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overview-manual: Updated "Fakeroot and Pseudo" section

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I added a bit more detail and some better referencing for Pseudo
and Fakeroot.

(From yocto-docs rev: 459ba368cce50cca1c3b9b7f13b1ec59a7d933ad)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2018-01-12 11:47:46 -08:00
committed by Richard Purdie
parent 9b4575b508
commit e4948134a8
1 changed files with 31 additions and 23 deletions
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documentation/overview-manual/overview-concepts.xml
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@@ -1258,11 +1258,15 @@
<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.
operations that are normally reserved for the root user (e.g.
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-install'><filename>do_install</filename></ulink>,
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-package_write_deb'><filename>do_package_write*</filename></ulink>,
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-rootfs'><filename>do_rootfs</filename></ulink>,
and
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-image'><filename>do_image*</filename></ulink>).
For example, the <filename>do_install</filename> task benefits
from being able to set the UID and GID of installed files to
arbitrary values.
</para>
<para>
@@ -1281,32 +1285,34 @@
<para>
The capability to run tasks in a fake root environment is known as
"fakeroot", which is derived from the BitBake keyword/variable
"<ulink url='http://man.he.net/man1/fakeroot'>fakeroot</ulink>",
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.
In the OpenEmbedded build system, the program that implements
fakeroot is known as Pseudo.
Pseudo overrides system calls by using the environment variable
<filename>LD_PRELOAD</filename>, which results in 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.
from operations that require root permissions, Pseudo uses
an SQLite 3 database.
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.
gives persistence between tasks and builds, which is not
accomplished using fakeroot.
<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
directories as a fakeroot task, then that task also needs to
run under fakeroot.
Otherwise, the task cannot run root-only operations, and
cannot see the fake file ownership and permissions set by the
other task.
You need to also add a dependency on
<filename>virtual/fakeroot-native:do_populate_sysroot</filename>,
giving the following:
<literallayout class='monospaced'>
@@ -1319,9 +1325,11 @@
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.
You can also reference the
"<ulink url='http://www.ibm.com/developerworks/opensource/library/os-aapseudo1/index.html'>Pseudo</ulink>"
and
"<ulink url='https://github.com/wrpseudo/pseudo/wiki/WhyNotFakeroot'>Why Not Fakeroot?</ulink>"
articles for background information on Pseudo.
</para>
</section>