Chattr Command or Change Attributes of File

May 5, 2013 | By
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Attributes of file or extend attributes of file are simple and easy to use.  Chattr command uses to change file attributes on a Linux in ext2 or ext3 file system.  After changing attributes no one can modify or delete a file even they have full access. Chattr keep safe from accidentally deleting files or directories.

Check File Attributes

We can check what attributes are set of a file as below:

# lsattr

example:

# lsattr test.txt
- - - - - - - - - test.txt

Change Attributes of File

chattr command which changes the file attributes on a Linux, Let suppose if we will change a file attribute to '+i' attribute. 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, even root user can't modify this.

# chattr +i test.txt

# lsattr test.txt
- - - - i - - - - test.txt

If you want to changes in file you need to revert back attributes as below:

# chattr -i test.txt

if you want to allow everybody to just append data to a file and not change already entered data, you can set the append bit as follows:

# chattr +a

example

# lsattr +a test.txt
- - - - a - - - - test.txt

revert back as:

# chattr -a test.txt

There are more options that can use with chattr command

Options

-R Modify directories and their contents recursively.

-V Print modes of attributes after changing them.

-v version Set the file's version.

Opcodes

+ Add attribute.

- Remove attribute.

= Assign attributes (removing unspecified attributes).

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.

Attributes

A Don't update access time on modify.

a Append only for writing. Can be set or cleared only by a privileged user.

c Compressed.

d No dump.

i Immutable. Can be set or cleared only by a privileged user.

j Journalled file. This is useful only in cases where you are using an ext3 filesystem mounted with the data="ordered" or data="writeback" attributes. The data="journalled" option for the filesystem causes this operation to be performed for all files in the system and makes this option irrelevant.

S Synchronous updates.

s Secure deletion. The contents are zeroed on deletion, and the file cannot be undeleted or recovered in any way.

u Undeletable. This causes a file to be saved even after it has been deleted, so that a user can undelete it later.

Filed Under : FILE SYSTEM, HOWTOS, LINUX COMMANDS

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