Another important part of the kernel is the PROC file system.
PROC is a so-called pseudo file system
that is used as an interface to the kernel.
You can use it to get information
about different kernel-related parts
and also to optimize kernel settings.
We already talked about it a little bit.
Status files are provided in the slash PROC directory
and information about processes can
be obtained from the PID directories in PROC PID.
And also, there is kernel tunables
that are provided in PROC SYS.
If you want to get information about these kernel parameters,
read the MAN page, MAN 5 PROC.
And if you want to get more information,
consider installing the kernel documentation
using dnfinstallkernel-doc.
And you can access it through usershare-doc kernel-doc.
Let me show you what you can find in the PROC file system.
Now, do realize that this PROC file system has
a lot of options.
Don't dive into it too deeply.
It's not that important for RHCSA.
So let me get in the PROC file system.
And let me also type mountpipegrabPROC,
where we can see that the device PROC is mounted on slash PROC
and the type is PROC.
Now, the device PROC, it doesn't have a real device name.
And that means that it's a kernel interface.
That also means that when I try to do a common operation
like touch hello, which normally would create an empty file
with the name hello, well, in PROC, that doesn't work.
It's not a real file system.
But it's very convenient for finding what is going on.
We have already seen meminfo, for instance,
for finding information, deeply detailed information
about what's going on in your memory.
There is, for instance, the file CPU info,
which is giving information about the CPUs
that you are using and the different features that
are provided for your CPU.
And more of these status files are to the right
of the output of PROC.
Then we have the PID directories.
If I go into a random PID directory like 1577,
then I want to know what it is, right?
Well, I'm going to do a CAT on the CMD line.
And CMD line is giving me nothing.
That means that 1577 was not a very good choice, probably
a kernel process.
Trying another random process, 3084.
And CAT on CMD line is showing that that is GSDX settings.
All right.
And in this PID directory, we have the status file.
And in this status file, you can find what exactly
this process is doing.
Deep going usage information about the processes
are mined from here.
Now, the nice thing is that in order to work with PROC,
you have front-end utilities.
But sometimes, the front-end utility doesn't go deep enough.
And for that reason, it can be convenient to find
your information in PROC.
Don't overestimate PROC for your RHTSA.
Just the generic knowledge of what is going on
is more than enough.
You're not going to be asked to do any kernel optimization
through PROC.