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Diffstat (limited to 'doc/manual/opt-common.xml')
| -rw-r--r-- | doc/manual/opt-common.xml | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/doc/manual/opt-common.xml b/doc/manual/opt-common.xml index 158e282fdb55..db8a60ecad6e 100644 --- a/doc/manual/opt-common.xml +++ b/doc/manual/opt-common.xml @@ -147,3 +147,28 @@ </listitem> </varlistentry> + +<varlistentry> + <term><option>--fallback</option></term> + <listitem> + <para> + Whenever Nix attempts to realise a derivation for which a + closure is already known, but this closure cannot be realised, + fall back on normalising the derivation. + </para> + + <para> + The most common scenario in which this is useful is when we have + registered substitutes in order to perform binary distribution + from, say, a network repository. If the repository is down, the + realisation of the derivation will fail. When this option is + specified, Nix will build the derivation instead. Thus, + binary installation falls back on a source installation. This + option is not the default since it is generally not desirable + for a transient failure in obtaining the substitutes to lead to + a full build from source (with the related consumption of + resources). + </para> + </listitem> +</varlistentry> + |