mirror of
https://github.com/NixOS/nix.git
synced 2024-11-01 06:40:50 +00:00
* Profiles section.
This commit is contained in:
parent
b05a596d61
commit
cbe8de592d
@ -106,7 +106,7 @@ these files (and <filename>fetchurl.nix</filename> checks
|
||||
them).</para></listitem>
|
||||
|
||||
<listitem><para>We should switch away from MD5, since it has been
|
||||
cracked. We don't currently depend very much on the
|
||||
more-or-less cracked. We don't currently depend very much on the
|
||||
collision-resistance of MD5, but we will once we start sharing build
|
||||
results between users.</para></listitem>
|
||||
|
||||
|
@ -204,7 +204,7 @@ variables is to include the file
|
||||
in your <filename>~/.bashrc</filename> (or similar), like this:</para>
|
||||
|
||||
<screen>
|
||||
. <replaceable>prefix</replaceable>/etc/profile.d/nix.sh</screen>
|
||||
source <replaceable>prefix</replaceable>/etc/profile.d/nix.sh</screen>
|
||||
|
||||
</sect1>
|
||||
|
||||
|
@ -131,8 +131,8 @@ defined by some pretty much arbitrary rules regarding ordering of
|
||||
version numbers (which generally do what you'd expect of them). To
|
||||
just unconditionally replace Subversion with whatever version is in
|
||||
the Nix expressions, use <parameter>-i</parameter> instead of
|
||||
<parameter>-u</parameter> — <parameter>-i</parameter> will
|
||||
remove whatever version is already installed.</para>
|
||||
<parameter>-u</parameter>; <parameter>-i</parameter> will remove
|
||||
whatever version is already installed.</para>
|
||||
|
||||
<para>You can also upgrade all components for which there are newer
|
||||
versions:
|
||||
@ -142,7 +142,21 @@ $ nix-env -f nixpkgs-<replaceable>version</replaceable> -u '*'</screen>
|
||||
|
||||
</para>
|
||||
|
||||
<para>If you grow tired of specifying the Nix expressions using
|
||||
<para>Sometimes it's useful to be able to ask what
|
||||
<command>nix-env</command> would do, without actually doing it. For
|
||||
instance, to find out what packages would be upgraded by
|
||||
<literal>nix-env -u '*'</literal>, you can do
|
||||
|
||||
<screen>
|
||||
$ nix-env ... -u '*' --dry-run
|
||||
(dry run; not doing anything)
|
||||
upgrading `libxslt-1.1.0' to `libxslt-1.1.10'
|
||||
upgrading `graphviz-1.10' to `graphviz-1.12'
|
||||
upgrading `coreutils-5.0' to `coreutils-5.2.1'</screen>
|
||||
|
||||
</para>
|
||||
|
||||
<para>If you grow bored of specifying the Nix expressions using
|
||||
<parameter>-f</parameter> all the time, you can set a default
|
||||
location:
|
||||
|
||||
@ -162,14 +176,30 @@ set.</para></footnote></para>
|
||||
|
||||
<sect1><title>Profiles</title>
|
||||
|
||||
<para>In Nix, operations such as upgrading or removing components
|
||||
never overwrite or remove the files of those components, and they
|
||||
don't even touch the user environments that point to them. Rather,
|
||||
they cause a <emphasis>new</emphasis> user environment to be
|
||||
constructed based on the old one. This is illustrated in Figure
|
||||
bla.</para>
|
||||
<para>Profiles and user environments are Nix's mechanism for
|
||||
implementing the ability to allow differens users to have different
|
||||
configurations, and to do atomic upgrades and rollbacks. To
|
||||
understand how they work, it's useful to know a bit about how Nix
|
||||
works. In Nix, components are stored in unique locations in the
|
||||
<emphasis>Nix store</emphasis> (typically,
|
||||
<filename>/nix/store</filename>). For instance, a particular version
|
||||
of the Subversion component might be stored in a directory
|
||||
<filename>/nix/store/eeeeaf42e56b...-subversion-0.32.1/</filename>,
|
||||
while another version might be stored in
|
||||
<filename>/nix/store/58823d558a6a...-subversion-0.34/</filename>. The
|
||||
long hexadecimal numbers prefixed to the directory names are
|
||||
cryptographic hashes<footnote><para>128 bit MD5 hashes, to be
|
||||
precise.</para></footnote> of <emphasis>all</emphasis> inputs involved
|
||||
in building the component — sources, dependencies, compiler flags, and
|
||||
so on. So if two components differ in any way, they end up in
|
||||
different locations in the file system, so they don't interfere with
|
||||
each other. <xref linkend='fig-user-environments'
|
||||
/><footnote><para>TODO: the figure isn't entirely up to date. It
|
||||
should show multiple profiles and
|
||||
<filename>~/.nix-profile</filename>.</para></footnote> shows a part of
|
||||
a typical Nix store.</para>
|
||||
|
||||
<figure><title>User environments</title>
|
||||
<figure id='fig-user-environments'><title>User environments</title>
|
||||
<mediaobject>
|
||||
<imageobject>
|
||||
<imagedata fileref='figures/user-environments.png' format='PNG' />
|
||||
@ -177,20 +207,139 @@ bla.</para>
|
||||
</mediaobject>
|
||||
</figure>
|
||||
|
||||
<para>Of course, you wouldn't want to type
|
||||
|
||||
<screen>
|
||||
$ /nix/store/eeeeaf42e56b...-subversion-0.32.1/bin/svn</screen>
|
||||
|
||||
every time you want to run Subversion. Of course we could set up the
|
||||
<envar>PATH</envar> environment variable to include the
|
||||
<filename>bin</filename> directory of every component we want to use,
|
||||
but this is not very convenient since changing <envar>PATH</envar>
|
||||
doesn't take effect for already existing processes. The solution Nix
|
||||
uses is to create directory trees of symlinks to
|
||||
<emphasis>activated</emphasis> components. These are called
|
||||
<emphasis>user environments</emphasis> and they are components
|
||||
themselves (though automatically generated by
|
||||
<command>nix-env</command>), so they too reside in the Nix store. For
|
||||
instance, in <xref linkend='fig-user-environments' /> the user
|
||||
environment <filename>/nix/store/068150f63831...-user-env</filename>
|
||||
contains a symlink to just Subversion 0.32.1 (arrows in the figure
|
||||
indicate symlinks). This would be what we would obtain if we had done
|
||||
|
||||
<screen>
|
||||
$ nix-env -i subversion</screen>
|
||||
|
||||
on a set of Nix expressions that contained Subversion 0.32.1.</para>
|
||||
|
||||
<para>This doesn't in itself solve the problem, of course; you
|
||||
wouldn't want to type
|
||||
<filename>/nix/store/068150f63831...-user-env/bin/svn</filename>
|
||||
either. Therefore there are symlinks outside of the store that point
|
||||
to the user environments in the store; for instance, the symlinks
|
||||
<filename>42</filename> and <filename>43</filename> in the example.
|
||||
These are called <emphasis>generations</emphasis> since every time you
|
||||
perform a <command>nix-env</command> operation, a new user environment
|
||||
is generated based on the current one. For instance, generation 43
|
||||
was created from generation 42 when we did
|
||||
|
||||
<screen>
|
||||
$ nix-env -i subversion mozilla</screen>
|
||||
|
||||
on a set of Nix expressions that contained Mozilla and a new version
|
||||
of Subversion.</para>
|
||||
|
||||
<para>Generations are grouped together into
|
||||
<emphasis>profiles</emphasis> so that different users don't interfere
|
||||
with each other if they don't want to. For example:
|
||||
|
||||
<screen>
|
||||
$ ls -l /nix/var/nix/profiles/
|
||||
...
|
||||
lrwxrwxrwx 1 eelco ... default-42-link -> /nix/store/068150f63831...-user-env
|
||||
lrwxrwxrwx 1 eelco ... default-43-link -> /nix/store/84c85f89ddbf...-user-env
|
||||
lrwxrwxrwx 1 eelco ... default -> default-43-link</screen>
|
||||
|
||||
This shows a profile called <filename>default</filename>. The file
|
||||
<filename>default</filename> itself is actually a symlink that point
|
||||
to the current generation. When we do a <command>nix-env</command>
|
||||
operation, a new user environment and generation link are created
|
||||
based on the current one, and finally the <filename>default</filename>
|
||||
symlink is made to point at the new generation. This last step is
|
||||
atomic on Unix, which explains how we can do atomic upgrades. (Note
|
||||
that the building/installing of new components doesn't interfere in
|
||||
any way with old components, since they are stored in different
|
||||
locations in the Nix store.)</para>
|
||||
|
||||
<para>If you find that you want to undo a <command>nix-env</command>
|
||||
operation, you can just do
|
||||
|
||||
<screen>
|
||||
$ nix-env --rollback</screen>
|
||||
|
||||
which will just make the current generation link point at the previous
|
||||
link. E.g., <filename>default</filename> would be made to point at
|
||||
<filename>default-42-link</filename>. You can also switch to a
|
||||
specific generation:
|
||||
|
||||
<screen>
|
||||
$ nix-env --switch-generation 43</screen>
|
||||
|
||||
which in this example would roll forward to generation 43 again. You
|
||||
can also see all available generations:
|
||||
|
||||
<screen>
|
||||
$ nix-env --list-generations</screen></para>
|
||||
|
||||
<para>Actually, there is another level of indirection not shown in the
|
||||
figure above. You generally wouldn't have
|
||||
<filename>/nix/var/nix/profiles/<replaceable>some-profile</replaceable>/bin</filename>
|
||||
in your <envar>PATH</envar>. Rather, there is a symlink
|
||||
<filename>~/.nix-profile</filename> that point to your current
|
||||
profile. This means that you should put
|
||||
<filename>~/.nix-profile/bin</filename> in your <envar>PATH</envar>
|
||||
(and indeed, that's what the initialisation script
|
||||
<filename>/nix/etc/profile.d/nix.sh</filename> does). This makes it
|
||||
easier to switch to a different profile, which is exactly what the
|
||||
command <command>nix-env --switch-profile</command> does:
|
||||
|
||||
<screen>
|
||||
$ nix-env --switch-profile /nix/var/nix/profiles/my-profile
|
||||
|
||||
$ nix-env --switch-profile /nix/var/nix/profiles/default</screen>
|
||||
|
||||
These commands switch to the <filename>my-profile</filename> and
|
||||
default profile, respectively. If the profile doesn't exist, it will
|
||||
be created automatically. You should be careful about storing a
|
||||
profile in another location that the <filename>profiles</filename>
|
||||
directory, since otherwise it might not be used as a root to the
|
||||
garbage collection (see section <xref linkend='sec-garbage-collection'
|
||||
/>).</para>
|
||||
|
||||
<para>All <command>nix-env</command> operations work on the profile
|
||||
pointed to by <command>~/.nix-profile</command>, but you can override
|
||||
this on using the <option>--profile</option> option (abbreviation
|
||||
<option>-p</option>):
|
||||
|
||||
<screen>
|
||||
$ nix-env -p /nix/var/nix/profiles/other-profile -i subversion</screen>
|
||||
|
||||
This will <emphasis>not</emphasis> change the
|
||||
<command>~/.nix-profile</command> symlink.</para>
|
||||
|
||||
</sect1>
|
||||
|
||||
|
||||
<sect1><title>Garbage collection</title>
|
||||
<sect1 id='sec-garbage-collection'><title>Garbage collection</title>
|
||||
|
||||
<para>Bla</para>
|
||||
<para>TODO</para>
|
||||
|
||||
</sect1>
|
||||
|
||||
|
||||
<sect1><title>Channels</title>
|
||||
|
||||
<para>Bla</para>
|
||||
<para>TODO</para>
|
||||
|
||||
</sect1>
|
||||
|
||||
|
Loading…
Reference in New Issue
Block a user