diff options
Diffstat (limited to 'doc/manual/release-notes.xml')
| -rw-r--r-- | doc/manual/release-notes.xml | 156 |
1 files changed, 138 insertions, 18 deletions
diff --git a/doc/manual/release-notes.xml b/doc/manual/release-notes.xml index b64e2025c452..c2eaa28bc244 100644 --- a/doc/manual/release-notes.xml +++ b/doc/manual/release-notes.xml @@ -12,26 +12,85 @@ <itemizedlist> - <listitem><para>TODO: Berkeley DB no longer needed.</para></listitem> + <listitem> + <para>Nix no longer uses Berkeley DB to store Nix store metadata. + The principal advantages of the new storage scheme are: it works + properly over decent implementations of NFS (allowing Nix stores + to be shared between multiple machines); no recovery is needed + when a Nix process crashes; no write access is needed for + read-only operations; no more running out of Berkeley DB locks on + certain operations.</para> + + <para>You still need to compile Nix with Berkeley DB support if + you want Nix to automatically convert your old Nix store to the + new schema. If you don’t need this, you can build Nix with the + <filename>configure</filename> option + <option>--disable-old-db-compat</option>.</para> + + <para>After the automatic conversion to the new schema, you can + delete the old Berkeley DB files: - <listitem><para>New substituter to copy from remotely mounted Nix - stores (TODO: document).</para></listitem> + <screen> +$ cd /nix/var/nix/db +$ rm __db* log.* derivers references referrers reserved validpaths DB_CONFIG</screen> + + The new metadata is stored in the directories + <filename>/nix/var/nix/db/info</filename> and + <filename>/nix/var/nix/db/referrer</filename>. Though the + metadata is stored in human-readable plain-text files, they are + not intended to be human-editable, as Nix is rather strict about + the format.</para> + + <para>The new storage schema may or may not require less disk + space than the Berkeley DB environment, mostly depending on the + cluster size of your file system. With 1 KiB clusters (which + seems to be the <literal>ext3</literal> default nowadays) it + usually takes up much less space.</para> + </listitem> - <listitem><para><command>nix-store --dump-db / --load-db</command>.</para></listitem> + <listitem><para>There is a new substituter that copies paths + directly from other (remote) Nix stores mounted somewhere in the + filesystem. For instance, you can speed up an installation by + mounting some remote Nix store that already has the packages in + question via NFS or <literal>sshfs</literal>. The environment + variable <envar>NIX_OTHER_STORES</envar> specifies the locations of + the remote Nix directories, + e.g. <literal>/mnt/remote-fs/nix</literal>.</para></listitem> + + <listitem><para>New <command>nix-store</command> operations + <option>--dump-db</option> and <option>--load-db</option> to dump + and reload the Nix database.</para></listitem> + + <listitem><para>The garbage collector has a number of new options to + allow only some of the garbage to be deleted. The option + <option>--max-freed <replaceable>N</replaceable></option> tells the + collector to stop after at least <replaceable>N</replaceable> bytes + have been deleted. The option <option>--max-links + <replaceable>N</replaceable></option> tells it to stop after the + link count on <filename>/nix/store</filename> has dropped below + <replaceable>N</replaceable>. This is useful on very large Nix + stores on filesystems with a 32000 subdirectories limit (like + <literal>ext3</literal>). The option <option>--use-atime</option> + causes store paths to be deleted in order of ascending last access + time. This allows non-recently used stuff to be deleted. The + option <option>--max-atime <replaceable>time</replaceable></option> + specifies an upper limit to the last accessed time of paths that may + be deleted. For instance, - <listitem><para>New primops: - <varname>builtins.parseDrvName</varname>, - <varname>builtins.compareVersions</varname>, - <varname>builtins.length</varname>, - <varname>builtins.add</varname>, - <varname>builtins.sub</varname>, - <varname>builtins.genericClosure</varname>. - </para></listitem> + <screen> + $ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")</screen> - <listitem><para>GC options: <option>--max-freed</option>, - <option>--max-links</option>.</para></listitem> + deletes everything that hasn’t been accessed in two months.</para></listitem> - <listitem><para>TODO: Optimistic profile locking.</para></listitem> + <listitem><para><command>nix-env</command> now uses optimistic + profile locking when performing an operation like installing or + upgrading, instead of setting an exclusive lock on the profile. + This allows multiple <command>nix-env -i / -u / -e</command> + operations on the same profile in parallel. If a + <command>nix-env</command> operation sees at th end that the profile + was changed in the meantime by another process, it will just + restart. This is generally cheap because the build results are + still in the Nix store.</para></listitem> <listitem><para>The option <option>--dry-run</option> is now supported by <command>nix-store -r</command> and @@ -42,17 +101,78 @@ and which paths will be substituted) is now always shown by <command>nix-env</command>, <command>nix-store -r</command> and <command>nix-build</command>. The total download size of - substitutable paths is now also shown.</para></listitem> + substitutable paths is now also shown. For instance, a build will + show something like + + <screen> +the following derivations will be built: + /nix/store/129sbxnk5n466zg6r1qmq1xjv9zymyy7-activate-configuration.sh.drv + /nix/store/7mzy971rdm8l566ch8hgxaf89x7lr7ik-upstart-jobs.drv + ... +the following paths will be downloaded/copied (30.02 MiB): + /nix/store/4m8pvgy2dcjgppf5b4cj5l6wyshjhalj-samba-3.2.4 + /nix/store/7h1kwcj29ip8vk26rhmx6bfjraxp0g4l-libunwind-0.98.6 + ...</screen> + + </para></listitem> + + <listitem><para>Language features: + + <itemizedlist> + + <listitem><para>@-patterns as in Haskell. For instance, in a + function definition + + <programlisting>f = args @ {x, y, z}: <replaceable>...</replaceable>;</programlisting> + + <varname>args</varname> refers to the argument as a whole, which + is further pattern-matched against the attribute set pattern + <literal>{x, y, z}</literal>.</para></listitem> + + <listitem><para>“<literal>...</literal>” (ellipsis) patterns. + An attribute set pattern can now say <literal>...</literal> at + the end of the attribute name list to specify that the function + takes <emphasis>at least</emphasis> the listed attributes, while + ignoring additional attributes. For instance, + + <programlisting>{stdenv, fetchurl, fuse, ...}: <replaceable>...</replaceable></programlisting> + + defines a function that accepts any attribute set that includes + at least the three listed attributes.</para></listitem> + + <listitem><para>New primops: + <varname>builtins.parseDrvName</varname> (split a package name + string like <literal>"nix-0.12pre12876"</literal> into its name + and version components, e.g. <literal>"nix"</literal> and + <literal>"0.12pre12876"</literal>), + <varname>builtins.compareVersions</varname> (compare two version + strings using the same algorithm that <command>nix-env</command> + uses), <varname>builtins.length</varname> (efficiently compute + the length of a list), <varname>builtins.mul</varname> (integer + multiplication), <varname>builtins.div</varname> (integer + division). + <!-- <varname>builtins.genericClosure</varname> --> + </para></listitem> + + </itemizedlist> + + </para></listitem> <listitem><para><command>nix-prefetch-url</command> now supports - <literal>mirror://</literal> URLs.</para></listitem> + <literal>mirror://</literal> URLs, provided that the environment + variable <envar>NIXPKGS_ALL</envar> points at a Nixpkgs + tree.</para></listitem> <listitem><para>Removed the commands <command>nix-pack-closure</command> and <command>nix-unpack-closure</command>. You can do almost the same thing but much more efficiently by doing <literal>nix-store --export $(nix-store -qR <replaceable>paths</replaceable>) > closure</literal> and - <literal>nix-store --import < closure</literal>.</para></listitem> + <literal>nix-store --import < + closure</literal>.</para></listitem> + + <listitem><para>Lots of bugfixes, including a big performance bug in + the handling of <literal>with</literal>-expressions.</para></listitem> </itemizedlist> |