raldi's questions

$ ls
bash: no more processes

Uh oh. Looks like someone made a fork bomb. Where I used to work, this pretty much meant that the shared server would need to be power-cycled, since even the sysadmins with root often couldn't get the problem cleaned up. Often, they couldn't even get a prompt.

I've heard a few tricks (notably, to send STOP signals rather than KILL signals, since the latter would allow the remaining threads to immediately replace the killed ones), but I've never seen a comprehensive guide entitled So, You Have Yourself a Fork Bomb?

Let's make one.

I've got an Ubuntu server that boots up in text mode. It rarely has a screen or keyboard attached to it, but when I do attach a screen, I usually have to attach a keyboard too, because the darn console mode screen saver will be on and I'll need to hit a key to see what's going on.

I'm aware that the setterm command can disable this, but it's a per-session thing. How can I make it so the machine never ever blanks the screen in text mode, even when it's first booted up and sitting at the login prompt?

I'm trying to install a driver for a USB DAQ box, which annoyingly, I have to compile myself. I believe I've succeeded -- I have two .ko files:

-rw-r--r--  1 root  root  45271 2010-03-18 21:24 advdrv_core.ko
-rw-r--r--  1 root  root  24312 2010-03-18 21:24 usb4761.ko

I was able to run insmod on the first without incident, but when I try on the second, I get a flood of messages:

kernel: [686782.106547] usb4761: no symbol version for adv_process_info_check_event
kernel: [686782.106555] usb4761: Unknown symbol adv_process_info_check_event
kernel: [686782.106691] usb4761: no symbol version for advdrv_unregister_driver
kernel: [686782.106695] usb4761: Unknown symbol advdrv_unregister_driver

However, advdrv_core.ko provides these symbols. My kernel sure seems to have them in memory:

# cat /proc/kallsyms | grep advdrv_unregister_driver
f8d88504 r __ksymtab_advdrv_unregister_driver   [advdrv_core]
f8d888d2 r __kstrtab_advdrv_unregister_driver   [advdrv_core]
f8d885a4 r __kcrctab_advdrv_unregister_driver   [advdrv_core]
086eb8fb a __crc_advdrv_unregister_driver       [advdrv_core]
f8d86e90 t advdrv_unregister_driver     [advdrv_core]

Why does my insmod claim they're unknown symbols?

Edit: One of the answers below advised me to copy the files to /lib/modules and run depmod. So I did, using depmod's -v (verbose) option. Among the output were a bunch of lines like:

/lib/modules/2.6.27-7-generic/kernel/drivers/pcmcia/usb4761.ko needs "advdrv_unregister_driver": /lib/modules/2.6.27-7-generic/kernel/drivers/pcmcia/advdrv_core.ko

Then I ran rmmod advdrv_core to make sure I was installing it fresh, ran modprobe advdrv_core, and finally ran modprobe usb4761.

Again, a bunch of failed symbols, including advdrv_unregister_driver.

I came across a question today asking for good Linux xterm fonts, and an answer suggests one called Terminus. I've been looking for a new terminal font for a while now, so I downloaded it (BTW, I'm running Ubuntu Intrepid) and read the README:

1.1. Quick installation.
The commands:
  $ ./configure [--prefix=PREFIX]
  $ make
  # make install
compile and install the Linux console and X11 Window System fonts, and
  # make fontdir
updates fonts.dir for X11 (if you don't know what fonts.dir is, execute the
command).

1.2. Legend.    
The file names are structured as follows: ter-u<SIZE><STYLE>.bdf    
where <SIZE> is 12, 14, 16, 20, 24, 28 or 32, and <STYLE> is n for normal
(all sizes), b for bold (all sizes except 6x12) and v for EGA/VGA bold (8x14
and 8x16 only, makes use of the eight character matrix column).

So I ran:

$ ./configure
$ make
$ sudo make install
$ sudo make fontdir

...and I restarted X11 just to be sure, and the new font was nowhere to be found:

$ xterm -font ter-u14n
xterm:  unable to open font "ter-u14n", trying "fixed"....

Sigh. Back to the README. Later in this file, I saw:

4. X11 Window System.
4.1. Installation.

$ ./configure [--prefix=PREFIX | --x11dir=DIRECTORY]
$ make pcf
# make install-pcf

Well, I know that "xterm -font 8x16" works, so I ran "locate 8x16" and saw that this font seemed to live in /usr/share/fonts/X11/misc, so that seemed like a good --x11dir to use. So I ran:

$ ./configure --x11dir=/usr/share/fonts/X11/misc
$ make pcf
$ make install-pcf
$ sudo make fontdir

...and I restarted X11 again, and even my whole computer just for good measure, and I even verified that there were now a bunch of files like /usr/share/fonts/X11/misc/ter-u14n.pcf.gz on my system, but still:

$ xterm -font ter-u14n
xterm:  unable to open font "ter-u14n", trying "fixed"....

What is the magical incantation I have to perform in order to get this font working with xterm?

There's a directory underneath my homedir called ".gvfs". As my regular user account, I can read it just fine:

~ $ ls -lart ~raldi/.gvfs
total 4
dr-x------  2 raldi raldi    0 2009-05-25 22:17 .
drwxr-xr-x 60 raldi raldi 4096 2009-05-25 23:08 ..
~ $ ls -d ~raldi/.gvfs
dr-x------ 2 raldi raldi 0 2009-05-25 22:17 /home/raldi/.gvfs

However, as root I can't "ls" or even "ls -d" it:

# ls ~raldi/.gvfs
ls: cannot access /home/raldi/.gvfs: Permission denied
# ls -d ~raldi/.gvfs
ls: cannot access /home/raldi/.gvfs: Permission denied

And, just to make sure:

# echo $UID $EUID
0 0

This is just a simple home installation of Ubuntu 8.10, no NFS or anything weird like that. I see that the directory is marked non-world-readable (and non-world-x-able), but I thought none of that applied when you're root. For example, I can make a mode-000 directory in /tmp and give it away to a non-root user, and root has no trouble reading it, writing it, whatever.

Any idea what's going on?

With standard PCs, does any modern RAM generally work with any modern motherboard, so long as they can physically interconnect?

If not, is there a table I can consult?