ACLs, see POSIX Access Control Lists on Linux.

For more information on file attributes on a Linux second extended file system, see man page chattr(1), installed by the RPM e2fsprogs.

POSIX Compliant File Systems Limitations

  • Backing up and restoring Extended Attributes is supported within the same file system, but restoration is not supported across different file systems.

  • During restoration, a non-root user cannot overwrite the read-only files to the POSIX-complaint file systems, because write access is required for updating the files.