Environment variables: Difference between revisions
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= | == Configuration of shell environment on NixOS == | ||
Environment variables can be set with <code>environment.variables</code>, <code>environment.sessionVariables</code> | Environment variables can be set with [https://search.nixos.org/options?channel=unstable&show=environment.variables&from=0&size=50&sort=relevance&type=packages&query=environment.variables environment.variables ], [https://search.nixos.org/options?channel=unstable&show=environment.sessionVariables&from=0&size=50&sort=relevance&type=packages&query=environment.sessionVariables environment.sessionVariables ], and [https://search.nixos.org/options?channel=unstable&show=environment.profileRelativeSessionVariables&from=0&size=50&sort=relevance&type=packages&query=environment.profileRelativeSessionVariables environment.profileRelativeSessionVariables ] . | ||
<code>environment.variables</code> are global variables set on shell initialization, whereas <code>environment.sessionVariables</code> and <code>environment.profileRelativeSessionVariables</code> are initialized through PAM (Pluggable Authentication Module). | |||
For example, for the [https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html#variables XDG Base Directory Specification], the following could be set to <code>/etc/nixos/configuration.nix</code>: | |||
<syntaxhighlight lang="nix"> | <syntaxhighlight lang="nix"> | ||
{ | { | ||
# ... | |||
# This is using a rec (recursive) expression to set and access XDG_BIN_HOME within the expression | |||
# For more on rec expressions see https://nix.dev/tutorials/first-steps/nix-language#recursive-attribute-set-rec | |||
environment.sessionVariables = rec { | environment.sessionVariables = rec { | ||
XDG_CACHE_HOME = " | XDG_CACHE_HOME = "$HOME/.cache"; | ||
XDG_CONFIG_HOME = " | XDG_CONFIG_HOME = "$HOME/.config"; | ||
XDG_DATA_HOME = "$HOME/.local/share"; | |||
XDG_STATE_HOME = "$HOME/.local/state"; | |||
# Not officially in the specification | |||
XDG_BIN_HOME = "$HOME/.local/bin"; | |||
PATH = [ | PATH = [ | ||
" | "${XDG_BIN_HOME}" | ||
]; | ]; | ||
}; | }; | ||
Line 21: | Line 28: | ||
} | } | ||
</syntaxhighlight> | </syntaxhighlight> | ||
== Troubleshooting == | |||
=== pam_env(sudo:session): Expandable variables must be wrapped in {} <$VARIABLE/path/to> === | |||
Error logs may be found with <code>journalctl -xb -p3</code> regarding the no presence of curly braces <code>{}</code> for variable expansion. | |||
<syntaxhighlight lang="shell"> | |||
sudo[3424]: pam_env(sudo:session): Expandable variables must be wrapped in {} <$VARIABLE/path/to> - ignoring | |||
</syntaxhighlight> | |||
While checking the configuration values, for instance with <code>nixos-option environment.sessionVariables</code>, it might be found that Nix is correctly parsing the curly braces. | |||
<syntaxhighlight lang="nix"> | |||
Value: | |||
{ | |||
... | |||
VARIABLE = "${VARIABLE}/path/to"; | |||
... | |||
} | |||
</syntaxhighlight> | |||
This indicates that the curly braces are getting removed at a later stage. | |||
==== Solution or workaround ==== | |||
Unknown. | |||
== Using variables from a Nix expression == | |||
The <code>builtins.getEnv</code> function allows for reading the environment of the Nix command which triggered the expression to be evaluated, typically <code>nix-build</code>. | |||
== Variables exposed in nix-build sandbox == | |||
Compared to a normal shell environment, in a nix-build sandbox, | |||
Nix will set some environment variables, for example: | |||
<pre> | |||
NIX_BINTOOLS=/nix/store/lvg99f3zni6zw4cvlci6wpmzlls0nsn4-binutils-wrapper-2.38 | |||
NIX_BINTOOLS_WRAPPER_TARGET_HOST_x86_64_unknown_linux_gnu=1 | |||
NIX_BUILD_CORES=3 | |||
NIX_BUILD_TOP=/build | |||
NIX_CC=/nix/store/61zfi5pmhb0d91422f186x26v7b52y5k-gcc-wrapper-11.3.0 | |||
NIX_CC_WRAPPER_TARGET_HOST_x86_64_unknown_linux_gnu=1 | |||
NIX_CFLAGS_COMPILE= -frandom-seed=8cnrgjjflj | |||
NIX_ENFORCE_NO_NATIVE=1 | |||
NIX_ENFORCE_PURITY=1 | |||
NIX_HARDENING_ENABLE=fortify stackprotector pic strictoverflow format relro bindnow | |||
NIX_INDENT_MAKE=1 | |||
NIX_LDFLAGS=-rpath /nix/store/8cnrgjjflj3dyppz299w50l9yydgnqkp-x/lib64 -rpath /nix/store/8cnrgjjflj3dyppz299w50l9yydgnqkp-x/lib | |||
NIX_LOG_FD=2 | |||
NIX_SSL_CERT_FILE=/no-cert-file.crt | |||
NIX_STORE=/nix/store | |||
</pre> |
Latest revision as of 05:45, 5 July 2024
Configuration of shell environment on NixOS
Environment variables can be set with environment.variables , environment.sessionVariables , and environment.profileRelativeSessionVariables .
environment.variables
are global variables set on shell initialization, whereas environment.sessionVariables
and environment.profileRelativeSessionVariables
are initialized through PAM (Pluggable Authentication Module).
For example, for the XDG Base Directory Specification, the following could be set to /etc/nixos/configuration.nix
:
{
# ...
# This is using a rec (recursive) expression to set and access XDG_BIN_HOME within the expression
# For more on rec expressions see https://nix.dev/tutorials/first-steps/nix-language#recursive-attribute-set-rec
environment.sessionVariables = rec {
XDG_CACHE_HOME = "$HOME/.cache";
XDG_CONFIG_HOME = "$HOME/.config";
XDG_DATA_HOME = "$HOME/.local/share";
XDG_STATE_HOME = "$HOME/.local/state";
# Not officially in the specification
XDG_BIN_HOME = "$HOME/.local/bin";
PATH = [
"${XDG_BIN_HOME}"
];
};
# ...
}
Troubleshooting
pam_env(sudo:session): Expandable variables must be wrapped in {} <$VARIABLE/path/to>
Error logs may be found with journalctl -xb -p3
regarding the no presence of curly braces {}
for variable expansion.
sudo[3424]: pam_env(sudo:session): Expandable variables must be wrapped in {} <$VARIABLE/path/to> - ignoring
While checking the configuration values, for instance with nixos-option environment.sessionVariables
, it might be found that Nix is correctly parsing the curly braces.
Value:
{
...
VARIABLE = "${VARIABLE}/path/to";
...
}
This indicates that the curly braces are getting removed at a later stage.
Solution or workaround
Unknown.
Using variables from a Nix expression
The builtins.getEnv
function allows for reading the environment of the Nix command which triggered the expression to be evaluated, typically nix-build
.
Variables exposed in nix-build sandbox
Compared to a normal shell environment, in a nix-build sandbox, Nix will set some environment variables, for example:
NIX_BINTOOLS=/nix/store/lvg99f3zni6zw4cvlci6wpmzlls0nsn4-binutils-wrapper-2.38 NIX_BINTOOLS_WRAPPER_TARGET_HOST_x86_64_unknown_linux_gnu=1 NIX_BUILD_CORES=3 NIX_BUILD_TOP=/build NIX_CC=/nix/store/61zfi5pmhb0d91422f186x26v7b52y5k-gcc-wrapper-11.3.0 NIX_CC_WRAPPER_TARGET_HOST_x86_64_unknown_linux_gnu=1 NIX_CFLAGS_COMPILE= -frandom-seed=8cnrgjjflj NIX_ENFORCE_NO_NATIVE=1 NIX_ENFORCE_PURITY=1 NIX_HARDENING_ENABLE=fortify stackprotector pic strictoverflow format relro bindnow NIX_INDENT_MAKE=1 NIX_LDFLAGS=-rpath /nix/store/8cnrgjjflj3dyppz299w50l9yydgnqkp-x/lib64 -rpath /nix/store/8cnrgjjflj3dyppz299w50l9yydgnqkp-x/lib NIX_LOG_FD=2 NIX_SSL_CERT_FILE=/no-cert-file.crt NIX_STORE=/nix/store