GKrellM - GNU (or Gtk) Krell Monitors (or Meters)
=======================================================================

Author:	Bill Wilson
Email:  billw--at--gkrellm.net
Homepage: https://gkrellm.srcbox.net

Copyright (c) 1999-2021 by Bill Wilson.  This program is free software
which I release under the GNU General Public License.
Read the COPYRIGHT file for more info.

CREDITS: See the CREDITS file.

Description
===========
With a single process, GKrellM manages multiple stacked monitors and supports
applying themes to match the monitors appearance to your window manager,
Gtk, or any other theme.


GKrellM Features
================
	* SMP CPU, Disk, Proc, and active net interface monitors with LEDs.
	* Internet monitor that displays current and charts historical port hits.
	* Memory and swap space usage meters and a system uptime monitor.
	* File system meters show capacity/free space and can mount/umount.
	* A mbox/maildir/MH/POP3/IMAP mail monitor which can launch a mail reader
	  or remote mail fetch program.
	* Clock/calendar and hostname display.
	* Battery laptop battery monitor.
	* CPU/motherboard temperature/fan/voltages display with warnings and
	  alarms.  Linux requires a sensor configured sysfs, lm_sensors modules or
	  a running mbmon daemon.  FreeBSD can also read the mbmon daemon.
	  Windows requires MBM or SpeedFan.
	* Disk temperatures if there's a running hddtemp daemon.
	* Multiple monitors managed by a single process to reduce system load.
	* A timer button that can execute PPP or ISDN logon/logoff scripts.
	* Charts are autoscaling with configurable grid line resolution, or
	  can be set to a fixed scale mode.
	* Separate colors for "in" and "out" data.  The in color is used for
	  CPU user time, disk read, forks, and net receive data.  The out color
	  is used for CPU sys time, disk write, load, and net transmit data.
	* Commands can be configured to run when monitor labels are clicked.
	* GKrellM is plugin capable so special interest monitors can be created.
	* Data can be collected from a gkrellmd server running on a remote machine.
	* Many themes are available.


User Interface
==============
	* Top frame:
		Btn 1   - Press and drag to move gkrellm window.
		Btn 3   - Popup main menu.
	* Side frames:
		Btn 2   - Slide gkrellm window shut (Btn1 if -m2 option).
		Btn 3   - Popup main menu.
	* All charts
		Btn 1   - Toggle draw of extra info on the chart.
		Btn 3   - Brings up a chart configuration window.
	* Inet charts
		Btn 2	- toggle between port hits per minute and hour.
	* Most panels
		Btn 3   - Opens the configuration window directly to a monitor's
		          configuration page.
	* File System meter panels:
		Btn 1,2	- Toggle display of label and fs capacity scrolling display.
		          The mount button runs mount/umount commands.  If ejectable,
		          left click the eject button to open tray, right click closes.
	* Mem and Swap meter panels:
		Btn 1,2	- Toggle display of label and memory or swap capacity
	              scrolling display.
	* Mailbox monitor message count button:
		Btn 1	- Launch a mail reader program.  If options permit, also
	              stop animations and reset remote message counts.
		Btn 2	- Toggle mail check mute mode which inhibits the sound
	              notify progra, and optionally inhibits all mail checking.
	* Mailbox monitor envelope decal:
		Btn 1	- Force a mail check regardless of mute or timeout state.
	* Battery monitor panel:
		Btn 1	- On the charging state decal toggles battery minutes left,
	              percent level, and charge rate display.
		Btn 2	- Anywhere on the panel also toggles the display.

  Keyboard shortcuts:
	* F1  = popup the user config window.
	* F2  = popup the main menu.
	* Page_Up        - previous theme or theme alternative.
	* Page_Down      - next theme or theme alternative.
	* <Ctl>Page_Up   - previous theme, skipping any theme alternatives.
	* <Ctl>Page_Down - next theme, skipping any theme alternatives.

    If a command has been configured to be launched for a monitor, then
    a button will appear when the mouse enters the panel of that monitor.
    Clicking the button will launch the command.


Requirements
============
To use or compile GKrellM, you need:
	* GTK 2 >= 2.24
	* OpenSSL >= 1.1.0 or GnuTLS >= 3.3.0 (optional, for email monitoring)
	* libntlm (optional, for email monitoring)
	* libsensors (optional, for hardware sensors on Linux)

To compile, you need a C99-capable C compiler and development files for
these requirements.


Installation
============
See the INSTALL file.  BSD systems will need to use GNU gmake.


Running GKrellM
===============
To get a list of options:

	gkrellm --help

Some of the options are:
	-t, --theme  theme_dir
	   GKrellM will load all theme image files it finds in theme_dir
	   and parse the gkrellmrc file if one exists.  This option overrides
	   the loading of the last theme you configured to be loaded in
	   the Themes configuration window.  Theme changes are not saved
	   when GKrellM is run with this option.
	-g, --geometry +x+y
	   Or -g +x+y.  Makes GKrellM move to an x y position on the screen
	   at startup.  Standard X window geometry position (not size) formats
	   are parsed, ie +x+y -x+y +x-y -x-y.  Except, negative geometry
	   positions are not recognized (ie +-x--y )
	-wm
	   Forces GKrellM to start up with window manager decorations.  The
	   default is no decorations because there are themed borders.
	-w, --withdrawn
	   GKrellM starts up in withdrawn mode so it can go into a window
	   manager's slit.  This should work with the Blackbox, Fluxbox, Kahakai,
	   Waimea, and maybe other window managers with the slit feature.
	-c, --config  suffix
	   Use alternate config files generated by appending "suffix" to config
	   file names.  This overrides any previous host config which may have
	   been setup with the below option.
	-f, --force-host-config
	   If GKrellM is run once with this option and then the configuration
	   or theme is changed, the config files that are written will have
	   a -hostname appended to them.  Subsequent runs will detect the
	   user-config-hostname and gkrellm_theme.cfg-hostname files and use
	   them instead of the normal configuration files (unless the --config
	   option is specified).   This is a convenience for allowing
	   remote GKrellMs independent config files in a shared home directory,
	   and for the hostname to show up in the X title for window management.
	-s, --server hostname
	   Run in client mode by connecting to and collecting data from a gkrellmd
	   server running on "hostname".
	-P, --port server_port
	   Use "server_port" for the gkrellmd server connection.
	-nc
	   No config mode.  The config menu is blocked so no config changes
	   can be made.  Useful in certain environments, or maybe for running
	   on a gdm login screen or during a screensaver mode?
	-demo
	   Force enabling of many monitors so themers can see everything. All
	   config saving is inhibited.
	-p, --plugin  plugin_under_test.so
	   For plugin development, load the command line specified plugin so you
	   can avoid repeated install steps in the development cycle.


Configuring GKrellM
===================

A right button mouse click on the side or top frames of the GKrellM
window will pop up a user configuration window where you can configure
all the builtin and plugin monitors.  Chart appearance may be configured
by right clicking on a chart, and right clicking on many panels will open
the configuration window directly to the corresponding monitor's
configuration page.


Using GKrellM - keeping an eye on your computers Id.
====================================================

Charts
======
The default for most charts is to automatically adjust the number of
grid lines drawn and the resolution per grid so drawn data will be
nicely visible.  You may change this to fixed grids of 1-5 and/or
fixed grid resolutions in the chart configuration windows.  However,
some combination of the auto scaling modes may give best results.

Auto grid resolution has the following behavior.

  If "Auto mode sticks at peak value" is not set:
    1) If using auto number of grids, set the resolution per grid and the
       number of grids to optimize the visibility of data drawn on the chart.
       Try to keep the number of grids between 1 and 7.
    2) If using a fixed number of grids, set the resolution per grid to the
       smallest value that draws data without clipping.

  If "Auto mode sticks at peak value" is set:
    1) If using auto number of grids, set the resolution per grid such that
       drawing the peak value encountered would require at least 5 grids.
    2) If using a fixed number of grids, set the resolution per grid such
       that the peak value encountered could be drawn without clipping.
       This means the resolution per grid never decreases.

All resolution per grid values are constrained to a set of values in
either a 1, 2, 5 sequence or a 1, 1.5, 2, 3, 5, 7 sequence.  If you set
"Auto mode sticks at peak value" a manual "Auto mode recalibrate" may
occasionally be required if the chart data has a wide dynamic range.


CPU Monitor
-----------
Data is plotted as a percentage.  In auto number of grids
mode, resolution is a fixed 20% per grid.  In fixed number of grids
mode, grid resolution is 100% divided by the number of grids.


Proc Monitor
------------
The krell shows process forks with a full scale value
of 10 forks.  The chart has a resolution of 10 forks/sec per grid
in auto number of grids mode and 50 forks/second maximum on the
chart in fixed number of grids mode.
The process load resolution per grid is best left at 1.0 for auto
number of grids, but can be set as high as 5 if you configure the
chart to have only 1 or 2 fixed grids.


Net Monitor
------------
GKrellM is designed to display a chart for net interfaces which are
up, which means they are listed in the routing table (however, it is
possible in some cases to monitor unrouted interfaces).
One net interface may be linked to a timer button which can be used
to connect and disconnect from an ISP.

The timer button shows an off, standby, or on state by a distinctive
(color or shape) icon.
ppp: Standby state is while the modem phone line is locked while
    ppp is connecting, and the on state is the ppp link connected.
    The phone line lock is determined by the existence of the modem
    lock file /var/lock/LCK..modem which assumes pppd is using
    /dev/modem.  However, if your pppd setup does not
    use /dev/modem, then you can configure an alternative with:
         ln  -s  /var/lock/LCK..ttySx   ~/.gkrellm2/LCK..modem
    where ttySx is the tty device your modem does use.  The ppp on
    state is detected by the existence of /var/run/pppX.pid and
    the time stamp of this file is the base for the on line time.
ippp: The timer button standby state is not applicable to isdn
    interfaces that are always routed. The on state is isdn on line
    while the ippp interface is routed.  The on line timer is reset
    at transitions from isdn hangup state to on line state.
For both ppp and ippp timer button links, the panel area of the
interface is always shown and the chart appears when the interface
is routed with the phone link connected or on line.

If the timer button is not linked to a net interface, then it can
be used as a push on / push off timer

Net monitors can have a label so that the interface can be
associated with the identity of the other end of the connection.
This is useful if you have several net connections or run multiple
remote gkrellms.  It can be easier to keep track of who is connected
to who.


Mem and Swap Monitor
--------------------
Here you are reading a ratio of total used to total available.
The amount of memory used indicated by the memory monitor is
actually a calculated "used" memory.  If you enter the
"free" command, you will see that most of your memory is almost
always used because the kernel uses large amounts for buffers
and cache.  Since the kernel can free a lot of this memory
as user process demand for memory goes up, a more realistic reading
of memory in use is obtained by subtracting the buffers and cached
memory from the kernel reported used.  This is shown in the free
command output in the "-/+ buffers/cache" line where a calculated
used amount has buffers and cached memory subtracted from the kernel
reported used memory, and a calculated free amount has the buffers
and cached memory added in.

While the memory meter always shows the calculated "used" memory,
the raw memory values total, shared, buffered, and cached may be
optionally displayed in the memory panel by entering an appropriate
format display string in the config.

Units:  All memory values have units of binary megabytes (MiB).
Memory sizes have historically been reported in these units because
memory arrays on silicon have always increased in size by multiples
of 2.  Add an address line to a memory chip and you double or quadruple
(a multiplexed address) the memory size.  A binary megabyte is
2^20 or 1048576.  Contrast this with units for other stats such
as disk capacities or net transfer rates where the proper units
are decimal megabytes or kilobytes.  Disk drive capacities do not
increase by powers of 2 and manufacturers do not use binary
units when reporting their sizes.  However, some of you may prefer
to see a binary disk drive capacity reported, so it is available
as an option.


Internet Monitor
----------------
Displays TCP port connections and records historical port hits on a
minute or hourly chart.  Middle button click on an inet chart to
toggle between the minute and hourly displays.  There is a strip
below the minute or hour charts where marks are drawn for port
hits in second intervals.  Each inet krell also shows port hits
with a full scale range of 5 hits.  The left button toggle of extra
info displays current port connections.

For each internet monitor you can specify two labeled datasets with
one or two ports for each dataset.  There are two ports because some
internet ports are related and you might want to group them - for
example, the standard http port is 80, but there is also a www web
caching service on port 8080.  So it makes sense to have a http
monitor which combines data from both ports.  A possible common
configuration would be to create one inet monitor that monitors
http hits plotted in the one color and ftp hits in another.
To do this, setup in the Internet configuration tab:

    http  80 8080    ftp  21

Or you could create separate monitors for http and ftp.  Other
monitors might be smtp on port 25 or nntp on port 119.

If you check the "Port0 - Port1 is a range" button, then all of the
ports between the two entries will be monitored.  Clicking the
small button on the Inet panels will pop up a window listing the
currently connected port numbers and the host that is connected
to it.

GKrellM samples TCP port activity once per second, so it is possible
for port hits lasting less than a second to be missed.


File System Monitor
-------------------
File system mount points can be selected to be monitored with a meter
that shows the ratio of blocks used to total blocks available.  Mounting
commands can be enabled for mount points in one of two ways:

1) If a mount point is in your /etc/fstab and you have mount permission
then mount and umount commands can be enabled and executed for that
mount point simply by checking the "Enable /etc/fstab mounting" option.
Mount table entries in /etc/fstab must have the "user" or "owner" option set
to grant this permission unless GKrellM is run as root.
For example, if you run GKrellM as a normal user and you want to be
able to mount your floppy, your /etc/fstab could have either of:
    /dev/fd0  /mnt/floppy  ext2   user,noauto,rw,exec  0  0
or
    /dev/fd0  /mnt/floppy  ext2   user,defaults  0  0

2) If GKrellM is run as root or if you have sudo permission to run the
mount commands, then a custom mount command can be entered into the
"mount command" entry box.  A umount command must also be entered if you
choose this method.  Example mount and umount entries using sudo:
      sudo /bin/mount -t msdos /dev/fd0 /mnt/A
      sudo /bin/umount /mnt/A
Notes: the mount point specified in a custom mount command (/mnt/A in
this example) must be the same as entered in the "Mount Point" entry.
Also, you should have the NOPASSWD option set in /etc/sudoers for this.

File system monitors can be created as primary (always visible)
or secondary which can be hidden and then shown when they are of
interest.  For example, you might make primary file system monitors
for root, home, or user so they will be always visible, but make
secondary monitors for less frequently used mount points such as
floppy, zip, backup partitions, foreign file system types, etc.
Secondary FS monitors can also be configured to always be visible if they
are mounted by checking the "Show if mounted" option.   Using this
feature you can show the secondary group, mount a file system, and have
that FS monitor remain visible even when the secondary group is hidden.
A standard cdrom mount will show as 100% full but a monitor for it
could be created with mounting enabled just to have the
mount/umount convenience.

When the "Ejectable" option is selected for a file system, an eject
button will appear when the mouse enters the file system panel.  If you
are not using /etc/fstab mounting, a device file to eject will also need
to be entered.  Systems may have varying levels of support for this feature
ranging from none or basic using an ioctl() to full support using an eject
command to eject all its supported devices.   Linux and NetBSD use the
"eject" command while FreeBSD uses the "cdcontrol" command, so be sure
these commands are installed.
Most eject commands will also support closing a CDROM tray.  If they do,
you will be able to access this function by right clicking the eject button.


Mail Monitor
------------
Checks your mailboxes for unread mail. A mail reading program (MUA) can be
executed with a left mouse click on the mail monitor panel button, and
a mail notify (play a sound) program such as esdplay or artsplay can be
executed whenever the new mail count increases.  The mail panel envelope
decal may also be clicked to force an immediate mail check at any time.

GKrellM is capable of checking mail from local mailbox types mbox, MH, and
maildir, and from remote mailbox types POP3 and IMAP.

POP3 and IMAP checking can use non-standard port numbers and password
authentication protocols APOP (for POP3 only) or CRAM-MD5.  If supported
by the mail server, emote checking may be done over an SSL connection if
the "Use SSL" option is selected.

Before internal POP3 and IMAP checking was added, an external mail
fetch/check program could be set up to be executed periodically to
download or check remote POP3 or IMAP mail.  This method is still
available and must be used if you want GKrellM to be able to
download remote mail to local mailboxes because the builtin checking
functions cannot download.


Battery Monitor
--------------------------
This meter will be available if a battery exists and will show battery
percentage life remaining.  A decal indicates if AC line is connected
or if the battery is in use.  If the data is available, time remaining
may be displayed as well as the percentage battery level. If the time
remaining is not available or is inaccurate, the Estimate Time option
may be selected to display a battery time to run or time to charge which
is calculated based on the current battery percent level, user supplied
typical battery times, and a default linear extrapolation model.
For charging, an exponential charge model may be selected.

A battery low level warning and alarm alert may be set.  If battery time
is not available from the OS and the estimate time mode is not set, the
alert units will be battery percent level.  Otherwise the alert units will
be battery time left in minutes.  If OS battery time is not available and the
estimate time mode is set when the alert is created, the alert will have
units of time left in minutes and the alert will automatically be destroyed
if the estimate time option is subsequently turned off.

If the OS reports multiple batteries, the alert will be a master alert
which is duplicated for each battery.

CPU/Motherboard Sensors - Temperature, Voltages, and Fan RPM
------------------------------------------------------------
Linux:
-----
Sensor monitoring requires that either lm_sensors modules are
installed in your running kernel, that you run a kernel >= 2.6 with sysfs
sensors configured, or, for i386 architectures, that you have the mbmon
daemon running when gkrellm is started (as long as mbmon supports reporting
sensor values for your motherboard).

For lm_sensors to be used, gkrellm must be compiled with libsensors support.
It will be if the libsensors development package is installed when gkrellm
is compiled.  Using libsensors is the preferred interface on Linux since it is
the only interface that will be up to date on supporting correct voltage
scaling factors and offsets for recent sensor chips. 

If the mbmon daemon is used, it must be started before gkrellm like so:

    mbmon -r -P port-number

where the given "port-number" must be configured to match in the gkrellm
Sensors->Options config.  If you have mbmon installed from a distribution
package, you can probably easily set up for mbmon to be started at boot.
With Debian, for example, you would edit the file /etc/default/mbmon
to set:

	START_MBMON=1

and you would need to set in the gkrellm Sensors->Option config the
mbmon port to be "411" to match the default in the /etc/default/mbmon
file.

Sensor temperatures can also be read from /proc/acpi/thermal_zone,
/proc/acpi/thermal, /proc/acpi/ibm. the PowerMac Windfarm /sysfs
interface, and PowerMac PMU /sysfs based sensors.

When using lm_sensors, libsensors will be used if available, but if
libsensors is not linked into the program, the sensor data will be
read directly from the /sysfs or /proc file systems.  If running a newer
Linux kernel sensor module not yet supported by libsensors and libsensors
is linked, there will also be an automatic  fallback to using /sysfs as
long as libsensors doesn't detect any sensors.  But if it does detect some
sensors which does not include the new sensors you need, you can force
getting /sysfs sensor data either by running:

    gkrellm --without-libsensors

or by rebuilding with:

    make without-libsensors=yes


Disk temperatures may also be monitored if you have the hddtemp daemon
running when gkrellm is started.  Gkrellm uses the default hddtemp port
of 7634.  Like mbmon, hddtemp is best started in a boot script to guarantee
it will be running when gkrellm is started.


Nvidia graphics card GPU temperatures may also be monitored if
the nvidia-settings command is installed and your Nvidia card supports
the temperature reporting.  If nvidia-settings is not installed or does
not report temperatures for your card, an option for using the nvclock
program will appear in the Sensors config.  Nvclock use is not
automatically enabled as is nvidia-settings because nvclock can add
seconds of gkrellm startup time when used on a NVIDIA GPU chipset it
does not support.  GKrellM must be restarted to recognize changes for
the nvclock option.

Windows
-------
Requires on of:
 - MBM: http://mbm.livewiredev.com/
 - SpeedFan: http://www.almico.com/speedfan.php

FreeBSD
------------------
Builtin sensor reporting is available for some sensor chips.
FreeBSD systems can also read sensor data from the mbmon daemon as described
in the Linux section above.

NetBSD
------------------
Builtin sensor reporting is available for some sensor chips.
NetBSD uses the envsys(4) interface and sensors reading is automatically
enabled if you have either a lm(4) or viaenv(4) chip configured in your kernel.

General Setup:
--------------
Temperature and fan sensor displays may be optionally located on the CPU or
Proc panels to save some vertical space while voltages are always displayed
on their own panel.  If you set up to monitor both a temperature and a fan
on a single CPU or Proc panel, they can be displayed optionally as an
alternating single display or as separate displays.  If separate, the fan
display will replace the panel label.  The configuration for this is under
the CPU and Proc config pages.

If not using libsensors, in the Setup page for the Sensors config enter
any correction factors and offsets for each of the sensors you are monitoring
(see below and lm_sensor documentation).  For Linux, default values are
automatically provided for many sensor chips.

But if using libsenors, it is not possible to enter correction factors and
offsets on the Sensors config page because libsensors configuration is
done in the /etc/sensors.conf file.  To get sensor debug output and to find
out the sensor data source, run:

    gkrellm -d 0x80

Note for NetBSD users: 
The current implementation of the sensor reading under NetBSD opens
/dev/sysmon and never closes it. Since that device does not support
concurrent accesses, you won't be able to run other apps such as
envstat(8) while GKrellM is running.  This might change if this happens
to be an issue.
The reasons for this choice are a) efficiency (though it might be possible
to open/close /dev/sysmon each time a reading is needed without major
performance issue) and b) as of october 2001, there's a bug in the
envsys(4) driver which sometimes causes deadlocks when processes try to
access simultaneously /dev/sysmon  (see NetBSD PR#14368). A (quick and
dirty) workaround for this is to monopolize the driver :)


CPU/Motherboard Temperatures
----------------------------
Most modern motherboards will not require setting temperature correction
factors and offsets other than the defaults.  However, for lm_sensors it
is necessary to have a correct "set sensor" line in /etc/sensors.conf
if the temperature sensor type is other than the default thermistor.
If using Linux sysfs sensors, this sensor type is set by writing to
a sysfs file.  For example, you might at boot set a sysfs temperature sensor
type with:

    echo "2" > /sys/bus/i2c/devices/0-0290/sensor2

On the other hand, some older motherboards may need temperature calibration
by setting a correction factor and offset for each temperature sensor
because of factors such as variations in physical thermistor contact
with the CPU.  Unfortunately, this calibration may not be practical or
physically possible because it requires that somehow you can get a real
CPU temperature reading.  So, the calibration discussion which follows
should probably be considered an academic exercise that might give you
some good (or bad) ideas.  If you have a recent motherboard, skip the
following.

Anyway, to do this calibration, take two real CPU temperature readings
corresponding to two sensor reported readings.   To get the real
readings, you can trust that your motherboard manufacturer has done
this calibration and is reporting accurate temperatures in the bios,
or you can put a temperature probe directly on your CPU case (and this
is where things get impractical).

Here is a hypothetical CPU calibration procedure.  Make sure GKrellM is
configured with default factors of 1.0 and offsets of 0 and is reporting
temperatures in centigrade:

    1) Power on the machine and read a real temperature T1 from the bios or
       a temperature probe.  If reading from the bios, proceed with booting
       the OS.  Now record a sensor temperature S1 as reported by GKrellM.
    2) Change the room temperature environment (turn off your AC or change
       computer fan exhaust speed).  Now repeat step 1, this time recording
       a real temperature T2 and GKrellM reported sensor temperature S2.
    3) Now you can calculate the correction factor and offset you need
       to enter into the Sensor configuration tab:
           From:
                   s - S1     t - T1
                   ------  =  ------
                  S2 - S1    T2 - T1

                                 T2 - T1     S2*T1 - S1*T2
                        t  = s * -------  +  -------------
                                 S2 - S1         S2 - S1

            So:
                          T2 - T1                S2*T1 - S1*T2
                factor =  -------      offset =  -------------
                          S2 - S1                   S2 - S1


Voltage Sensor Corrections
--------------------------
You need to read this section only if you think the default voltage correction
factors and offsets are incorrect.  For Linux and lm_sensors and sysfs sensors
this would be if GKrellM does not know about your particular sensor chip.
For MBM/SpeedFan with Windows, the default values should be correct.

Motherboard voltage measurements are made by a variety of sensor
chips which are capable of measuring a small positive voltage.
GKrellM can display these voltage values and can apply a correction
factor, offset, and for the negative voltages of some chips (lm80), a
level shifting reference voltage to the displayed voltage.  There are
four cases to consider:

  1) Low valued positive voltages may be directly connected to the input
  pins of the sensor chip and therefore need no correction.  For these,
  the correction factor should be 1.0 and the offset should be 0.

  2) Higher valued positive voltages will be connected to the input pins
  of the sensor chip through a 2 resistor attenuation circuit.  For these,
  the correction factor will be a ratio of the resistor values and the
  offset will be 0.

  3) Negative voltages will be connected to the input pins of the sensor
  through a 2 resistor attenuation circuit with one of the resistors
  connected to a positive voltage to effect a voltage level shift.
  For these (lm80), the correction factor and offset will be ratios of the
  resistor values, and a reference voltage must be used.

  4) Some sensor chips (w83782, lm78) are designed to handle negative inputs
  without requiring an input resistor connected to a voltage reference.
  For these, there will be a correction factor and a possible offset.

For cases 2 and 3, the sensor chip input network looks like:

    Vs o----/\/\/---o-------------o Vin
             R1     |
                    o--/\/\--o Vref
                        R2
where,
    Vs   is the motherboard voltage under measurement
    Vin  is the voltage at the input pin of the sensor chip and therefore is
         the voltage reading that will need correction.
    Vref is a level shifting voltage reference.  For case 2, Vref is ground
         or zero.  For case 3, Vref will be one of the positive motherboard
         voltages.

The problem then is to compute correction factors and offsets as a function
of R1 and R2 so that GKrellM can display a computed motherboard voltage Vs
as a function of a measured voltage Vin.

Since sensor chip input pins are high impedance, current into the pins may
be assumed to be zero.  In that case, the current through R1 equals current
through R2, and we have:

    (Vs - Vin)/R1 = (Vin - Vref)/R2

Solving for Vs as a function of Vin:

    Vs = Vin * (1 + R1/R2)  -  (R1/R2) * Vref

So, the correction factor is:  1 + R1/R2
    the correction offset is:  - (R1/R2)
    Vref is specified in the config separately from the offset (for
    chips that need it).

Fortunately there seems to be a standard set of resistor values used
for the various sensor chips which are documented in the lm_sensor
documentation.  The GKrellM sensor corrections are similar to the compute
lines you find with lm_sensors, with the difference that lm_sensors has an
expression evaluator which does not require that compute lines be simplified
to the single factor and offset required by GKrellM.  But you can easily
calculate the factor and offset.  For example, this lm_sensor compute line
for a case 2 voltage:

    compute in3 ((6.8/10)+1)*@ ,  @/((6.8/10)+1)

yields a correction factor of ((6.8/10)+1) = 1.68
and an offset of zero.

Note that the second compute line expression is not relevant in GKrellM
because there is never any need to invert the voltage reading calculation.
Also, the compute line '@' symbol represents the Vin voltage.

A more complicated compute line for a case 3 voltage:

    compute in5 (160/35.7)*(@ - in0) + @, ...

can be rewritten:

    compute in5 (1 + 160/35.7)*@ - (160/35.7)*in0, ...

so the correction factor is  (1 + 160/35.7) = 5.48
and the correction offset is -(160/35.7) = -4.48
and the voltage reference Vref is in0

Here is a table of correction factors and offsets based on some typical
compute line entries from /etc/sensors.conf:

       Compute line                     Factor  Offset  Vref
       -----------------------------------------------------
lm80   in0 (24/14.7 + 1) * @            2.633     0       -
       in2 (22.1/30 + 1) * @            1.737     0       -
       in3 (2.8/1.9) * @                1.474     0       -
       in4 (160/30.1 + 1) * @           6.316     0       -
       in5 (160/35.7)*(@ - in0) + @     5.482    -4.482  in0
       in6 (36/16.2)*(@ - in0) + @      3.222    -2.222  in0

LM78   in3 ((6.8/10)+1)*@               1.68      0       -
       in4 ((28/10)+1)*@                3.8       0       -
       in5 -(210/60.4)*@               -3.477     0       -
       in6 -(90.9/60.4)*@              -1.505     0       -

w83782 in5 (5.14 * @) - 14.91           5.14    -14.91    -
       in6 (3.14 * @) -  7.71           3.14     -7.71    -



Command launching
=================
Many monitors can be set up to launch a command when you click on
the monitor label.  When a command is configured for a monitor, its
label is converted into a button which becomes visible when the mouse
enters the panel or meter area of the label.  If the command is a
console command (doesn't have a graphical user interface), then
the command must be run in a terminal window such as xterm, eterm,
or Gnome terminal.  For example running the "top" command would take:

    xterm -e top

You can use the command launching feature to run commands related to
monitoring functions, or you may use it to have a convenient launch
for any command.  Since GKrellM is usually made sticky, you can have
easy access to several frequently used commands from any desktop.
This is intended to be a convenience and a way to maximize utilization
of screen real estate and not a replacement for more full featured
command launching from desktops such as Gnome or KDE or others.
Some launch ideas for some monitors could be:

   calendar: gnomecal, evolution, or ical
        CPU: xterm -e top  or  gps  or  gtop
       inet: gftp  or  xterm -e ftpwho
        net: mozilla, galeon, skipstone,  or  xterm -e slrn -C-
and so on...

Tooltips can be set up for these commands.


Alerts
======
Most monitors can have alerts configured to give warnings and alarms
for data readings which range outside of configurable limits.  Where
useful, a delay of the alert trigger can be configured.  A warning or
alarm consists of an attention grabbing decal appearing and an optional
command being executed.  For most monitors the command may contain the
same substitution variables which are available for display in the
chart or panel label format strings and are documented on configuration
Info pages.  Additionally, the hostname may be embedded in the command
with the $H substitution variable.

If you have festival installed, either a warn or alarm command
could be configured to speak something.  For example a CPU temperature
alert warn command could just speak the current temperature with:

    sh -c "echo warning C P U is at $s degrees | esddsp festival --tts"

Assuming you have esd running.


Installing a Theme for GKrellM
==============================

A theme is a directory containing image files and a gkrellmrc
configuration file.  The theme directory may be installed in
several locations:

	~/.gkrellm2/themes
	/usr/local/share/gkrellm2/themes
	/usr/share/gkrellm2/themes

For compatibility with Gtk themes, a GKrellM theme may also be installed
as:
	~/.themes/THEME_NAME/gkrellm2
	/usr/share/themes/THEME_NAME/gkrellm2

Finally, a theme you simply want to check out can be untarred anywhere
and used by running:

	gkrellm -t path_to_theme

Read the Themes file if you want more information or are interested in
making a new theme for GKrellM.


Plugins
=======

GKrellM tries to load all plugins (shared object files ending in .so)
it finds in your plugin directory ~/.gkrellm2/plugins.  The directories
/usr/local/lib/gkrellm2/plugins and /usr/lib/gkrellm2/plugins are
also searched for plugins to install.

Some plugins may be available only as source files and they will
have to be compiled before installation.  There should be instructions
for doing this with each plugin that comes in source form.

If you are interested in writing a plugin, go to the Plugins page
at https://gkrellm.srcbox.net and there you will find a Plugin programmers
reference and Plugins-changelog.


Client/Server
=============
When gkrellm connects to a gkrellmd server all builtin monitors collect
their data from the server.  However, the gkrellm process is running
on the local machine, so any enabled plugins will run in the local
context (Flynn is an example exception to this since it derives its data
from the builtin CPU monitor).  Also, any command launching will run
commands on the local machine.
