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VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Administrator's Guide (August 2003)

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Chapter 1
The VERITAS File System
Access Control Lists
27
Access Control Lists
An Access Control List (ACL) stores a series of entries that identify specific users or groups and their
access privileges for a directory or file. A file may have its own ACL or may share an ACL with other
files. ACLs have the advantage of specifying detailed access permissions for multiple users and groups.
Refer to the getacl (1) and setacl (1) manual pages for information on viewing and setting ACLs. For
VxFS file systems created with the Version 5 disk layout, up to 1024 ACL entries can be specified. ACLs
are also supported on cluster file systems.
Online Backup
VxFS provides online data backup using the snapshot feature. An image of a mounted file system
instantly becomes an exact read-only copy of the file system at a specific point in time. The original file
system is called the snapped file system, the copy is called the snapshot.
When changes are made to the snapped file system, the old data is copied to the snapshot. When the
snapshot is read, data that has not changed is read from the snapped file system, changed data is read from
the snapshot.
Backups require one of the following methods:
• Copying selected files from the snapshot file system (using find and cpio)
• Backing up the entire file system (using fscat)
• Initiating a full or incremental backup (using vxdump)
See “Online Backup” on page 63 for information on doing backups using the snapshot feature.
Quotas
VxFS supports quotas, which allocate per-user quotas and limit the use of two principal resources: files
and data blocks. You can assign quotas for each of these resources. Each quota consists of two limits for
each resource:
• The hard limit represents an absolute limit on data blocks or files. A user can never exceed the hard
limit under any circumstances.
• The soft limit is lower than the hard limit and can be exceeded for a limited amount of time. This
allows users to temporarily exceed limits as long as they fall under those limits before the allotted
time expires.
See
“Quota Limits” on page 72 for details on using VxFS quotas.