26.8. Editing EXT File Attributes

Several UNIX filesystem types support special attributes on files beyond those that can be set with the normal chmod and chown commands. On Linux ext2 and ext3 filesystems, each file has several special options that are normally set with the chattr command. Assuming your system has at least one filesystem of this type, you can change the EXT attributes for files that it contains by following these steps:

1.
Select the file that you want to modify in the right-hand pane, and click the EXT button on the toolbar. This will bring up a window showing attributes that are currently set, assuming that the file is on an ext2 or ext3 filesystem.

2.
To stop the file's last access time being updated very time it is read, turn on the Do not update access times option. This can prevent a lot of useless disk writes on files that are read frequently.

3.
To stop processes modifying the contents of a file, check the Can only append to file option. This is useful for logfiles that you want to save from truncation or overwriting.

4.
To have the kernel automatically and transparently compress the contents of a file, turn on the Compress data on disk option. This will only have an effect if your kernel supports transparent file compression.

5.
To stop a file being read by the dump backup command (explained in Chapter 14), turn on the Do not backup with dump option.

6.
To prevent a file from being modified or deleted, check the Do not allow modification option.

7.
To have the kernel overwrite the disk blocks containing the file when it is deleted, turn on the Zero blocks when deleting attribute.

8.
To force any writes to the file to be written to disk immediately, turn on the Always sync after writing option. Normally, the kernel buffers data for writing to disk when it is most convenient.

9.
To have the kernel save the contents of the file when it is deleted, turn on the Save contents for undeletion option.

10.
Finally, click the Save button to have your changes applied to the file.

Because all the preceding attributes can be changed at the shell prompt using the chattr command, making a file unchangeable or setting it to append-only mode does not provide any protection against someone who has root access to your system.

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