Getting Started With Nix Package Manager

Getting Started With Nix Package Manager

This tutorial explains how to do package management operations such as installing, removing, updating, and upgrading packages using Nix package manager. If you haven’t installed Nix package manager yet, refer our previous guide “Nix – A Powerful Package Manager For Linux And Unix”. As you might already know, you don’t need to be a root or sudo user to do all package management operations using Nix.

Getting Started With Nix Package Manager

Nix has many commands. The main command for the package management is nix-env. This command is used to list, install, update, rollback, remove, query packages. Let us see some commands with examples.

Updating Nix channels

A Nix channel is just a URL that points to a place that contains a set of Nix expressions and a manifest. By default, Nixpkgs channel is automatically added to your list of “subscribed” channels when you install Nix.

To stay up to date with Nix channel, run the following command:

nix-channel --update

Sample output:

downloading Nix expressions from ‘https://d3g5gsiof5omrk.cloudfront.net/nixpkgs/nixpkgs-17.09pre108299.ec9a23332f/nixexprs.tar.xz’...
downloading ‘https://d3g5gsiof5omrk.cloudfront.net/nixpkgs/nixpkgs-17.09pre108299.ec9a23332f/nixexprs.tar.xz’... [8335/8656 KiB, 206.5 KiB/s]
unpacking channels...

You can also manually add a channel to your system as shown below.

nix-channel --add https://nixos.org/channels/nixpkgs-unstable

After subscribing(adding) a channel, do not forget to update the channel to obtain the latest available Nix expressions using command:

nix-channel --update

To remove a channel, just run:

nix-channel --remove nixpkgs

Search/query available packages

To view the list of available packages in the subscribed channel, run:

nix-env -qa

Sample output of the above command would be:

2048-in-terminal-2015-01-15
2bwm-0.2
389-ds-base-1.3.5.15
3dpong-0.5
4store-1.1.6
8086tiny-1.25
90secondportraits-1.01b
915resolution-0.5.3
9pfs
a2jmidid-8
a2ps-4.14
a52dec-0.7.4p4
aacgain-1.9.0
aacskeys-0.4.0e
aalib-1.4rc5
abc-verifier-20160818
abcde-2.7.2
abcl-1.4.0

[...]

Here, “-q” indicates the query operation. “-a” indicates all available (i.e., installable) packages.

You can query a particular package, as shown below.

nix-env -qa chromium

Output:

chromium-58.0.3029.110

Also, you can use the following command to search for a particular package.

nix-env -qaP | grep python3-3

Sample output:

nixpkgs.python33 python3-3.3.6
nixpkgs.python33Full python3-3.3.6
nixpkgs.python34 python3-3.4.6
nixpkgs.python34Full python3-3.4.6
nixpkgs.python35 python3-3.5.3
nixpkgs.python35Full python3-3.5.3
nixpkgs.python3Full python3-3.6.1
nixpkgs.python36Full python3-3.6.1
nixpkgs.python3 python3-3.6.1

To list all installed packages, simply run:

nix-env -q

It is also possible to see the status of the available package. Look at the below example.

nix-env -qas gcc

Sample output:

IPS gcc-5.4.0

Here, “I” indicates that the specified package is installed, “P” indicates the package is present on our system, and “S” indicates that whether there is a so-called substitute for the package.

You can query/list packages using regular expressions. Here are some examples of regular expressions.

chromium

Matches the package name chromium and any version.

chromium-58.0

Matches the package name chromium and version 58.0.

Example:

nix-env -qa chromium-58.0

gtk\\+

Matches the package name gtk+. The + character must be escaped using a backslash to prevent it from being interpreted as a quantifier, and the backslash must be escaped in turn with another backslash to ensure that the shell passes it on.

.\*

Matches any package name. This is the default for most commands.

‘.*zip.*’

Matches any package name containing the string zip. Note the dots: ‘*zip*’ does not work, because in a regular expression, the character * is interpreted as a quantifier.

‘.*(firefox|chromium).*’

Matches any package name containing the strings firefox or chromium.

Installing packages

As I mentioned in the previous tutorial, all packages will be stored in Nix Store, usually the directory /nix/store.

To install a package, just run:

nix-env --install gcc

Or,

nix-env -i gcc

The above command will install the latest available gcc package.

Sample output of the above command would be:

installing ‘gcc-5.4.0’
download-from-binary-cache.pl: still waiting for ‘https://cache.nixos.org/zx0i63k1qswsfjj3kxhwk1vqa9i5ys8i.narinfo’ after 5 seconds...
download-from-binary-cache.pl: still waiting for ‘https://cache.nixos.org/dyj2k6ch35r1ips4vr97md2i0yvl4r5c.narinfo’ after 5 seconds...
download-from-binary-cache.pl: still waiting for ‘https://cache.nixos.org/g25gnfmd8i392ahiip9nwfv80szqbkcs.narinfo’ after 5 seconds...
these paths will be fetched (38.94 MiB download, 150.45 MiB unpacked):
 /nix/store/7n45x3waczv1smsdkax2dy4j2zhbfk82-glibc-2.25-bin
 /nix/store/dyj2k6ch35r1ips4vr97md2i0yvl4r5c-gcc-5.4.0
 /nix/store/f05gsfcilsczwic8aga0cgl0sygbw5lc-zlib-1.2.11
 /nix/store/f111ij1fc83965m48bf2zqgiaq88fqv5-glibc-2.25
 /nix/store/g25gnfmd8i392ahiip9nwfv80szqbkcs-gcc-5.4.0-man
 /nix/store/n5k6yqf81jp4qbay2czaqciimhxikcq8-linux-headers-4.4.10
 /nix/store/vrr9maj9lqj2xwndlx3kh07vhnc111i2-glibc-2.25-dev
 /nix/store/xfrkm34sk0a13ha9bpki61l2k5g1v8dh-gcc-5.4.0-lib
 /nix/store/zx0i63k1qswsfjj3kxhwk1vqa9i5ys8i-gcc-5.4.0-info
fetching path ‘/nix/store/zx0i63k1qswsfjj3kxhwk1vqa9i5ys8i-gcc-5.4.0-info’...

[...]

fetching path ‘/nix/store/dyj2k6ch35r1ips4vr97md2i0yvl4r5c-gcc-5.4.0’...

*** Downloading ‘https://cache.nixos.org/nar/00y98z7i8a1a8d3nkv4dbbfbwwvznccbvmjdhaay0gqc0gfgb020.nar.xz’ to ‘/nix/store/dyj2k6ch35r1ips4vr97md2i0yvl4r5c-gcc-5.4.0’...
 % Total % Received % Xferd Average Speed Time Time Time Current
 Dload Upload Total Spent Left Speed
100 29.5M 100 29.5M 0 0 373k 0 0:01:21 0:01:21 --:--:-- 365k

building path(s) ‘/nix/store/nxx0bfg3n685fl0l3m2gbjqannh0wb9i-user-environment’
created 78 symlinks in user environment

Let us check if gcc is installed or not using command:

gcc -v

Sample output:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/nix/store/dyj2k6ch35r1ips4vr97md2i0yvl4r5c-gcc-5.4.0/libexec/gcc/x86_64-unknown-linux-gnu/5.4.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: 
Thread model: posix
gcc version 5.4.0 (GCC)

As you noticed in the above output, the gcc has been in a sub-directory named “dyj2k6ch35r1ips4vr97md2i0yvl4r5c-gcc-5.4.0” under /nix/store. Here, we call dyj2k6ch35r1ips4vr97md2i0yvl4r5c-gcc-5.4.0 as unique identifier. This subdirectory holds all required dependencies and libraries of gcc package.

Test packages without installing

Another notable feature of Nix package manager is that you can test a package without installing it on your system.

nix-shell -p gcc

This command builds or downloads gcc package and its dependencies, then drops you into a Bash shell where the gcc command is present, all without affecting your normal environment.

Once you done with testing, you can go back by simply typing exit.

[nix-shell:~]$ exit
exit

Upgrading packages

To upgrade a package to the next available version, just run:

nix-env --upgrade vim

Or, just:

nix-env -u vim

The above command will only upgrade vim package if there is a “newer” version.

Also, you can upgrade all installed packages at once by running the following command:

nix-env -u

Rollback packages

You installed a package, but it is not useful or not working properly. You need the lower version of the same package. What will you do? Simple. Just rollback to the previous working version using the following command:

nix-env --rollback

Uninstalling packages

To uninstall a package, run:

nix-env -e gcc

The above command will uninstall the package called gcc from your system.

You can remove multiple packages as shown below.

nix-env -e gcc vim

Sample output:

uninstalling ‘vim-8.0.0442’
uninstalling ‘gcc-5.4.0’
building path(s) ‘/nix/store/mxpikbq3l08379h8ik8mrj3fcw6mh6y4-user-environment’
created 6 symlinks in user environment

Removing unused packages

When a package is uninstalled, it’s not removed from Nix Store (i.e /nix/store/ directory). Only, the symlinks will removed from your profile.

To actually remove uninstalled packages, run:

nix-collect-garbage -d

Sample output:

finding garbage collector roots...
deleting garbage...
deleting ‘/nix/store/s4jr4dc9gghldr3xza23rw0gm9kp21kl-nix-prefetch-scripts.drv’
deleting ‘/nix/store/km2gyzlvs9vkrr52wxfyhinv4r52ksrj-nix-prefetch-bzr.drv’
deleting ‘/nix/store/7mi73sdc1p349vmpb5nyxsrv8ayk5hly-bazaar-2.7.0.drv’

[...]

deleting ‘/nix/store/8ckmcs9hx1qm0yxdnv892vrvx49zm1sq-setup-hook-2.0.sh’
deleting ‘/nix/store/trash’
deleting unused links...
note: currently hard linking saves -0.00 MiB
1447 store paths deleted, 12.65 MiB freed

You should run this command periodically to get rid of unused packages from your system.

And, that’s all for now. I hope you have got an idea of basic usage of Nix package manager. What I have just covered here are enough to get started with Nix package manager. Of course, there are many commands. To learn more Nix commands, refer the Nix official manual given at end of this guide.

If you find this guide useful, please share them on your social, professional networks and support OSTechNix. More good stuffs to come. Stay tuned!

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