VCN: 2nd (and subsequent) ubuntu gnome desktops

Often when remote accessing the gnome desktop of a linux machine, the physical desktop of the local machine is not necessarily the one that you want use. eg there is already a user on that desktop, or the resolution of the local monitor is often too large for comfortable vnc use.

So: in addition to using the gnome 'remote desktop' feature (which uses vinagre btw), install in addition vnc4server:
apt-get install vnc4server
when using a vnc viewer, the default display (:0) will be accessed when you run:
vncviewer
when vnc4server is additionally installed running the command
vncserver
will start up a 2nd desktop accessible thus:
vncviewer 192.168.1.1:1
each time the command is run another desktop is set running; the desktop number increments each time, as does the port number (desktop:0 starts at 5900 by default)
The type of desktop is setup in the file: ~/user/.vnc/xstartup and by default the twm type desktop is not much help.
To edit the xstartup file (using nano) so that it will start up a regular gnome desktop add this:
#!/bin/sh

# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc

#[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
#[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
#xsetroot -solid grey
#vncconfig -iconic &
#xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &

unset SESSION_MANAGER
sh /etc/X11/xinit/xinitrc

If you've just edited the above and had previously set a desktop:1 running, stop it with:
vncserver -kill :1
then start the server again. When accessing this time you should have a regular gnome desktop.

Sometimes I've had trouble using the gnome desktop over VNC, whereby the menus don't show/dropdown on the client machine. Changing the 'appearance' setting to visual enhancements = none (under system-> preferences) on the server side has usually sorted this.

gnome system monitor. drive space 'free' but not 'available'

this is to do with 'reserved blocks'. Maybe something to do with reserving a percentage of space for root to access the drive should it get full. below changes that percentage to 0. Could replace 0 with 1 I guess?

correct with
markp@server:~$ sudo tune2fs -m 0 /dev/sdc1

vnc of second desktops at different resolutions

markp@markp-eee:~$ vncserver

You will require a password to access your desktops.

Password:
Verify:

New 'markp-eee:1 (markp)' desktop is markp-eee:1

Creating default startup script /home/markp/.vnc/xstartup
Starting applications specified in /home/markp/.vnc/xstartup
Log file is /home/markp/.vnc/markp-eee:1.log

making samba a pdc

Number of things needed:

to add the xp machines, create unix accounts automatically, this examples need a a unix group called machines to work:

add machine script = /usr/sbin/useradd -g machines -c "%u machine account" -d /var/lib/samba -s /bin/false %u

converting flv's to mpeg's

The following takes an flv in folder /music and outputs it as an mpg in the home folder

markp@server:~$ ffmpeg -i /music/faithworks.flv -sameq -s 480x270 faithworks.mpg

Merging pdf's

Ghostscript does this simply:

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=crossing_grant_application_v1.pdf cover.pdf doc1.pdf appa.pdf appb.pdf appc.pdf appe.pdf

webgen

Webgen creates websites with linked menus, common stylesheets and template and page files which work as site wide models. It does this automatically using perl scripting.

create a new site:
cd into directory that will hold new site.
webgen create -t default -s andreas08 mysite
on a default installation you choose between three templates -t and several styles applied to those templates -s
when created cd into your new website top level folder (eg mysite) and run command 'webgen' to create the static html content. The html created resides in a subfolder called 'output'. Run same command each time any changes are made. Content of the output folder is what needs ftp'ing to your webserver. Seeemples.

mdadm on existing setup

These notes relate to my ubuntu 9.10 setup. When I first setup up I had two sata drives (sda1 and sdb1) and an IDE drive (sdc1). sdb1 was one of an intended pair of 750gb drives that I wanted to set up as RAID1 using mdadm for /home, however the 2nd of that pair went back to samsung and was replaced under warranty at the time of setting up the 9.10 machine. The challenge here was could I add the 2nd 750gb drive, create the RAID and transfer what was on original /home as a regular ext3, without having to totally start over. Short answer - yes!

First let's see what's happening with the drives:
root@server:~# fdisk -l

The new drive is placed as /dev/sdb. The previous sdb1 (/home) gets renamed to /dev/dsc1 and the IDE goes to sdd1. As my fstab is using UUID's this presents no problem. To prepare the new drive
root@server:~# fdisk /dev/sdb
This brings up the fdisk command prompt: use n for new partition; partition type is 'fd' for linux raid.

To manage what I want to do I need to setup an mdadm raid1 array without the 2nd drive in place:
root@server:~# mdadm --create --force --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 missing
Result:
mdadm: size set to 732571904K
mdadm: array /dev/md0 started.

OK, lets check what's happening with mdadm:
root@server:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb1[0]
732571904 blocks [2/1] [U_]

unused devices: none

OK, format the new array drive with:
root@server:~# mkfs.ext3 /dev/md0

create info for the mdadm config file with:
root@server:~# mdadm --detail --scan --verbose > /etc/mdadm/mdadm.conf

Mount the new array (/dev/md0) as /whatever
root@server:~# mkdir /whatever
root@server:~# mount /dev/md0 /whatever

Copy contents of /home to /whatever.
-a is archive, preserves all attributes; -v verbose, let's you know what's happening:
root@server:~# cp -a -v /home/* /whatever

unmount the old /home:
root@server:~# umount /home

OK so now use fdisk again change the partition type of sdc1 to fd as above,
then add sdc1 to the array with
root@server:~# mdadm --add /dev/md0 /dev/sdc1

Next check that the new array can mount manually:
root@server:~# mount /dev/md0 as /whatever
OK!

Problem: after a reboot there doesn't appear to be a /dev/md0 Where's it gone?! Don't worry it's become /dev/md_d0 instead. This is the new naming convention which mdadm uses on newer linux kernels that can make md devices partitionable (see mdadm MAN on this).

Next issue is that /dev/md_d0 will need mounting as /home using fstab. Using the UUID that the mdadm --scan command uses appears not to be the right one. Using the command blkid (Block ID) gives another UUID for the RAID partition itself. Use that in fstab.

STUCK AT PRESENT
Can't get the raid drive to mount using fstab:
First of all simply tried hashing out the old /home and using the new raid drive, the UUID for the raid device is the one that blkid is giving me. like this:
# orig /home was on /dev/sdb1 during installation
#UUID=e2c6ff62-a576-4182-b5e0-82c9fea9601c /home ext2 relatime $

# raid /home on /dev/md_d0 created during raid setup
UUID=9c1a494c-0e38-4f3b-b1f1-cdf66f4e7c0a /home ext3 relatime $

No go, so I also try this:
# orig /home was on /dev/sdb1 during installation
#UUID=e2c6ff62-a576-4182-b5e0-82c9fea9601c /home ext2 relatime $

# raid /home on /dev/md_d0 created during raid setup
/dev/md_d0 /home ext3 relatime 0 $

Still no go; boot halts saying that /home cannot be mounted.
OK that could because I can't simply switch the /home directory without doing some other things perhaps. So let's just try and get the raid to mount as /whatever:
# raid /home on /dev/md_d0 created during raid setup
UUID=9c1a494c-0e38-4f3b-b1f1-cdf66f4e7c0a /whatever ext3 relatime $
This results in /whatever being empty?
Huh?

this works:
markp@server:~$ sudo mount /dev/md_d0 /whatever

So does this:
markp@server:~$ sudo mount UUID="9c1a494c-0e38-4f3b-b1f1-cdf66f4e7c0a" /whatever

OK So John thinks there's something squiffy with my fstab. knocking the options off of it and doing a mount -a indicates that might be right.

However rebooting fstab doesn't mount /whatever, but after boot 'mount -a' does add it in. This makes me think the raid is not ready to be mounted at initial boot time perhaps?

Unstuck - ie got it working!

When I finally freed up the second 750gb drive from it's /home duties I tried to add it to the /dev/md_d0 raid drive. No joy. Lot's of attempts, including changing the format of the drives to ext4.

Got it fixed by simply running the create again, with force. Done away with all the faffy partition stuff by adding --auto=md This creates an (old fashioned?) regular /dev/md0
Complains that sdb1 and sdc1 are part of a raid and had a ext2 and ext3 partition (I'd definately tried to change them from that??). Anyway this time the new ext4 /dev/md0 is working OK.

root@server:~# mdadm --create --force --verbose --auto=md /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1

Now to copy /home to it then mount it as new /home. Then see if the new install (10.04) will see the raid from install (using server version)