Questions about setting up a new computer

[Sam Hartman]

>>>>> "John" == John J Boyer <john.boyer at abilitiessoft.org> writes:

    John> I've more or less decided to replacer my ten-year-old Linux
    John> machine. It is giving error messages intermittently. Most of
    John> them are about sector errors, but others seem to have nothing
    John> to do with the hard drive. It may be more and more
    John> troublesome, even if the hard drive is replaced.  Besides, it
    John> would be nice to get more up-to-date hardware.

    John> I'm thinking of getting 32 GB of ram. 8 GB will be for normal
    John> use. The other 24 GB will be in a ramdisk.

I think you must have a DOS background here.
An explicit RAM disk is rarely if ever useful on Linux.  I'm tryinfg to
remember if I even know how to create a block device backed by RAM... O,
yeah, I can think of a way,  but you probably don't want to do that.

Instead, you probably do want to create something called a tmpfs.
That's a filesystem backed by RAM.  When your computer reboots all its
contents go away.

There are important differences between a tmpfs and a RAM disk.
The biggest is that Linux will only use as much RAM as is needed by the
tmpfs to store what currently lives in it.
(You can set a maximum size, but with 32g I wouldn't bother)

So, you can get the best of both worlds, storing your temporary files in
RAM, but using RAM for RAM if you don't have 24G of temporary files at
the moment.


    John> Do I need a paging
    John> file? 8 GB of available ram should be more than enough. The
    John> paging file on my present machine always shows 0 usage, even
    John> with only 4 GB of ram.


Having a paging file has a couple of affects even if it is not used, but
no, you probably don't want a swap partition or file (linux names for
paging)

    John> How do I avoid setting up a paging file
    John> during installation? I'm using Debian Jessie.

In expert mode, avoid creating a swap partition and if asked don't
create a swap file.
If you don't want to use expert mode, don't worry about it; having a
swap partition won't be a problem.

    John> How do i set up the ramdisk? I want to assign the temp
    John> directory to it.  

I think the installer will do that by default.
But in /etc/fstab you want a line like

none				/tmp			tmpfs				defaults		0	0

    John> It might be nice if the
    John> bin, sbin and usr
    John> directories were loaded onto it at boot-up.

No need for that.
Linux is also smart enough to cache files  as they are used, storing
copies in memory, so no value in moving them to the tmpfs.

The file will be loaded the first time it is used.
You could do that at boot for /bin, /sbin and /usr, but you probably
don't want to.  The reason is that the system is fairly busy at boot,
and it would probably slow down things like bringing up your desktop and
starting system services.  The only advantage of pre-caching files on
boot would be faster performance the first time you accessed a program
after pre-caching is done.  However you get slower boot times and slower
performance during the pre-caching.