Page 164 - DCAP106_OPERATING_SYSTEM_TOOLS

Unit 9: The File System

Notes
Example:

$ ls -l bar
-rw-r--r-- 1 swift users 0 May 13 20:41 bar
$ chgrp dialout bar
$ ls -l bar
-rw-r--r-- 1 swift dialout 0 May 13 20:41 bar
If you want to change the owner and group, a single chown command can be used. That is, just
separate the target owner and group with a colon.

Example:

# chown jack:dialout template.txt

9.2.8 Attributes

Some file systems provides permission to add more attributes to files. These attributes might
have impact on the permissions/usage of these files, or on how the operating system works with
these files. Not many distributions use these attributes, because not all file systems support them.

Listing and Modifying Attributes

In order to view the attributes of a file, the lsattr command (list attributes) is used; to modify the
attributes, chattr (change attributes) command is used. Now let us create an example file:

# touch /tmp/foo
# chattr +asS /tmp/foo
Now let’s see what lsattr has to say:

# lsattr /tmp/foo
s-S--a--------- /tmp/foo
Not a big surprise, given the chattr command before. But what does it mean? Well, man
chattr gives us the information we need, but here is it in short-hand:
z z s: when the file is deleted, its blocks are zeroed and written back to disk (unlike regular files
where only the reference to the file is deleted).
z z S: when changes are made to the file, the changes are immediately synchronized to disk
(no memory caching allowed).

z z a: the file can only be appended (data is added to the file); changes are not allowed to
existing content. Very useful for log files.

Did u know? Another very interesting attribute is the immutable flag (i) that doesn’t allow
the file to be deleted, changed, modified, renamed or moved.

Self Assessment

Fill in the blanks:
4. The ...................................... command by itself, without any arguments, shows you a list of
mounted file systems.

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