Wednesday, June 29, 2011

Flash File System ---- Linux

[1] http://en.wikipedia.org/wiki/LogFS
[2] http://en.wikipedia.org/wiki/JFFS2
[3] http://en.wikipedia.org/wiki/YAFFS
[4] http://en.wikipedia.org/wiki/Flash_file_system
[5] http://www.linux-mtd.infradead.org/faq/jffs2.html#L_bbhandle ----jffs2 trouble shotting


LOGFS IS THE FUTURE FOR BIGGER FLASH [1]
----------------------------------------
LogFS is a Linux log-structured and scalable flash filesystem, intended for use on large devices of flash memory. It is written by Jörn Engel and in part sponsored by the CE Linux Forum.

LogFS is included in the mainline Linux kernel and was introduced in version 2.6.34, released on May 16, 2010.


DISADVANTAGE OF JFFS2 [2]
-------------------------------
Disadvantages

All nodes must still be scanned at mount time. This is slow and is becoming an increasingly serious problem as flash devices scale upward into the Gigabyte range.
Writing many small blocks of data can even lead to negative compression rates, so it is essential for applications to use large write buffers.
There is no practical way to tell how much usable free space is left on a device since this depends both on how well additional data can be compressed, and the writing sequence.

Tuesday, June 28, 2011

Check package version under Ubuntu

[1] http://www.howtogeek.com/howto/ubuntu/see-what-version-of-a-package-is-installed-on-ubuntu/


quentin@ubuntu:/var/lib/tftpboot$ dpkg -s mtd-utils
Package: mtd-utils
Status: install ok installed
Priority: extra
Section: utils
Installed-Size: 1160
Maintainer: Ubuntu Developers
Architecture: i386
Version: 20100706-1
Replaces: mtd-tools
Provides: mtd-tools
Depends: libc6 (>= 2.8), liblzo2-2, libuuid1 (>= 2.16), zlib1g (>= 1:1.1.4)
Description: Memory Technology Device Utilities
Utilities for manipulating memory technology devices, such as flash
memory, Disk-On-Chip, or ROM. Includes mkfs.jffs2, a tool to create
JFFS2 (journaling flash file system) filesystems.
Original-Maintainer: Riku Voipio
Homepage: http://www.linux-mtd.infradead.org/

Monday, June 20, 2011

VNC Server set up in UBUNTU

[1] http://theseekersquill.wordpress.com/2010/03/16/vnc-server-ubuntu-windows/ ---Best Link
[2] http://nuclear-imaging.info/site_content/2010/04/19/vnc-server-setup-for-ubuntu-10-04-lucid-lynx/
[3] http://usingnix.wordpress.com/2010/12/15/setup-vnc-in-ubuntu-10-10/
[4] http://blog.sudobits.com/2011/03/13/vnc-server-for-ubuntu-10-10/
[5] http://ubuntuforums.org/showthread.php?t=1313898 ---- Get rid of warning for auto start
[6] http://www.debianhelp.co.uk/vnc.htm
[7] http://askubuntu.com/questions/390113/x11vnc-much-slower-than-xvnc-how-to-get-a-xubuntu-session-manually
[8] https://freevps.us/thread-14110.html
[9] https://help.ubuntu.com/community/VNC/Servers
[10] https://wiki.archlinux.org/index.php/TigerVNC  
[11] http://askubuntu.com/questions/603169/lubuntu-14-04-tightvnc-remote-mouse-cursor-is-x

[12] vnc/xrdp to xfce4  windows manager good posts
[13] Using ubuntu 14.04.3 default vino desktop sharing (current session)
[14] One bug fix in early 14.04 vino

qyang@lubuntu-laptop:~$ apt-cache search autocutsel
autocutsel - Keep the X clipboard and the cutbuffer in sync

Got tightvnc work on lubuntu after changing xstartup file
./vnc/xstartup file is configured as follows [11] :


#!/bin/sh

xrdb $HOME/.Xresources
xsetroot -solid grey -cursor_name left_ptr
autocutsel -fork
lxsession -s Lubuntu -e LXDE
 

x11vnc is slower. [7] [8] tightvncserver is suggested and faster. [8] vnc4server was discussed a lot.

x11vnc is different from xvnc(tightvnc, tigervnc). The latter support multiple sessions. Also, seems x11vnc is slower than xvnc.[7]
x11vnc offers better security focus ( can be secured with SSH or SSL.) but it's known to be slower. [8]


vino and x11vnc in Ubuntu [9]


VNC SET UP AND SSH SERVER SET UP
-----------------------------------

INSTALL OPENSSH SERVER AND VNC SERVER
----------------------------------------
quentin@QuentinUbuntu:~$ sudo apt-get install openssh-server openssh-client vnc4server xinetd vncviewer
[sudo] password for quentin:
Sorry, try again.
[sudo] password for quentin:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'xtightvncviewer' instead of 'vncviewer'
The following extra packages will be installed:
xbase-clients xtightvncviewer
Suggested packages:
libpam-ssh keychain openssh-blacklist openssh-blacklist-extra rssh
molly-guard vnc-java tightvncserver
The following NEW packages will be installed:
openssh-server vnc4server xbase-clients xinetd xtightvncviewer
The following packages will be upgraded:
openssh-client
1 upgraded, 5 newly installed, 0 to remove and 328 not upgraded.
Need to get 3,305kB of archives.
After this operation, 6,484kB of additional disk space will be used.
Do you want to continue [Y/n]? Y
....................
.............


SSH SERVER SET UP
--------------------------------------------
quentin@QuentinUbuntu:~$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/quentin/.ssh/id_rsa):
Created directory '/home/quentin/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/quentin/.ssh/id_rsa.
Your public key has been saved in /home/quentin/.ssh/id_rsa.pub.
The key fingerprint is:
9f:71:93:c0:80:9f:aa:e5:a9:ec:e1:0c:d2:9a:a3:13 quentin@QuentinUbuntu
The key's randomart image is:
+--[ RSA 2048]----+
| .. |
| . o |
| . .o |
| o . . |
| .S . + |
|E. o . + . |
|..o .+ . o |
|o+ =..o |
|=o .*. |
+-----------------+

SET UP VNC SERVER PASSWORD
--------------------------------------
qyang@lubuntu-laptop:~$ vncpasswd
Using password file /home/qyang/.vnc/passwd
VNC directory /home/qyang/.vnc does not exist, creating.
Password:
Verify: 
Would you like to enter a view-only password (y/n)? y
Password:
Verify: 



START VNC SERVER
-----------------------------
quentin@QuentinUbuntu:~$ vnc4server

New 'QuentinUbuntu:1 (quentin)' desktop is QuentinUbuntu:1

Creating default startup script /home/quentin/.vnc/xstartup
Starting applications specified in /home/quentin/.vnc/xstartup
Log file is /home/quentin/.vnc/QuentinUbuntu:1.log


quentin@QuentinUbuntu:~$ ps aux |grep vnc
quentin 1898 0.1 0.3 10504 5284 pts/0 S 19:07 0:00 Xvnc4 :1 -desktop QuentinUbuntu:1 (quentin) -auth /var/run/gdm/auth-for-quentin-5eao3N/database -geometry 1024x768 -depth 16 -rfbwait 30000 -rfbauth /home/quentin/.vnc/passwd -rfbport 5901 -pn -fp /usr/X11R6/lib/X11/fonts/Type1/,/usr/X11R6/lib/X11/fonts/Speedo/,/usr/X11R6/lib/X11/fonts/misc/,/usr/X11R6/lib/X11/fonts/75dpi/,/usr/X11R6/lib/X11/fonts/100dpi/,/usr/share/fonts/X11/misc/,/usr/share/fonts/X11/Type1/,/usr/share/fonts/X11/75dpi/,/usr/share/fonts/X11/100dpi/ -co /etc/X11/rgb
quentin 1904 0.0 0.0 4596 1540 pts/0 S 19:07 0:00 vncconfig -iconic
quentin 1936 0.0 0.0 4008 748 pts/0 S+ 19:09 0:00 grep --color=auto vnc

KILL VNCSERVER
------------------------
quentin@QuentinUbuntu:~$ vncserver -kill :1
Killing Xvnc4 process ID 3561

LOCAL VNC ACCESS
-----------------------
quentin@QuentinUbuntu:~$vncviewer localhost:1

SSH SERVER LOG IN VIA PUTTY
-------------------------------
quentin@10.1.1.5's password:
Linux QuentinUbuntu 2.6.35-22-generic #33-Ubuntu SMP Sun Sep 19 20:34:50 UTC 2010 i686 GNU/Linux
Ubuntu 10.10

Welcome to Ubuntu!
* Documentation: https://help.ubuntu.com/

Your CPU appears to be lacking expected security protections.
Please check your BIOS settings, or for more information, run:
/usr/bin/check-bios-nx --verbose

336 packages can be updated.
157 updates are security updates.

New release 'natty' available.
Run 'do-release-upgrade' to upgrade to it.


The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.


EDIT VNC XSTARTUP FILE TO REMOVE GREY BACKGROUND
------------------------------------------------
quentin@QuentinUbuntu:~$ vi /home/quentin/.vnc/xstartup

#!/bin/sh

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

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

#x-window-manager &

#gnome-session &
#twm &

START VNC SERVER AGAIN
----------------------------------
quentin@QuentinUbuntu:~$ vncserver
xauth: creating new authority file /home/quentin/.Xauthority

New 'QuentinUbuntu:1 (quentin)' desktop is QuentinUbuntu:1

Starting applications specified in /home/quentin/.vnc/xstartup
Log file is /home/quentin/.vnc/QuentinUbuntu:1.log


MAKE VNC SERVER AUTO RUN WHEN BOOT
------------------------------------
$sudo -i

root@QuentinUbuntu:~# vi /etc/init.d/vncserver

#!/bin/sh -e

### BEGIN INIT INFO
# Provides: vncserver
# Required-Start: networking
# Default-Start: S
# Default-Stop: 0 6
### END INIT INFO

PATH="$PATH:/usr/X11R6/bin/"

# The Username:Group that will run VNC
export USER="quentin"
#${RUNAS}

# The display that VNC will use
DISPLAY="1"
# Color depth (between 8 and 32)
DEPTH="16"
# The Desktop geometry to use.
#GEOMETRY="x"
#GEOMETRY="800x600"
GEOMETRY="1024x768"
#GEOMETRY="1280x1024"
# The name that the VNC Desktop will have.
NAME="QuentinUbuntu-vnc-server"
OPTIONS="-name ${NAME} -depth ${DEPTH} -geometry ${GEOMETRY} :${DISPLAY}"
. /lib/lsb/init-functions

case "$1" in
start)
su ${USER} -c "/usr/bin/vncserver ${OPTIONS}"
;;
stop)
su ${USER} -c "/usr/bin/vncserver -kill :${DISPLAY}"
;;
restart)
$0 stop
$0 start
;;
esac
exit 0

root@QuentinUbuntu:~# chmod +x /etc/init.d/vncserver

MAKE IT AUTO RUN WHEN BOOT
-----------------------------------
sudo update-rc.d vncserver defaults
update-rc.d: warning: /etc/init.d/vncserver missing LSB keyword 'required-stop'

update-rc.d: warning: vncserver start runlevel arguments (2 3 4 5) do not match LSB Default-Start values (S)
update-rc.d: warning: vncserver stop runlevel arguments (0 1 6) do not match LSB Default-Stop values (0 6)
Adding system startup for /etc/init.d/vncserver ...
/etc/rc0.d/K20vncserver -> ../init.d/vncserver
/etc/rc1.d/K20vncserver -> ../init.d/vncserver
/etc/rc6.d/K20vncserver -> ../init.d/vncserver
/etc/rc2.d/S20vncserver -> ../init.d/vncserver
/etc/rc3.d/S20vncserver -> ../init.d/vncserver
/etc/rc4.d/S20vncserver -> ../init.d/vncserver
/etc/rc5.d/S20vncserver -> ../init.d/vncserver
To get rid of warning

we change the /etc/init.d/vncserver

### BEGIN INIT INFO
# Provides: vncserver
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start daemon at boot time
# Description: Enable service provided by daemon.
### END INIT INFO

quentin@QuentinUbuntu:~$ sudo update-rc.d -f vncserver remove
Removing any system startup links for /etc/init.d/vncserver ...
/etc/rc0.d/K20vncserver
/etc/rc1.d/K20vncserver
/etc/rc2.d/S20vncserver
/etc/rc3.d/S20vncserver
/etc/rc4.d/S20vncserver
/etc/rc5.d/S20vncserver
/etc/rc6.d/K20vncserver

NO MORE WARNINGS
--------------------------------
quentin@QuentinUbuntu:~$ sudo update-rc.d vncserver defaults
Adding system startup for /etc/init.d/vncserver ...
/etc/rc0.d/K20vncserver -> ../init.d/vncserver
/etc/rc1.d/K20vncserver -> ../init.d/vncserver
/etc/rc6.d/K20vncserver -> ../init.d/vncserver
/etc/rc2.d/S20vncserver -> ../init.d/vncserver
/etc/rc3.d/S20vncserver -> ../init.d/vncserver
/etc/rc4.d/S20vncserver -> ../init.d/vncserver
/etc/rc5.d/S20vncserver -> ../init.d/vncserver