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The restore command is implemented entirely in C.

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For the most part this is a direct migration of the Perl code into C.

There is one important behavioral change with regard to how file permissions are handled.  The Perl code tried to set ownership as it was in the manifest even when running as an unprivileged user.  This usually just led to errors and frustration.

The C code works like this:

If a restore is run as a non-root user (the typical scenario) then all files restored will belong to the user/group executing pgBackRest. If existing files are not owned by the executing user/group then an error will result if the ownership cannot be updated to the executing user/group. In that case the file ownership will need to be updated by a privileged user before the restore can be retried.

If a restore is run as the root user then pgBackRest will attempt to recreate the ownership recorded in the manifest when the backup was made. Only user/group names are stored in the manifest so the same names must exist on the restore host for this to work. If the user/group name cannot be found locally then the user/group of the PostgreSQL data directory will be used and finally root if the data directory user/group cannot be mapped to a name.

Reviewed by Cynthia Shang.
This commit is contained in:
David Steele
2019-09-26 07:52:02 -04:00
parent 92e48c856a
commit 451ae397be
20 changed files with 4162 additions and 3057 deletions
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doc/xml/user-guide.xml
+10 -1
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@@ -1644,6 +1644,15 @@
<p>The Restore section introduces additional <cmd>restore</cmd> command features.</p>
<!-- ******************************************************************************************************************* -->
<section id="ownership">
<title>File Ownership</title>
<p>If a <cmd>restore</cmd> is run as a non-root user (the typical scenario) then all files restored will belong to the user/group executing <backrest/>. If existing files are not owned by the executing user/group then an error will result if the ownership cannot be updated to the executing user/group. In that case the file ownership will need to be updated by a privileged user before the restore can be retried.</p>
<p>If a <cmd>restore</cmd> is run as the <id>root</id> user then <backrest/> will attempt to recreate the ownership recorded in the manifest when the backup was made. Only user/group <b>names</b> are stored in the manifest so the same names must exist on the restore host for this to work. If the user/group name cannot be found locally then the user/group of the <postgres/> data directory will be used and finally <id>root</id> if the data directory user/group cannot be mapped to a name.</p>
</section>
<!-- SECTION => RESTORE - DELTA -->
<section id="option-delta">
<title>Delta Option</title>
@@ -1660,7 +1669,7 @@
<execute user="postgres" output="y" filter="y">
<exe-cmd>{[project-exe]} {[dash]}-stanza={[postgres-cluster-demo]} {[dash]}-delta
--log-level-console=detail restore</exe-cmd>
<exe-highlight>demo\/PG_VERSION - exists and matches backup|check\/clean db path|restore global\/pg_control</exe-highlight>
<exe-highlight>demo\/PG_VERSION - exists and matches backup|remove invalid files|rename global\/pg_control</exe-highlight>
</execute>
</execute-list>