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nix-channel: Add --rollback flag

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Fixes #368.
This commit is contained in:
Eelco Dolstra 2014-10-14 12:07:56 +02:00
parent c6849e2dee
commit 2c1711ae33
2 changed files with 68 additions and 1 deletions
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55
doc/manual/command-ref/nix-channel.xml
View file

@ -24,6 +24,7 @@
<arg choice='plain'><option>--remove</option> <replaceable>url</replaceable></arg>
<arg choice='plain'><option>--list</option></arg>
<arg choice='plain'><option>--update</option> <arg rep='repeat'><replaceable>names</replaceable></arg></arg>
<arg choice='plain'><option>--rollback</option> <arg choice='opt'><replaceable>generation</replaceable></arg></arg>
</group>
</cmdsynopsis>
</refsynopsisdiv>
@ -80,6 +81,14 @@ condition="manual">See also <xref linkend="sec-channels"
</varlistentry>
<varlistentry><term><option>--rollback</option> [<replaceable>generation</replaceable>]</term>
<listitem><para>Reverts the previous call to <command>nix-channel
--update</command>. Optionally, you can specify a specific channel
generation number to restore.</para></listitem>
</varlistentry>
</variablelist>
</para>
@ -104,10 +113,54 @@ respectively.</para>
<para>To subscribe to the Nixpkgs channel and install the GNU Hello package:</para>
<screen>
$ nix-channel --add http://nixos.org/channels/nixpkgs-unstable
$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
$ nix-channel --update
$ nix-env -iA nixpkgs.hello</screen>
<para>You can revert channel updates using <option>--rollback</option>:</para>
<screen>
$ nix-instantiate --eval -E '(import &lt;nixpkgs> {}).lib.nixpkgsVersion'
"14.04.527.0e935f1"
$ nix-channel --rollback
switching from generation 483 to 482
$ nix-instantiate --eval -E '(import &lt;nixpkgs> {}).lib.nixpkgsVersion'
"14.04.526.dbadfad"
</screen>
</refsection>
<refsection><title>Files</title>
<variablelist>
<varlistentry><term><filename>/nix/var/nix/profiles/<replaceable>username</replaceable>/channels</filename></term>
<listitem><para><command>nix-channel</command> uses a
<command>nix-env</command> profile to keep track of previous
versions of the subscribed channels. Every time you run
<command>nix-channel --update</command>, a new channel generation
(that is, a symlink to the channel Nix expressions in the Nix store)
is created. This enables <command>nix-channel --rollback</command>
to revert to previous versions.</para></listitem>
</varlistentry>
<varlistentry><term><filename>~/.nix-defexpr/channels</filename></term>
<listitem><para>This is a symlink to
<filename>/nix/var/nix/profiles/<replaceable>username</replaceable>/channels</filename>. It
ensures that <command>nix-env</command> can find your channels. In
a multi-user installation, you may also have
<filename>~/.nix-defexpr/channels_root</filename>, which links to
the channels of the root user.</para></listitem>
</varlistentry>
</variablelist>
</refsection>
</refentry>

14
scripts/nix-channel.in
View file

@ -199,6 +199,20 @@ while (scalar @ARGV) {
last;
}
elsif ($arg eq "--rollback") {
die "$0: ‘--rollback’ has at most one argument\n" if scalar @ARGV > 1;
my $generation = shift @ARGV;
my @args = ("$Nix::Config::binDir/nix-env", "--profile", $profile);
if (defined $generation) {
die "invalid channel generation number ‘$generation’" unless $generation =~ /^[0-9]+$/;
push @args, "--switch-generation", $generation;
} else {
push @args, "--rollback";
}
system(@args) == 0 or exit 1;
last;
}
elsif ($arg eq "--help") {
exec "man nix-channel" or die;
}