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overview-manual, ref-manual: Moved Pseudo and Fakeroot to overview manual

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Fixes [YOCTO #12370]

The "Fakeroot and Pseudo" section is concepts and needed moved from the
ref-manual to the new concepts chapter of the overview-manual.  Some
links needed to be fixed as well.

(From yocto-docs rev: df2c09407abd5ca468fcd0bd9e241739907a9d63)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2018-01-11 11:17:06 -08:00
committed by Richard Purdie
parent a60d9e2917
commit 99980546fa
5 changed files with 76 additions and 76 deletions
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72
documentation/overview-manual/overview-concepts.xml
View File

@@ -1253,6 +1253,78 @@
</para>
</section>
<section id='fakeroot-and-pseudo'>
<title>Fakeroot and Pseudo</title>
<para>
Some tasks are easier to implement when allowed to perform certain
operations that are normally reserved for the root user.
For example, the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-install'><filename>do_install</filename></ulink>
task benefits from being able to set the UID and GID of installed
files to arbitrary values.
</para>
<para>
One approach to allowing tasks to perform root-only operations
would be to require BitBake to run as root.
However, this method is cumbersome and has security issues.
The approach that is actually used is to run tasks that benefit
from root privileges in a "fake" root environment.
Within this environment, the task and its child processes believe
that they are running as the root user, and see an internally
consistent view of the filesystem.
As long as generating the final output (e.g. a package or an image)
does not require root privileges, the fact that some earlier
steps ran in a fake root environment does not cause problems.
</para>
<para>
The capability to run tasks in a fake root environment is known as
"fakeroot", which is derived from the BitBake keyword/variable
flag that requests a fake root environment for a task.
In current versions of the OpenEmbedded build system,
the program that implements fakeroot is known as Pseudo.
</para>
<para>
Pseudo overrides system calls through the
<filename>LD_PRELOAD</filename> mechanism to give the
illusion of running as root.
To keep track of "fake" file ownership and permissions resulting
from operations that require root permissions, an sqlite3
database is used.
This database is stored in
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}/pseudo/files.db</filename>
for individual recipes.
Storing the database in a file as opposed to in memory
gives persistence between tasks, and even between builds.
<note><title>Caution</title>
If you add your own task that manipulates the same files or
directories as a fakeroot task, then that task should also run
under fakeroot.
Otherwise, the task will not be able to run root-only
operations, and will not see the fake file ownership and
permissions set by the other task.
You should also add a dependency on
<filename>virtual/fakeroot-native:do_populate_sysroot</filename>,
giving the following:
<literallayout class='monospaced'>
fakeroot do_mytask () {
...
}
do_mytask[depends] += "virtual/fakeroot-native:do_populate_sysroot"
</literallayout>
</note>
For more information, see the
<ulink url='&YOCTO_DOCS_BB_URL;#var-FAKEROOT'><filename>FAKEROOT*</filename></ulink>
variables in the BitBake User Manual.
You can also reference this
<ulink url='http://www.ibm.com/developerworks/opensource/library/os-aapseudo1/index.html'>Pseudo</ulink>
article.
</para>
</section>
<section id='x32'>
<title>x32 psABI</title>

2
documentation/ref-manual/ref-tasks.xml
View File

@@ -268,7 +268,7 @@
and
<link linkend='ref-tasks-rootfs'><filename>do_rootfs</filename></link>),
run under
<link linkend='fakeroot-and-pseudo'>fakeroot</link>.
<ulink url='&YOCTO_DOCS_OVERVIEW_URL;#fakeroot-and-pseudo'>fakeroot</ulink>.
<note>
<title>Caution</title>

2
documentation/ref-manual/ref-variables.xml
View File

@@ -3016,7 +3016,7 @@
<note><title>Caution</title>
Tasks that read from or write to this directory should
run under
<link linkend='fakeroot-and-pseudo'>fakeroot</link>.
<ulink url='&YOCTO_DOCS_OVERVIEW_URL;#fakeroot-and-pseudo'>fakeroot</ulink>.
</note>
</para>
</glossdef>

72
documentation/ref-manual/technical-details.xml
View File

@@ -13,78 +13,6 @@
x32, Wayland support, and Licenses.
</para>
<section id='fakeroot-and-pseudo'>
<title>Fakeroot and Pseudo</title>
<para>
Some tasks are easier to implement when allowed to perform certain
operations that are normally reserved for the root user.
For example, the
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
task benefits from being able to set the UID and GID of installed files
to arbitrary values.
</para>
<para>
One approach to allowing tasks to perform root-only operations
would be to require BitBake to run as root.
However, this method is cumbersome and has security issues.
The approach that is actually used is to run tasks that benefit from
root privileges in a "fake" root environment.
Within this environment, the task and its child processes believe that
they are running as the root user, and see an internally consistent
view of the filesystem.
As long as generating the final output (e.g. a package or an image)
does not require root privileges, the fact that some earlier steps ran
in a fake root environment does not cause problems.
</para>
<para>
The capability to run tasks in a fake root environment is known as
"fakeroot", which is derived from the BitBake keyword/variable
flag that requests a fake root environment for a task.
In current versions of the OpenEmbedded build system,
the program that implements fakeroot is known as Pseudo.
</para>
<para>
Pseudo overrides system calls through the
<filename>LD_PRELOAD</filename> mechanism to give the
illusion of running as root.
To keep track of "fake" file ownership and permissions resulting from
operations that require root permissions, an sqlite3
database is used.
This database is stored in
<filename>${</filename><link linkend='var-WORKDIR'><filename>WORKDIR</filename></link><filename>}/pseudo/files.db</filename>
for individual recipes.
Storing the database in a file as opposed to in memory
gives persistence between tasks, and even between builds.
<note><title>Caution</title>
If you add your own task that manipulates the same files or
directories as a fakeroot task, then that task should also run
under fakeroot.
Otherwise, the task will not be able to run root-only operations,
and will not see the fake file ownership and permissions set by the
other task.
You should also add a dependency on
<filename>virtual/fakeroot-native:do_populate_sysroot</filename>,
giving the following:
<literallayout class='monospaced'>
fakeroot do_mytask () {
...
}
do_mytask[depends] += "virtual/fakeroot-native:do_populate_sysroot"
</literallayout>
</note>
For more information, see the
<ulink url='&YOCTO_DOCS_BB_URL;#var-FAKEROOT'><filename>FAKEROOT*</filename></ulink>
variables in the BitBake User Manual.
You can also reference this
<ulink url='http://www.ibm.com/developerworks/opensource/library/os-aapseudo1/index.html'>Pseudo</ulink>
article.
</para>
</section>
<section id="wayland">
<title>Wayland</title>

4
documentation/yocto-project-qs/qs.xml
View File

@@ -1088,8 +1088,8 @@
I don't have much on this in the manual set.
Is there any more information we can leverage?
For information on Fakeroot and Pseudo, see the
"<ulink url='&YOCTO_DOCS_REF_URL;#fakeroot-and-pseudo'>Fakeroot and Pseudo</ulink>"
section in the Yocto Project Reference Manual.
"<ulink url='&YOCTO_DOCS_OVERVIEW_URL;#fakeroot-and-pseudo'>Fakeroot and Pseudo</ulink>"
section in the Yocto Project Overview Manual.
</para></listitem>
<listitem><para role='writernotes'>
<emphasis>OPKG:</emphasis>