frontend.md

title: The 66 Suite: frontend author: Eric Vidal eric@obarun.org

66

Software

obarun.org

The frontend service file

The s6 programs use different files. It is quite complex to understand and manage the relationship between all those files. If you're interested in the details you should read the documentation for the s6 servicedir and also about classic and module services. The frontend service file of 66 program allows you to deal with all these different services in a centralized manner and in one single location.

By default 66 program expects to find service files in %%service_system%% and %%service_adm%% for root user. For regular users, $HOME/%%service_user%% will take priority over the previous ones. Although this can be changed at compile time by passing the --with-system-service=DIR, --with-sysadmin-service=DIR and --with-user-service=DIRoption to ./configure.

The frontend service file has a format of INI with a specific syntax on the key field. The name of the file usually corresponds to the name of the daemon and does not have any extension or prefix.

The file is made of sections which can contain one or more key value pairs where the key name can contain special characters like - (hyphen) or _ (low line) except the character @ (commercial at) which is reserved.

You can find a prototype with all valid section and all valid key=value pair at the end of this document.

File names examples

    %%service_system%%/dhcpcd
    %%service_system%%/very_long_name_which_make_no_sense

File content example

    [main]
    @type = classic
    @description = "ntpd daemon"
    @version = 0.1.0
    @user = ( root )

    [start]
    @execute = (
        foreground { mkdir -p  -m 0755 ${RUNDIR} }
        execl-cmdline -s { ntpd ${CMD_ARGS} }
    )

    [environment]
    RUNDIR=!/run/openntpd
    CMD_ARGS=!-d -s

The parser will not accept an empty value. If a key is set then the value can not be empty. Comments are allowed using the number sign #. Empty lines are also allowed.

Key names are case sensitive and can not be modified. Most names should be specific enough to avoid confusion.

The [main] section must be declared first.

Sections

All sections need to be declared with the name written between square brackets [] and must be of lowercase letters only. This means that special characters, uppercase letters and numbers are not allowed in the name of a section.

The frontend service file allows the following section names:

• main(frontend.html#Section: [main])
• start(frontend.html#Section: [start])
• stop(frontend.html#Section: [stop])
• logger(frontend.html#Section: [logger])
• environment(frontend.html#Section: [environment])
• regex(frontend.html#Section: [regex])

Although a section can be mandatory not all of its key fields must be necessarily so.

---

Syntax legend

The value of a key is parsed in a specific format depending on the key. The following is a break down of how to write these syntaxes:

• inline: An inline value. Must be on the same line with its corresponding key.

  • Valid syntax:

    @type = classic
    
    @type=classic

  • (!) Invalid syntax:

    @type=
    classic

  ---

• quotes: A value between double-quotes. Must be on the same line with its corresponding key.

  • Valid syntax:

    @description = "some awesome description"
    
    @description="some awesome description"

  • (!) Invalid syntax:

    @description=
    "some awesome description"
    
    @description = "line break inside a double-quote
    is not allowed"

  ---

• brackets: Multiple values between parentheses (). Values need to be separated with a space. A line break can be used instead.

  • Valid syntax:

    @depends = ( fooA fooB fooC )
    
    @depends=(fooA fooB fooC)
    
    @depends=(
    fooA
    fooB
    fooC
    )
    
    @depends=
    (
    fooA
    fooB
    fooC
    )

  • (!) Invalid syntax:

    @depends = (fooAfooBfooC)

  ---

• uint: A positive whole number. Must be on the same line with its corresponding key.

  • Valid syntax:

    @notify = 3
    
    @notify=3

  • (!) Invalid syntax:

    @notify=
    3

  ---

• path: An absolute path beginning with a forward slash /. Must be on the same line with its corresponding key.

  • Valid syntax:

    @destination = /etc/66
    
    @destination=/etc/66

  • (!) Invalid syntax:

    @destination=/a/very/
    long/path

  ---

• pair: same as inline.

  • Valid syntax:

    MYKEY = MYVALUE
    
    anotherkey=anothervalue
    
    anotherkey=where_value=/can_contain/equal/Character

  • (!) Invalid syntax:

    MYKEY=
    MYVALUE

  ---

• colon: A value between double colons followed by a pair syntax. Must be one by line.

  • Valid syntax:

    ::key=value
    
    :filename:key=value

  • (!) Invalid syntax:

    ::MYKEY=
    MYVALUE
    
    ::
    MYKEY=MYVALUE
    
    ::key=value :filename:anotherkey=anothervalue

• simple-colon: A values separated by a colon. Must be on the same line with its corresponding key.

  • Valid syntax:

    @runas = 1000:19

  • (!) Invalid syntax:

    @runas = 1000:
    19

---

Section: [main]

This section is mandatory. (!)

Valid key names:

• @type

  Declare the type of the service.

  mandatory : yes (!)

  syntax : inline

  valid values :

  • classic : declares the service as a classic service.
  • oneshot : declares the service as a oneshot service.
  • module : declares the service as a module service.

  ---

• @version

  Version number of the service.

  mandatory : yes (!)

  syntax : inline

  valid values :

  • Any valid version number under the form digit.digit.digit.

    For example, the following is valid:

        @version = 0.1.0

    where:

        @version = 0.1.0.1
        @version = 0.1
        @version = 0.1.rc1

    is not.

  ---

• @description

  A short description of the service.

  mandatory : yes (!)

  syntax : quote

  valid values :

  • Anything you want.

  ---

• @user

  Declare the permissions of the service.

  mandatory : yes (!)

  syntax : bracket

  valid values :

  • Any valid user of the system. If you don't know in advance the name of the user who will deal with the service, you can use the term user. In that case every user of the system will be able to deal with the service.

  (!) Be aware that root is not automatically added. If you don't declare root in this field, you will not be able to use the service even with root privileges.

  ---

• @depends

  Declare dependencies of the service.

  mandatory : no

  syntax : bracket

  valid values :

  • The name of any valid service.

  The order is of importance (!). If fooA depends on fooB and fooB depends on fooC the order needs to be:

      @depends=(fooA fooB fooC )

  It is unnecessary to manually define chained sets of dependencies, see 66.

  A service can be commented out by placing the number sign # at the begin of the name like this:

      @depends = ( fooA #fooB fooC )

  ---

• @requiredby

  Declare required-by dependencies of the service.

  mandatory : no

  syntax : bracket

  valid values :

  • The name of any valid service.

  The order is of importance (!). If fooA is required by fooB and fooB is required by fooC the order needs to be:

      @requiredby=(fooA fooB fooC )

  It is unnecessary to manually define chained sets of dependencies, see 66.

  A service can be commented out by placing the number sign # at the begin of the name like this:

      @depends = ( fooA #fooB fooC )

  ---

• @optsdepends

  Declare optional dependencies of the service.

  mandatory : no

  syntax : bracket

  valid values :

  • The name of any valid service. A service declared as optional dependencies is not mandatory. The parser will look the corresponding service:
    • If enabled, it will warn the user and do nothing.
    • If not, it will try to find the corresponding frontend file.
      • If the frontend service file is found, it will enable it.
      • If it is not found, it will warn the user and do nothing.

  The order is important (!). The first service found will be used and the parse process of the field will be stopped. So, you can considere @optsdepends field as: "enable one on this service or none".

  A service can be commented out by placing the number sign # at the begin of the name like this:

      @optsdepends = ( fooA #fooB fooC )

  ---

• @options

  mandatory : no

  syntax : bracket

  valid values :

  • log : automatically create a logger for the service. This is default. The logger will be created even if this options is not specified. If you want to avoid the creation of the logger, prefix the options with an exclamation mark:

        @options = ( !log )

    The behavior of the logger can be configured in the corresponding section—see logger(frontend.html#Section: [logger]).

  ---

• @flags

  mandatory : no

  syntax : bracket

  valid values :

  • down: This will create the file down corresponding to the file down of s6 program.
  • earlier: This set the service as an earlier service meaning starts the service as soon as the scandir is up.

  Once this file was created the default state of the service will be considered down, not up: the service will not automatically be started until it receives a 66 start command. Without this file the default state of the service will be up and started automatically.

  ---

• @notify

  mandatory : no

  syntax : uint

  valid values :

  • Any valid number.

  This will create the file notification-fd. Once this file is created the service supports readiness notification. The value equals the number of the file descriptor that the service writes its readiness notification to. (For instance, it should be 1 if the daemon is s6-ipcserverd run with the -1 option.) When the service reseive signal and this file is present containing a valid descriptor number, 66 command will wait for the notification from the service and broadcast its readiness.

  ---

• @timeout-finish

  Corresponds to the file timeout-finish of s6 program and used by service of type classic.

  mandatory : no

  syntax : uint

  valid values :

  • Any valid number.

  This will create the file timeout-finish. Once this file is created the value will equal the number of milliseconds after which the ./finish script—if it exists—will be killed with a SIGKILL. The default is 0 allowing finish scripts to run forever.

  ---

• @timeout-kill

  Corresponds to the file timeout-kill of s6 program and used by service of type classic.

  mandatory : no

  syntax : uint

  valid values :

  • Any valid number.

  This will create the file timeout-kill. Once this file is created and the value is not 0, then on reception of a stop command—which sends a SIGTERM and a SIGCONT to the service — a timeout of value in milliseconds is set. If the service is still not dead, after value in milliseconds, it will receive a SIGKILL. If the file does not exist, or contains 0, or an invalid value, then the service is never forcibly killed.

  ---

• @timeout-up

  The file is used for type oneshot.

  mandatory : no

  syntax : uint

  valid value :

  • Any valid number.

  This will create the file timeout-up. Once this file is created the value will equal the maximum number of milliseconds that start command will wait for successful completion of the service start. If starting the service takes longer than this value, start command will declare the transition a failure. If the value is 0, which is the default, no timeout is defined and start command will wait for the service to start until the maxdeath is reached.

  ---

• @timeout-down

  The file is used for type oneshot.

  mandatory : no

  syntax : uint

  valid value :

  • Any valid number.

  This will create the file timeout-down. Once this file is created the value will equal the maximum number of milliseconds stop command will wait for successful completion of the service stop. If starting the service takes longer than this value, stop command will declare the transition a failure. If the value is 0, no timeout is defined and stop command will wait for the service to start until the maxdeath is reached. Without this file a value of 3000 (3 seconds) will be used by default.

  ---

• @maxdeath

  Corresponds to the file max-death-tally of s6 program.

  mandatory : no

  syntax : uint

  valid value :

  • Any valid number.

  This will create the file max-death-tally. Once this file was created the value will equal the maximum number of service death events that the supervisor will keep track of. If the service dies more than this number of times, the oldest event will be forgotten and the transition (start or stop) will be declared as failed. Tracking death events is useful, for example, when throttling service restarts. The value cannot be greater than 4096. Without this file a default of 10 is used.

  ---

• @down-signal

  Corresponds to the file "down-signal" of s6 program.

  mandatory : no

  syntax : uint

  valid value :

  • The name or number of a signal.

  This will create the file down-signal which is used to kill the supervised process when a reload, restart or stop command is used. If the file does not exist SIGTERM will be used by default.

  ---

• @hiercopy

  Verbatim copy directories and files on the fly to the main service destination.

  mandatory : no

  syntax : bracket

  valid values :

  • Any files or directories. It accepts absolute or relative path.

    Note: 66 version must be higher than 0.3.0.1.

• @intree

  mandatory : no

  syntax : inline

  valid values :

  • Any name.

  The service will automatically be activated at the tree name set in the @intree key value.

  Note: If a corresponding seed file exist on your system, its will be used to create and configure the tree.

  ---

---

Section: [start]

This section is mandatory. (!)

Valid key names:

• @build

  mandatory : no

  syntax : inline

  valid value :

  • auto : creates the service script file as execline script. This is the default.

    The corresponding file to start the service will automatically be written in execline format with the @execute key value.

  • custom : creates the service script file making a verbatim copy of the @execute field of the section. Do not forget to set the shebang of the script at @execute key.

  ---

• @runas

  mandatory : no

  syntax : inline,simple-colon

  valid value :

  • Any valid user name set on the system or valid uid:gid number.

      @runas = oblive
  
      @runas = 1000:19
  
      if uid is not specified, the uid of the owner of the process is pick by default
      @runas = :19
  
      if gid is not specified, the gid of the owner of the process is pick by default
      @runas = 1000:
  

  This will pass the privileges of the service to the given user before starting the run script of the service.

  Note: (!) The service needs to be first started with root if you want to hand over priviliges to a user. Only root can pass on privileges. This field has no effect for other use cases.

  ---

• @execute

  mandatory : yes (!)

  syntax : bracket

  valid value :

  • The command to execute when starting the service.

  Note: The field will be used as is. No changes will be applied at all. It's the responsability of the author to make sure that the content of this field is correct.

---

Section: [stop]

This section is optional.

This section is exactly the same as start(frontend.html#Section: [start]) and shares the same keys. With the exception that it will handle the stop process of the service.

---

Section: [logger]

This section is optional.

It will only have effects if value log was not prefixed by an exclamation mark to the @options key in the main(frontend.html#Section: [main]) section.

This section extends the @build, @runas, and @execute key fields from start(frontend.html#Section: [start]) and the @timeout-finish and @timeout-kill key fields from main(frontend.html#Section: [main]) . These are also valid keys for logger(frontend.html#Section: [logger]) and behave the same way they do in the other sections but they can not be specified except for the mandatory key @build—see example below. In such case the default behaviour for those key are apply.

Furthermore there are some keys specific to the log.

Valid key names:

• @build, @runas, and @execute — See start(frontend.html#Section: [start])

• @timeout-finish, @timeout-kill — See main(frontend.html#Section: [main])

  ---

• @destination

  mandatory : no

  syntax : path

  valid value :

  • Any valid path on the system.

  The directory where the log file is saved. This directory is automatically created. The current user of the process needs to have sufficient permissions on the destination directory to be able to create it. The default directory is %%system_log%%/service_name for root and $HOME/%%user_log%%/service_name for any user. The default can also be changed at compile-time by passing the --with-system-logpath=DIR option for root and --with-user-logpath=DIR for a user to ./configure.

  ---

• @backup

  mandatory : no

  syntax : uint

  valid value :

  • Any valid number.

  The log directory will keep value files. The next log to be saved will replace the oldest file present. By default 3 files are kept.

  ---

• @maxsize

  mandatory : no

  syntax : uint

  valid value :

  • Any valid number.

  A new log file will be created every time the current one approaches value bytes. By default, filesize is 1000000; it cannot be set lower than 4096 or higher than 268435455.

  ---

• @timestamp

  mandatory : no

  syntax : inline

  valid value :

  • tai

  The logged line will be preceded by a TAI64N timestamp (and a space) before being processed by the next action directive.

  • iso

  The selected line will be preceded by a ISO 8601 timestamp for combined date and time representing local time according to the systems timezone, with a space (not a T) between the date and the time and two spaces after the time, before being processed by the next action directive.

  • none

  The logged line will not be preceded by any timestamp.

  The following are two possible examples for the logger(frontend.html#Section: [logger]) section definition.

      [logger]
      @build = auto
      @runas = user
      @timeout-finish = 10000
  
      @destination = /run/log
      @backup = 10
      @timestamp = iso

      [logger]
      @build = auto
      @timestamp = iso

---

Section: [environment]

This section is optional.

A file containing the key=value pair(s) will be created by default at %%service_admconf%%/name_of_service directory. The default can also be changed at compile-time by passing the --with-sysadmin-service-conf=DIR option to ./configure.

Valid key names:

• Any key=value pair

  mandatory : no

  syntax : pair

  valid value :

  • You can define any variables that you want to add to the environment of the service. For example:

      [environment]
      dir_run=/run/openntpd
      cmd_args=-d -s

  The ! character can be put in front of the value. Do not put space between the exclamation mark and the value.

  For example, the following is valid:

      [environment]
      dir_run=!/run/openntpd
      cmd_args = !-d -s

  where:

      [environment]
      dir_run=! /run/openntpd
      cmd_args = ! -d -s

  is not.

  This will explicitly not set the value of the key for the runtime process but only at the start of the service. In this example the key=value pair passed to the command line does not need to be present in the general environment variable of the service.

---

Section: [regex]

This section is optional.

It will only have an effect when the service is a module type—see the section Module service creation.

You can use the @I string as key field. It will be replaced by the module name as you do for instantiated service before applying the regex section.

Valid key names:

• @configure

  mandatory : no

  syntax : quotes

  valid value :

  • You can define any arguments to pass to the module's configure script.

  ---

• @directories

  mandatory : no

  syntax : pair inside bracket

  valid value :

  • Any key=value pair where key is the regex to search on the directory name and value the replacement of that regex. For example:

      @directories = ( DM=sddm TRACKER=consolekit )

  Where the module directory contains two sub-directories named use-DM and by-TRACKER directories. It will be renamed as use-sddm and by-consolekit respectively.

  ---

• @files

  mandatory : no

  syntax : pair inside bracket

  valid value :

  • Reacts exactly as @directories field but on filename instead of directories name.

  ---

• @infiles

  mandatory : no

  syntax : colon

  valid value :

  • Any valid filename between the double colon with any key=value pair where key is the regex to search inside the file and value the replacement of that regex. The double colon must be present but the name between it can be omitted. In that case, the key=value pair will apply to all files contained on the module directories and to all keys (regex) found inside the same file.For example:

  @infiles = ( :mount-tmp:args=-o noexec
  ::user=@I )

  • It replaces first the term @I by the name of the module.
  • It opens the file named mount-tmp, search for the args regex and replaces it by the value of the regex.
  • It opens all files found on the module directory and replaces all regex 'user' found by the name of the module in each file.

  ---

---

A word about the @execute key

As described above the @execute key can be written in any language as long as you define the key @build as custom. For example if you want to write your @execute field with bash:

    @build = custom
    @execute = (
        #!/usr/bin/bash
        echo "This script displays available services"
        for i in $(ls %%service_system%%); do
            echo "daemon : ${i} is available"
        done
    )

This is an unnecessary example but it shows how to construct this use case. The resulting file will be :

    #!/usr/bin/bash
    echo "This script displays available services"
    for i in $(ls %%service_system%%); do
        echo "daemon : ${i} is available"
    done

When using this sort of custom function @runas has no effect. You must define with care what you want to happen in a custom case.

Furthermore when you set @build to auto the parser will take care about the redirection of the ouput of the service when the logger is activated. When setting @build to custom though the parser will not do this automatically. You need to explicitly tell it to:

    #!/usr/bin/bash
    exec 2>&1
    echo "This script redirects file descriptor 2 to the file descriptor 1"
    echo "Then the logger reads the file descriptor 1 and you have"
    echo "the error of the daemon written into the appropriate file"

Finally you need to take care about how you define your environment variable in the section environment(frontend.html#Section: [environment]). When setting @build to auto the parser will also take care about the ! character if you use it. This character will have no effect in the case of custom.

This same behavior applies to the logger(frontend.html#Section: [logger]) section. The fields @destination, @backup, @maxsize and @timestamp will have no effect in a custom case. You need to explicitly define the program to use the logger and the options for it in your @execute field.

---

Prototype of a frontend file

The minimal template is:

    [main]
    @type = classic,bundle,longrun,oneshot,module
    @version = 0.0.0
    @description = ""
    @user = ()

    [start]
    @execute = ()

This prototype contain all valid section with all valid key=value pair.

    [main]
    @type = classic,longrun,bundle,module
    @description = ""
    @version = 0.0.0
    @depends = ()
    @requiredby = ()
    @optsdepends = ()
    @options = ( log )
    @flags = ( down earlier )
    @notify =
    @user = ()
    @timeout-finish =
    @timeout-kill =
    @timeout-up =
    @timeout-down =
    @maxdeath =
    @down-signal =
    @hiercopy = ()
    @intree =

    [start]
    @build = auto,custom
    @runas =
    @execute = ()

    [stop]
    @build = auto,custom
    @runas =
    @execute = ()

    [logger]
    @build = auto,custom
    @runas =
    @destination = /path
    @backup =
    @maxsize =
    @timestamp =
    @timeout-finish =
    @timeout-kill =
    @execute = ()

    [environment]
    mykey=myvalue
    ANOTHERKEY=!antohervalue

    [regex]
    @configure = "arguments to pass to the configure script"
    @directories = ( key=value key=value )
    @files = ( key=value key=value )
    @infiles = ( :filename:key=value ::key=value )