CHATTR

Section: User Commands (1)
Updated: July 2000
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NAME

chattr - change file attributes on a Linux second extended file system

SYNOPSIS

chattr [ -RV ] [ -v version ] [ mode ] files...

DESCRIPTION

chattr changes the file attributes on a Linux second extended file system.

The format of a symbolic mode is +-=[ASacdisu].

The operator `+' causes the selected attributes to be added to the existing attributes of the files; `-' causes them to be removed; and `=' causes them to be the only attributes that the files have.

The letters `ASacdisu' select the new attributes for the files: don't update atime (A), synchronous updates (S), append only (a), compressed (c), immutable (i), no dump (d), secure deletion (s), and undeletable (u).

OPTIONS

-R: Recursively change attributes of directories and their contents. Symbolic links encountered during recursive directory traversals are ignored.
-V: Be verbose with chattr's output and print the program version.
-v version: Set the file's version/generation number.

ATTRIBUTES

When a file with the 'A' attribute set is modified, its atime record is not modified. This avoids a certain amount of disk I/O for laptop systems.

A file with the `a' attribute set can only be open in append mode for writing. Only the superuser can set or clear this attribute.

A file with the `c' attribute set is automatically compressed on the disk by the kernel. A read from this file returns uncompressed data. A write to this file compresses data before storing them on the disk.

A file with the `d' attribute set is not candidate for backup when the dump(8) program is run.

A file with the `i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be written to the file. Only the superuser can set or clear this attribute.

When a file with the `s' attribute set is deleted, its blocks are zeroed and written back to the disk.

When a file with the `S' attribute set is modified, the changes are written synchronously on the disk; this is equivalent to the `sync' mount option applied to a subset of the files.

When a file with the `u' attribute set is deleted, its contents are saved. This allows the user to ask for its undeletion.

AUTHOR

chattr was written by Remy Card <Remy.Card@linux.org>.

BUGS AND LIMITATIONS

As of Linux 2.2, the `c', 's', and `u' attribute are not honored by the kernel code.

These attributes will be implemented in a future ext2 fs version.

AVAILABILITY

chattr is part of the e2fsprogs package and is available for anonymous ftp from tsx-11.mit.edu in /pub/linux/packages/ext2fs.

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