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nix-store: make --dump-db take a list of paths to dump

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Inside a derivation, exportReferencesGraph already provides a way to
dump the Nix database for a specific closure. On the command line,
--dump-db gave us the same information, but only for the entire Nix
database at once.

With this change, one can now pass a list of paths to --dump-db to get
the Nix database dumped for just those paths. (The user is responsible
for ensuring this is a closure, like for --export).

Among other things, this is useful for deploying a closure to a new
host without using --import/--export; one can use tar to transfer the
store paths, and --dump-db/--load-db to transfer the validity
information. This is useful if the new host doesn't actually have Nix
yet, and the closure that is being deployed itself contains Nix.
This commit is contained in:
Spencer Baugh 2018-12-12 14:19:54 -05:00
parent 92d08c02c8
commit 5f1891b795
2 changed files with 18 additions and 5 deletions
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8
doc/manual/command-ref/nix-store.xml
View file

@ -1282,6 +1282,7 @@ ktorrent-2.2.1/NEWS
<cmdsynopsis>
<command>nix-store</command>
<arg choice='plain'><option>--dump-db</option></arg>
<arg rep='repeat'><replaceable>paths</replaceable></arg>
</cmdsynopsis>
</refsection>
@ -1292,6 +1293,13 @@ Nix database to standard output. It can be loaded into an empty Nix
store using <option>--load-db</option>. This is useful for making
backups and when migrating to different database schemas.</para>
<para>By default, <option>--dump-db</option> will dump the entire Nix
database. When one or more store paths is passed, only the subset of
the Nix database for those store paths is dumped. As with
<option>--export</option>, the user is responsible for passing all the
store paths for a closure. See <option>--export</option> for an
example.</para>
</refsection>
</refsection>

15
src/nix-store/nix-store.cc
View file

@ -485,11 +485,16 @@ static void opReadLog(Strings opFlags, Strings opArgs)
static void opDumpDB(Strings opFlags, Strings opArgs)
{
if (!opFlags.empty()) throw UsageError("unknown flag");
if (!opArgs.empty())
throw UsageError("no arguments expected");
PathSet validPaths = store->queryAllValidPaths();
for (auto & i : validPaths)
cout << store->makeValidityRegistration({i}, true, true);
if (!opArgs.empty()) {
for (auto & i : opArgs)
i = store->followLinksToStorePath(i);
for (auto & i : opArgs)
cout << store->makeValidityRegistration({i}, true, true);
} else {
PathSet validPaths = store->queryAllValidPaths();
for (auto & i : validPaths)
cout << store->makeValidityRegistration({i}, true, true);
}
}