nix-store manipulate or query the Nix store nix-store --add-root path --indirect operation options arguments The command nix-store performs primitive operations on the Nix store. You generally do not need to run this command manually. nix-store takes exactly one operation flag which indicates the subcommand to be performed. These are documented below. This section lists the options that are common to all operations. These options are allowed for every subcommand, though they may not always have an effect. See also for a list of common options. --add-root path Causes the result of a realisation (--realise and --force-realise) to be registered as a root of the garbage collector (see ). The root is stored in path, which must be inside a directory that is scanned for roots by the garbage collector (i.e., typically in a subdirectory of /nix/var/nix/gcroots/) unless the --indirect flag is used. If there are multiple results, then multiple symlinks will be created by sequentially numbering symlinks beyond the first one (e.g., foo, foo-2, foo-3, and so on). --indirect In conjunction with --add-root, this option allows roots to be stored outside of the GC roots directory. This is useful for commands such as nix-build that place a symlink to the build result in the current directory; such a build result should not be garbage-collected unless the symlink is removed. The --indirect flag causes a uniquely named symlink to path to be stored in /nix/var/nix/gcroots/auto/. For instance, $ nix-store --add-root /home/eelco/bla/result --indirect -r ... $ ls -l /nix/var/nix/gcroots/auto lrwxrwxrwx 1 ... 2005-03-13 21:10 dn54lcypm8f8... -> /home/eelco/bla/result $ ls -l /home/eelco/bla/result lrwxrwxrwx 1 ... 2005-03-13 21:10 /home/eelco/bla/result -> /nix/store/1r11343n6qd4...-f-spot-0.0.10 Thus, when /home/eelco/bla/result is removed, the GC root in the auto directory becomes a dangling symlink and will be ignored by the collector. Note that it is not possible to move or rename indirect GC roots, since the symlink in the auto directory will still point to the old location. nix-store --realise -r paths The operation --realise essentially “builds” the specified store paths. Realisation is a somewhat overloaded term: If the store path is a derivation, realisation ensures that the output paths of the derivation are valid (i.e., the output path and its closure exist in the file system). This can be done in several ways. First, it is possible that the outputs are already valid, in which case we are done immediately. Otherwise, there may be substitutes that produce the outputs (e.g., by downloading them). Finally, the outputs can be produced by performing the build action described by the derivation. If the store path is not a derivation, realisation ensures that the specified path is valid (i.e., it and its closure exist in the file system). If the path is already valid, we are done immediately. Otherwise, the path and any missing paths in its closure may be produced through substitutes. If there are no (succesful) subsitutes, realisation fails. The output path of each derivation is printed on standard output. (For non-derivations argument, the argument itself is printed.) This operation is typically used to build store derivations produced by nix-instantiate: $ nix-store -r $(nix-instantiate ./test.nix) /nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1 This is essentially what nix-build does. nix-store --gc --print-roots --print-live --print-dead --delete Without additional flags, the operation --gc performs a garbage collection on the Nix store. That is, all paths in the Nix store not reachable via file system references from a set of “roots”, are deleted. The following suboperations may be specified: --print-roots This operation prints on standard output the set of roots used by the garbage collector. What constitutes a root is described in . --print-live This operation prints on standard output the set of “live” store paths, which are all the store paths reachable from the roots. Live paths should never be deleted, since that would break consistency — it would become possible that applications are installed that reference things that are no longer present in the store. --print-dead This operation prints out on standard output the set of “dead” store paths, which is just the opposite of the set of live paths: any path in the store that is not live (with respect to the roots) is dead. --delete This operation performs an actual garbage collection. All dead paths are removed from the store. This is the default. The behaviour of the collector is influenced by the gc-keep-outputs and gc-keep-derivations variables in the Nix configuration file. With --delete, the collector prints the total number of freed bytes when it finishes (or when it is interrupted). With --print-dead, it prints the number of bytes that would be freed. To delete all unreachable paths, just do: $ nix-store --gc deleting `/nix/store/kq82idx6g0nyzsp2s14gfsc38npai7lf-cairo-1.0.4.tar.gz.drv' ... 8825586 bytes freed (8.42 MiB) nix-store --gc --ignore-liveness paths The operation --delete deletes the store paths paths from the Nix store, but only if it is safe to do so; that is, when the path is not reachable from a root of the garbage collector. This means that you can only delete paths that would also be deleted by nix-store --gc. Thus, --delete is a more targeted version of --gc. With the option --ignore-liveness, reachability from the roots is ignored. However, the path still won’t be deleted if there are other paths in the store that refer to it (i.e., depend on it). $ nix-store --delete /nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4 0 bytes freed (0.00 MiB) error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4' since it is still alive nix-store --query -q --outputs --requisites -R --references --referrers --referrers-closure --deriver --deriver --graph --tree --binding name --hash --use-output -u --force-realise -f paths The operation --query displays various bits of information about the store paths . The queries are described below. At most one query can be specified. The default query is --outputs. The paths paths may also be symlinks from outside of the Nix store, to the Nix store. In that case, the query is applied to the target of the symlink. --use-output -u For each argument to the query that is a store derivation, apply the query to the output path of the derivation instead. --force-realise -f Realise each argument to the query first (see nix-store --realise). --outputs Prints out the output paths of the store derivations paths. These are the paths that will be produced when the derivation is built. --requisites -R Prints out the closure of the store path paths. This query has one option: --include-outputs Also include the output path of store derivations, and their closures. This query can be used to implement various kinds of deployment. A source deployment is obtained by distributing the closure of a store derivation. A binary deployment is obtained by distributing the closure of an output path. A cache deployment (combined source/binary deployment, including binaries of build-time-only dependencies) is obtained by distributing the closure of a store derivation and specifying the option --include-outputs. --references Prints the set of references of the store paths paths, that is, their immediate dependencies. (For all dependencies, use --requisites.) --referrers Prints the set of referrers of the store paths paths, that is, the store paths currently existing in the Nix store that refer to one of paths. Note that contrary to the references, the set of referrers is not constant; it can change as store paths are added or removed. --referrers-closure Prints the closure of the set of store paths paths under the referrers relation; that is, all store paths that directly or indirectly refer to one of paths. These are all the path currently in the Nix store that are dependent on paths. --deriver Prints the deriver of the store paths paths. If the path has no deriver (e.g., if it is a source file), or if the deriver is not known (e.g., in the case of a binary-only deployment), the string unknown-deriver is printed. --graph Prints the references graph of the store paths paths in the format of the dot tool of AT&T's Graphviz package. This can be used to visualise dependency graphs. To obtain a build-time dependency graph, apply this to a store derivation. To obtain a runtime dependency graph, apply it to an output path. --tree Prints the references graph of the store paths paths as a nested ASCII tree. References are ordered by descending closure size; this tends to flatten the tree, making it more readable. The query only recurses into a store path when it is first encountered; this prevents a blowup of the tree representation of the graph. --binding name Prints the value of the attribute name (i.e., environment variable) of the store derivations paths. It is an error for a derivation to not have the specified attribute. --hash Prints the SHA-256 hash of the contents of the store path paths. Since the hash is stored in the Nix database, this is a fast operation. Print the closure (runtime dependencies) of the svn program in the current user environment: $ nix-store -qR $(which svn) /nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4 /nix/store/9lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4 ... Print the build-time dependencies of svn: $ nix-store -qR $(nix-store -qd $(which svn)) /nix/store/02iizgn86m42q905rddvg4ja975bk2i4-grep-2.5.1.tar.bz2.drv /nix/store/07a2bzxmzwz5hp58nf03pahrv2ygwgs3-gcc-wrapper.sh /nix/store/0ma7c9wsbaxahwwl04gbw3fcd806ski4-glibc-2.3.4.drv ... lots of other paths ... The difference with the previous example is that we ask the closure of the derivation (-qd), not the closure of the output path that contains svn. Show the build-time dependencies as a tree: $ nix-store -q --tree $(nix-store -qd $(which svn)) /nix/store/7i5082kfb6yjbqdbiwdhhza0am2xvh6c-subversion-1.1.4.drv +---/nix/store/d8afh10z72n8l1cr5w42366abiblgn54-builder.sh +---/nix/store/fmzxmpjx2lh849ph0l36snfj9zdibw67-bash-3.0.drv | +---/nix/store/570hmhmx3v57605cqg9yfvvyh0nnb8k8-bash | +---/nix/store/p3srsbd8dx44v2pg6nbnszab5mcwx03v-builder.sh ... Show all paths that depend on the same OpenSSL library as svn: $ nix-store -q --referrers $(nix-store -q --binding openssl $(nix-store -qd $(which svn))) /nix/store/23ny9l9wixx21632y2wi4p585qhva1q8-sylpheed-1.0.0 /nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4 /nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3 /nix/store/l51240xqsgg8a7yrbqdx1rfzyv6l26fx-lynx-2.8.5 Show all paths that directly or indirectly depend on the Glibc (C library) used by svn: $ nix-store -q --referrers-closure $(ldd $(which svn) | grep /libc.so | awk '{print $3}') /nix/store/034a6h4vpz9kds5r6kzb9lhh81mscw43-libgnomeprintui-2.8.2 /nix/store/15l3yi0d45prm7a82pcrknxdh6nzmxza-gawk-3.1.4 ... Note that ldd is a command that prints out the dynamic libraries used by an ELF executable. Make a picture of the runtime dependency graph of the current user environment: $ nix-store -q --graph ~/.nix-profile | dot -Tps > graph.ps $ gv graph.ps nix-store --verify --check-contents The operation --verify verifies the internal consistency of the Nix database, and the consistency between the Nix database and the Nix store. Any inconsistencies encountered are automatically repaired. Inconsistencies are generally the result of the Nix store or database being modified by non-Nix tools, or of bugs in Nix itself. There is one option: --check-contents Checks that the contents of every valid store path has not been altered by computing a SHA-256 hash of the contents and comparing it with the hash stored in the Nix database at build time. Paths that have been modified are printed out. For large stores, --check-contents is obviously quite slow. nix-store --dump path The operation --dump produces a NAR (Nix ARchive) file containing the contents of the file system tree rooted at path. The archive is written to standard output. A NAR archive is like a TAR or Zip archive, but it contains only the information that Nix considers important. For instance, timestamps are elided because all files in the Nix store have their timestamp set to 0 anyway. Likewise, all permissions are left out except for the execute bit, because all files in the Nix store have 644 or 755 permission. Also, a NAR archive is canonical, meaning that “equal” paths always produce the same NAR archive. For instance, directory entries are always sorted so that the actual on-disk order doesn’t influence the result. This means that the cryptographic hash of a NAR dump of a path is usable as a fingerprint of the contents of the path. Indeed, the hashes of store paths stored in Nix’s database (see nix-store -q --hash) are SHA-256 hashes of the NAR dump of each store path. NAR archives support filenames of unlimited length and 64-bit file sizes. They can contain regular files, directories, and symbolic links, but not other types of files (such as device nodes). A Nix archive can be unpacked using nix-store --restore. nix-store --restore path The operation --restore unpacks a NAR archive to path, which must not already exist. The archive is read from standard input.