> ## 1 Embedded Solaris

> This chapter describes the OS specific parts of OTP which relate to Solaris.

> ### 1.1 Memory Usage

> Solaris takes about 17 Mbyte of RAM on a system with 64 Mbyte of total RAM. This leaves about 47 Mbyte for the applications. If the system utilizes swapping, these figures cannot be improved because unnecessary daemon processes are swapped out. However, if swapping is disabled, or if the swap space is of limited resource in the system, it becomes necessary to kill off unnecessary daemon processes.

> ### 1.2 Disk Space Usage

> The disk space required by Solaris can be minimized by using the Core User support installation. It requires about 80 Mbyte of disk space. This installs only the minimum software required to boot and run Solaris. The disk space can be further reduced by deleting unnecessary individual files. However, unless disk space is a critical resource the effort required and the risks involved may not be justified.

> ### 1.3 Installation

> This section is about installing an embedded system. The following topics are considered,

> - Creation of user and installation directory,
> - Installation of embedded system,
> - Configuration for automatic start at reboot,
> - Making a hardware watchdog available,
> - Changing permission for reboot,
> - Patches,
> - Configuration of the OS_Mon application.

> Several of the procedures described below require expert knowledge of the Solaris 2 operating system. For most of them super user privilege is needed.

> #### 1.3.1 Creation of User and Installation Directory

> It is recommended that the Embedded Environment is run by an ordinary user, i.e. a user who does not have super user privileges.

> Throughout this section we assume that the user name is `otpuser`, and that the home directory of that user is,

>        /export/home/otpuser

> Furthermore, we assume that in the home directory of `otpuser`, there is a directory named `otp`, the full path of which is,

>        /export/home/otpuser/otp

> This directory is the installation directory of the Embedded Environment.

> #### 1.3.2 Installation of an Embedded System

> The procedure for installation of an embedded system does not differ from that of an ordinary system (see the Installation Guide), except for the following:

> - the (compressed) tape archive file should be extracted in the installation directory as defined above, and,
> - there is no need to link the start script to a standard directory like `/usr/local/bin`.

> #### 1.3.3 Configuration for Automatic Start at Boot

> A true embedded system has to start when the system boots. This section accounts for the necessary configurations needed to achieve that.

> The embedded system and all the applications will start automatically if the script file shown below is added to the `/etc/rc3.d` directory. The file must be owned and readable by `root`, and its name cannot be arbitrarily assigned. The following name is recommended,

>        S75otp.system

> For further details on initialization (and termination) scripts, and naming thereof, see the Solaris documentation.

>     #!/bin/sh
>     #
>     #  File name:  S75otp.system
>     #  Purpose:    Automatically starts Erlang and applications when the
>     #              system starts
>     #  Author:     janne@erlang.ericsson.se
>     #  Resides in: /etc/rc3.d
>     #

>     if [ ! -d /usr/bin ]
>     then                    # /usr not mounted
>             exit
>     fi

>     killproc() {            # kill the named process(es)
>             pid=`/usr/bin/ps -e |
>                  /usr/bin/grep -w $1 |
>                  /usr/bin/sed -e 's/^  *//' -e 's/ .*//'`
>             [ "$pid" != "" ] && kill $pid
>     }

>     # Start/stop processes required for Erlang

>     case "$1" in
>     'start')
>             # Start the Erlang emulator
>             #
>             su - otpuser -c "/export/home/otpuser/otp/bin/start" &
>             ;;
>     'stop')
>             killproc beam
>             ;;
>     *)
>             echo "Usage: $0 { start | stop }"
>             ;;
>     esac

> The file `/export/home/otpuser/otp/bin/start` referred to in the above script, is precisely the script `start` described in the section Starting Erlang below. The script variable `OTP_ROOT` in that `start` script corresponds to the example path

>        /export/home/otpuser/otp

> used in this section. The `start` script should be edited accordingly.

> Use of the `killproc` procedure in the above script could be combined with a call to `erl_call`, e.g.

>        $SOME_PATH/erl_call -n Node init stop

> In order to take Erlang down gracefully see the `erl_call(1)` reference manual page for further details on the use of `erl_call`. That however requires that Erlang runs as a distributed node which is not always the case.

> The `killproc` procedure should not be removed: the purpose is here to move from run level 3 (multi-user mode with networking resources) to run level 2 (multi-user mode without such resources), in which Erlang should not run.

> #### 1.3.4 Hardware Watchdog

> For Solaris running on VME boards from Force Computers, there is a possibility to activate the onboard hardware watchdog, provided a VME bus driver is added to the operating system (see also Installation Problems below).

> See also the `heart(3)` reference manual page in Kernel.

> #### 1.3.5 Changing Permissions for Reboot

> If the `HEART_COMMAND` environment variable is to be set in the `start` script in the section, Starting Erlang, and if the value shall be set to the path of the Solaris `reboot` command, i.e.

>        HEART_COMMAND=/usr/sbin/reboot

> the ownership and file permissions for `/usr/sbin/reboot` must be changed as follows,

>        chown 0 /usr/sbin/reboot
>             chmod 4755 /usr/sbin/reboot

> See also the `heart(3)` reference manual page in Kernel.

> #### 1.3.6 The TERM Environment Variable

> When the Erlang runtime system is automatically started from the `S75otp.system` script the `TERM` environment variable has to be set. The following is a minimal setting,

>        TERM=sun

> which should be added to the `start` script described in the section.

> #### 1.3.7 Patches

> For proper functioning of flushing file system data to disk on Solaris 2.5.1, the version specific patch with number 103640-02 must be added to the operating system. There may be other patches needed, see the release README file `<ERL_INSTALL_DIR>/README`.

> #### 1.3.8 Installation of Module os_sup in Application OS_Mon

> The following four installation procedures require super user privilege.

> ##### 1.3.8.1 Installation

> 1. Make a copy the Solaris standard configuration file for syslogd.
>    - Make a copy the Solaris standard configuration file for syslogd. This file is usually named `syslog.conf` and found in the `/etc` directory.
>    - The file name of the copy must be `syslog.conf.ORIG` but the directory location is optional. Usually it is `/etc`.
>      A simple way to do this is to issue the command

>          cp /etc/syslog.conf /etc/syslog.conf.ORIG

> 2. Make an Erlang specific configuration file for syslogd.
>    - Make an edited copy of the back-up copy previously made.
>    - The file name must be `syslog.conf.OTP` and the path must be the same as the back-up copy.
>    - The format of the configuration file is found in the man page for `syslog.conf(5)`, by issuing the command `man syslog.conf`.
>    - Usually a line is added which should state:
>      - which types of information that will be supervised by Erlang,
>      - the name of the file (actually a named pipe) that should receive the information.
>    - If e.g. only information originating from the unix-kernel should be supervised, the line should begin with `kern.LEVEL` (for the possible values of `LEVEL` see `syslog.conf(5)`).
>    - After at least one tab-character, the line added should contain the full name of the named pipe where syslogd writes its information. The path must be the same as for the `syslog.conf.ORIG` and `syslog.conf.OTP` files. The file name must be `syslog.otp`.
>    - If the directory for the `syslog.conf.ORIG` and `syslog.conf.OTP` files is `/etc` the line in `syslog.conf.OTP` will look like:

>          kern.LEVEL         /etc/syslog.otp

> 3. Check the file privileges of the configuration files.
>    - The configuration files should have `rw-r--r--` file privileges and be owned by root.
>    - A simple way to do this is to issue the commands

>          chmod 644 /etc/syslog.conf
>          chmod 644 /etc/syslog.conf.ORIG
>          chmod 644 /etc/syslog.conf.OTP

>    - Note: If the `syslog.conf.ORIG` and `syslog.conf.OTP` files are not in the `/etc` directory, the file path in the second and third command must be modified.
> 4. Modify file privileges and ownership of the mod_syslog utility.
>    - The file privileges and ownership of the `mod_syslog` utility must be modified.
>    - The full name of the binary executable file is derived from the position of the `os_mon` application if the file system by adding `/priv/bin/mod_syslog`. The generic full name of the binary executable file is thus

>          <OTP_ROOT>/lib/os_mon-<REV>/priv/bin/mod_syslog

>      Example: If the path to the otp-root is `/usr/otp`, thus the path to the `os_mon` application is `/usr/otp/lib/os_mon-1.0` (assuming revision 1.0) and the full name of the binary executable file is `/usr/otp/lib/os_mon-1.0/priv/bin/mod_syslog`.
>    - The binary executable file must be owned by root, have `rwsr-xr-x` file privileges, in particular the setuid bit of user must be set.
>    - A simple way to do this is to issue the commands

>          cd <OTP_ROOT>/lib/os_mon-<REV>/priv/bin/mod_syslog
>          chmod 4755 mod_syslog
>          chown root mod_syslog

> ##### 1.3.8.2 Testing the Application Configuration File

> The following procedure does not require root privilege.

> - Ensure that the configuration parameters for the `os_sup` module in the `os_mon` application are correct.
> - Browse the application configuration file (do not edit it). The full name of the application configuration file is derived from the position of the OS_Mon application if the file system by adding `/ebin/os_mon.app`.
>   The generic full name of the file is thus

>       <OTP_ROOT>/lib/os_mon-<REV>/ebin/os_mon.app.

>   Example: If the path to the otp-root is `/usr/otp`, thus the path to the `os_mon` application is `/usr/otp/lib/os_mon-1.0` (assuming revision 1.0) and the full name of the binary executable file is `/usr/otp/lib/os_mon-1.0/ebin/os_mon.app`.
> - Ensure that the following configuration parameters are bound to the correct values.

> Parameter | Function | Standard value
> start_os_sup | Specifies if os_sup will be started or not. | `true` for the first instance on the hardware; `false` for the other instances.
> os_sup_own | The directory for (1)the back-up copy, (2) the Erlang specific configuration file for syslogd. | `"/etc"`
> os_sup_syslogconf | The full name for the Solaris standard configuration file for syslogd | `"/etc/syslog.conf"`
> error_tag | The tag for the messages that are sent to the error logger in the Erlang runtime system. | `std_error`
> Configuration Parameters

> If the values listed in the `os_mon.app` do not suit your needs, you should `not` edit that file. Instead you should override values in a system configuration file, the full pathname of which is given on the command line to `erl`.

> Example: The following is an example of the contents of an application configuration file.

>          [{os_mon, [{start_os_sup, true}, {os_sup_own, "/etc"},
>               {os_sup_syslogconf, "/etc/syslog.conf"}, {os_sup_errortag, std_error}]}].

> ##### 1.3.8.3 Related Documents

> See also the `os_mon(3)`, `application(3)` and `erl(1)` reference manual pages.

> #### 1.3.9 Installation Problems

> The hardware watchdog timer which is controlled by the `heart` port program requires the `FORCEvme` package, which contains the VME bus driver, to be installed. This driver, however, may clash with the Sun `mcp` driver and cause the system to completely refuse to boot. To cure this problem, the following lines should be added to `/etc/system`:

> - `exclude: drv/mcp`
> - `exclude: drv/mcpzsa`
> - `exclude: drv/mcpp`

> | It is recommended that these lines be added to avoid the clash described, which may make it completely impossible to boot the system.

> ### 1.4 Starting Erlang

> This section describes how an embedded system is started. There are four programs involved, and they all normally reside in the directory `<ERL_INSTALL_DIR>/bin`. The only exception is the program `start`, which may be located anywhere, and also is the only program that must be modified by the user.

> In an embedded system there usually is no interactive shell. However, it is possible for an operator to attach to the Erlang system by giving the command `to_erl`. He is then connected to the Erlang shell, and may give ordinary Erlang commands. All interaction with the system through this shell is logged in a special directory.

> Basically, the procedure is as follows. The program `start` is called when the machine is started. It calls `run_erl`, which sets things up so the operator can attach to the system. It calls `start_erl` which calls the correct version of `erlexec` (which is located in `<ERL_INSTALL_DIR>/erts-EVsn/bin`) with the correct `boot` and `config` files.

> ### 1.5 Programs

> #### 1.5.1 start

> This program is called when the machine is started. It may be modified or re-written to suit a special system. By default, it must be called `start` and reside in `<ERL_INSTALL_DIR>/bin`. Another start program can be used, by using the configuration parameter `start_prg` in the application `sasl`.

> The start program must call `run_erl` as shown below. It must also take an optional parameter which defaults to `<ERL_INSTALL_DIR>/releases/start_erl.data`.

> This program should set static parameters and environment variables such as `-sname Name` and `HEART_COMMAND` to reboot the machine.

> The `<RELDIR>` directory is where new release packets are installed, and where the release handler keeps information about releases. See `release_handler(3)` in the application `sasl` for further information.

> The following script illustrates the default behaviour of the program.

>     #!/bin/sh
>     # Usage: start [DataFile]
>     #
>     ROOTDIR=/usr/local/otp

>     if [ -z "$RELDIR" ]
>     then
>        RELDIR=$ROOTDIR/releases
>     fi

>     START_ERL_DATA=${1:-$RELDIR/start_erl.data}

>     $ROOTDIR/bin/run_erl /tmp/ $ROOTDIR/log "exec $ROOTDIR/bin/start_erl \
>                          $ROOTDIR $RELDIR $START_ERL_DATA" > /dev/null 2>&1 &

> The following script illustrates a modification where the node is given the name `cp1`, and the environment variables `HEART_COMMAND` and `TERM` have been added to the above script.

>     #!/bin/sh
>     # Usage: start [DataFile]
>     #
>     HEART_COMMAND=/usr/sbin/reboot
>     TERM=sun
>     export HEART_COMMAND TERM

>     ROOTDIR=/usr/local/otp

>     if [ -z "$RELDIR" ]
>     then
>        RELDIR=$ROOTDIR/releases
>     fi

>     START_ERL_DATA=${1:-$RELDIR/start_erl.data}

>     $ROOTDIR/bin/run_erl /tmp/ $ROOTDIR/log "exec $ROOTDIR/bin/start_erl \
>           $ROOTDIR $RELDIR $START_ERL_DATA -heart -sname cp1" > /dev/null 2>&1 &

> If a diskless and/or read-only client node is about to start the `start_erl.data` file is located in the client directory at the master node. Thus, the `START_ERL_DATA` line should look like:

>     CLIENTDIR=$ROOTDIR/clients/clientname
>     START_ERL_DATA=${1:-$CLIENTDIR/bin/start_erl.data}

> #### 1.5.2 run_erl

> This program is used to start the emulator, but you will not be connected to the shell. `to_erl` is used to connect to the Erlang shell.

>     Usage: run_erl pipe_dir/ log_dir "exec command [parameters ...]"

> Where `pipe_dir/` should be `/tmp/` (`to_erl` uses this name by default) and `log_dir` is where the log files are written. `command [parameters]` is executed, and everything written to stdin and stdout is logged in the `log_dir`.

> In the `log_dir`, log files are written. Each logfile has a name of the form: `erlang.log.N` where N is a generation number, ranging from 1 to 5. Each logfile holds up to 100kB text. As time goes by the following logfiles will be found in the logfile directory

>     erlang.log.1
>     erlang.log.1, erlang.log.2
>     erlang.log.1, erlang.log.2, erlang.log.3
>     erlang.log.1, erlang.log.2, erlang.log.3, erlang.log.4
>     erlang.log.2, erlang.log.3, erlang.log.4, erlang.log.5
>     erlang.log.3, erlang.log.4, erlang.log.5, erlang.log.1
>     ...

> with the most recent logfile being the right most in each row of the above list. That is, the most recent file is the one with the highest number, or if there are already four files, the one before the skip.

> When a logfile is opened (for appending or created) a time stamp is written to the file. If nothing has been written to the log files for 15 minutes, a record is inserted that says that we're still alive.

> #### 1.5.3 to_erl

> This program is used to attach to a running Erlang runtime system, started with `run_erl`.

>     Usage: to_erl [pipe_name | pipe_dir]

> Where `pipe_name` defaults to `/tmp/erlang.pipe.N`.

> To disconnect from the shell without exiting the Erlang system, type `Ctrl-D`.

> #### 1.5.4 start_erl

> This program starts the Erlang emulator with parameters `-boot` and `-config` set. It reads data about where these files are located from a file called `start_erl.data` which is located in the `<RELDIR>`. Each new release introduces a new data file. This file is automatically generated by the release handler in Erlang.

> The following script illustrates the behaviour of the program.

>     #!/bin/sh
>     #
>     # This program is called by run_erl.  It starts
>     # the Erlang emulator and sets -boot and -config parameters.
>     # It should only be used at an embedded target system.
>     #
>     # Usage: start_erl RootDir RelDir DataFile [ErlFlags ...]
>     #
>     ROOTDIR=$1
>     shift
>     RELDIR=$1
>     shift
>     DataFile=$1
>     shift

>     ERTS_VSN=`awk '{print $1}' $DataFile`
>     VSN=`awk '{print $2}' $DataFile`

>     BINDIR=$ROOTDIR/erts-$ERTS_VSN/bin
>     EMU=beam
>     PROGNAME=`echo $0 | sed 's/.*\///'`
>     export EMU
>     export ROOTDIR
>     export BINDIR
>     export PROGNAME
>     export RELDIR

>     exec $BINDIR/erlexec -boot $RELDIR/$VSN/start -config $RELDIR/$VSN/sys $*

> If a diskless and/or read-only client node with the `sasl` configuration parameter `static_emulator` set to `true` is about to start the `-boot` and `-config` flags must be changed. As such a client cannot read a new `start_erl.data` file (the file is not possible to change dynamically) the boot and config files are always fetched from the same place (but with new contents if a new release has been installed). The `release_handler` copies this files to the `bin` directory in the client directory at the master nodes whenever a new release is made permanent.

> Assuming the same `CLIENTDIR` as above the last line should look like:

>     exec $BINDIR/erlexec -boot $CLIENTDIR/bin/start \
>          -config $CLIENTDIR/bin/sys $*

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