added a larger example

[rrq/overlay-boot.git] / overlay-boot.8.adoc

diff --git a/overlay-boot.8.adoc b/overlay-boot.8.adoc
index 9e39eec327e53c1c09e2c492f951f8a44de39095..b2a103299a5c690acbae5a1a0c5c44a6c570004d 100644 (file)
--- a/overlay-boot.8.adoc
+++ b/overlay-boot.8.adoc
@@ -24,7 +24,7 @@ an overlay of the main host filesystem to keep the specifics of a
 service distinctly separate from the main host while sharing files
 wherever sensible.
 
 service distinctly separate from the main host while sharing files
 wherever sensible.
 

-A subhost is started by identifyinf its configuration file on the
+A subhost is started by identifying its configuration file on the

 command line for *overlay-boot*. The configuration file is a plain
 text file with a small collection of "variables" that tell how the
 subhost is set up. When all is good, *overlay-boot* spawns a
 command line for *overlay-boot*. The configuration file is a plain
 text file with a small collection of "variables" that tell how the
 subhost is set up. When all is good, *overlay-boot* spawns a


@@ -34,7 +34,7 @@ odd computer.
 
 The subhost execution environment may be "entered" to perform
 adminstrative tasks with *overlay-go*, and it is later stopped with
 
 The subhost execution environment may be "entered" to perform
 adminstrative tasks with *overlay-go*, and it is later stopped with

-*overlay-stop*.
+*overlay-stop*. 

 
 OPTIONS
 -------
 
 OPTIONS
 -------


@@ -117,11 +117,11 @@ before the services are started. The default for this variable is
 This variable nominates the "upper" filesystem for an overlay mount.
 This will be accessed read-write and it constitutes the "private"
 files of the subhost.
 This variable nominates the "upper" filesystem for an overlay mount.
 This will be accessed read-write and it constitutes the "private"
 files of the subhost.

-
++

 If UPPER is different from LOWER, then the root file system is set up
 as an overlay mount. In that case WORK (below) must be defined as a
 directory outside of but on the same mount as UPPER.
 If UPPER is different from LOWER, then the root file system is set up
 as an overlay mount. In that case WORK (below) must be defined as a
 directory outside of but on the same mount as UPPER.

-
++

 If UPPER is the same as LOWER, then the subhost root filesystem is not
 setup as an overla. Rather it is set up as a bind mount, if UPPER is
 different from LIVE, or just as a pre-mounted LIVE filesystem.
 If UPPER is the same as LOWER, then the subhost root filesystem is not
 setup as an overla. Rather it is set up as a bind mount, if UPPER is
 different from LIVE, or just as a pre-mounted LIVE filesystem.


@@ -136,7 +136,7 @@ directory.
 
 This variable tells which services should be started on the
 overlay-boot startup. The default value is +networking ssh+.
 
 This variable tells which services should be started on the
 overlay-boot startup. The default value is +networking ssh+.

-
++

 Note that if no services are started, then +overlay-init+ starts a
 +dummy_service+ so as to keep +/.reaper+ from running out of child
 processes, as it otherwise will exit and thereby terminate
 Note that if no services are started, then +overlay-init+ starts a
 +dummy_service+ so as to keep +/.reaper+ from running out of child
 processes, as it otherwise will exit and thereby terminate


@@ -151,16 +151,16 @@ defult gets mounted on an overlay mount as a +tmpfs+ of 50M. Use
 Networking
 ----------
 
 Networking
 ----------
 

-*overlay-boot* sets up a nework namespace named by the subhost NAME,
-and uses the CABLES variable to set up +veth+ virtual cables. The host
-end of such cables are named by NAME followed by a number from 0 and
-up while the subhost end are named by +eth+ followed by the same
-number.
+*overlay-boot* sets up a nework namespace named by the subhost
++$NAME+, and uses the +$CABLES+ variable to set up +veth+ virtual
+cables. The host end of such cables are named by +$NAME+ followed by a
+number from 0 and up while the subhost end are named by +eth+ followed
+by the same number.

 
 

-As mentioned above, CABLES consists of a space separated list of cable
-specifiers, each consisting of a bridge interface name and a with an
-equal sign ("=") between them. The equal sign is required while either
-or both of the bridge and MAC address may be left empty.
+As mentioned above, +$CABLES+ consists of a space separated list of
+cable specifiers, each consisting of a bridge interface name and a
+with an equal sign ("=") between them. The equal sign is required
+while either or both of the bridge and MAC address may be left empty.

 
 The bridge interface name, if given, will be given control of the host
 end cable interface. A cable specification with empty bridge name part
 
 The bridge interface name, if given, will be given control of the host
 end cable interface. A cable specification with empty bridge name part


@@ -177,13 +177,43 @@ EXAMPLES
 
 ./opt/subhost/mta/mta.conf
 ****
 
 ./opt/subhost/mta/mta.conf
 ****

+----

 BASE=.
 BASE=.

-START= rsyslog newtorking ssh postfix
+CABLES= =
+START= rsyslog networking ssh saslauthd postfix dovecot
+----

 ****
 
 The above example assumes a directory +/opt/subhost/mta+ that contains
 the configuration file +mta.conf+ and directories +root+, +work+ and
 +live+. *overlay-boot* will set up an overlay mount on +live+ with
 +root+ as UPPER, +work+ as WORK and +/+ as LOWER, i.e. an overlay of
 ****
 
 The above example assumes a directory +/opt/subhost/mta+ that contains
 the configuration file +mta.conf+ and directories +root+, +work+ and
 +live+. *overlay-boot* will set up an overlay mount on +live+ with
 +root+ as UPPER, +work+ as WORK and +/+ as LOWER, i.e. an overlay of

-the main host filesystem.
+the main host filesystem. Further, the running subhost will feature a
+virtual cable to the main host, where the subhost end is named +eth0+
+and the main host end is named +mta0+, and upon start, an +ifup mta0+
+is attempted at the host end while the subhost end is handled via its
+neworking service.
+
+./opt/subhost/tiny/tiny.conf
+****
+----
+BASE=.
+CABLES= =
+START= none
+LOWER=!mkdir -p base work root live ; echo base
+WORK= work
+UPPER= root
+LIVE= live
+----
+****
+
+The +tiny+ subhost would be for overlaying a separate +debootstrap+
+root filesystem, without any services (since +START+ is empty). This
+gets started with a +dummy_service+ to hold the overlay for access via
++overlay-go+. The +dummy_service+ sets up and listens on a pipe at
++/run/dummy_service+, and exits when anything is written to that.
+
+SEE ALSO
+--------

 
 

+*overlay-stop*, *overlay-go*