diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 4266a5474..aa695e174 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -269,16 +269,13 @@ bool isLink(const Path & path)
 }
 
 
-DirEntries readDirectory(const Path & path)
+DirEntries readDirectory(DIR *dir, const Path & path)
 {
     DirEntries entries;
     entries.reserve(64);
 
-    AutoCloseDir dir(opendir(path.c_str()));
-    if (!dir) throw SysError(format("opening directory '%1%'") % path);
-
     struct dirent * dirent;
-    while (errno = 0, dirent = readdir(dir.get())) { /* sic */
+    while (errno = 0, dirent = readdir(dir)) { /* sic */
         checkInterrupt();
         string name = dirent->d_name;
         if (name == "." || name == "..") continue;
@@ -295,6 +292,14 @@ DirEntries readDirectory(const Path & path)
     return entries;
 }
 
+DirEntries readDirectory(const Path & path)
+{
+    AutoCloseDir dir(opendir(path.c_str()));
+    if (!dir) throw SysError(format("opening directory '%1%'") % path);
+
+    return readDirectory(dir.get(), path);
+}
+
 
 unsigned char getFileType(const Path & path)
 {
@@ -389,12 +394,14 @@ void writeLine(int fd, string s)
 }
 
 
-static void _deletePath(const Path & path, unsigned long long & bytesFreed)
+static void _deletePath(int parentfd, const Path & path, unsigned long long & bytesFreed)
 {
     checkInterrupt();
 
+    string name(baseNameOf(path));
+
     struct stat st;
-    if (lstat(path.c_str(), &st) == -1) {
+    if (fstatat(parentfd, name.c_str(), &st, AT_SYMLINK_NOFOLLOW) == -1) {
         if (errno == ENOENT) return;
         throw SysError(format("getting status of '%1%'") % path);
     }
@@ -406,20 +413,45 @@ static void _deletePath(const Path & path, unsigned long long & bytesFreed)
         /* Make the directory accessible. */
         const auto PERM_MASK = S_IRUSR | S_IWUSR | S_IXUSR;
         if ((st.st_mode & PERM_MASK) != PERM_MASK) {
-            if (chmod(path.c_str(), st.st_mode | PERM_MASK) == -1)
+            if (fchmodat(parentfd, name.c_str(), st.st_mode | PERM_MASK, 0) == -1)
                 throw SysError(format("chmod '%1%'") % path);
         }
 
-        for (auto & i : readDirectory(path))
-            _deletePath(path + "/" + i.name, bytesFreed);
+        int fd = openat(parentfd, path.c_str(), O_RDONLY);
+        if (!fd)
+            throw SysError(format("opening directory '%1%'") % path);
+        AutoCloseDir dir(fdopendir(fd));
+        if (!dir)
+            throw SysError(format("opening directory '%1%'") % path);
+        for (auto & i : readDirectory(dir.get(), path))
+            _deletePath(dirfd(dir.get()), path + "/" + i.name, bytesFreed);
     }
 
-    if (remove(path.c_str()) == -1) {
+    int flags = S_ISDIR(st.st_mode) ? AT_REMOVEDIR : 0;
+    if (unlinkat(parentfd, name.c_str(), flags) == -1) {
         if (errno == ENOENT) return;
         throw SysError(format("cannot unlink '%1%'") % path);
     }
 }
 
+static void _deletePath(const Path & path, unsigned long long & bytesFreed)
+{
+    Path dir = dirOf(path);
+    if (dir == "")
+        dir = "/";
+
+    AutoCloseFD dirfd(open(dir.c_str(), O_RDONLY));
+    if (!dirfd) {
+        // This really shouldn't fail silently, but it's left this way
+        // for backwards compatibility.
+        if (errno == ENOENT) return;
+
+        throw SysError(format("opening directory '%1%'") % path);
+    }
+
+    _deletePath(dirfd.get(), path, bytesFreed);
+}
+
 
 void deletePath(const Path & path)
 {
diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index 1a2bb42a3..d62febaff 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -718,28 +718,39 @@ static void uninstallDerivations(Globals & globals, Strings & selectors,
     while (true) {
         string lockToken = optimisticLockProfile(profile);
 
-        DrvInfos installedElems = queryInstalled(*globals.state, profile);
-        DrvInfos newElems;
+        DrvInfos workingElems = queryInstalled(*globals.state, profile);
 
-        for (auto & i : installedElems) {
-            DrvName drvName(i.queryName());
-            bool found = false;
-            for (auto & j : selectors)
-                /* !!! the repeated calls to followLinksToStorePath()
-                   are expensive, should pre-compute them. */
-                if ((isPath(j) && globals.state->store->parseStorePath(i.queryOutPath()) == globals.state->store->followLinksToStorePath(j))
-                    || DrvName(j).matches(drvName))
-                {
-                    printInfo("uninstalling '%s'", i.queryName());
-                    found = true;
-                    break;
-                }
-            if (!found) newElems.push_back(i);
+        for (auto & selector : selectors) {
+            DrvInfos::iterator split = workingElems.begin();
+            if (isPath(selector)) {
+                StorePath selectorStorePath = globals.state->store->followLinksToStorePath(selector);
+                split = std::partition(
+                    workingElems.begin(), workingElems.end(),
+                    [&selectorStorePath, globals](auto &elem) {
+                        return selectorStorePath != globals.state->store->parseStorePath(elem.queryOutPath());
+                    }
+                );
+            } else {
+                DrvName selectorName(selector);
+                split = std::partition(
+                    workingElems.begin(), workingElems.end(),
+                    [&selectorName](auto &elem){
+                        DrvName elemName(elem.queryName());
+                        return !selectorName.matches(elemName);
+                    }
+                );
+            }
+            if (split == workingElems.end())
+                warn("selector '%s' matched no installed derivations", selector);
+            for (auto removedElem = split; removedElem != workingElems.end(); removedElem++) {
+                printInfo("uninstalling '%s'", removedElem->queryName());
+            }
+            workingElems.erase(split, workingElems.end());
         }
 
         if (globals.dryRun) return;
 
-        if (createUserEnv(*globals.state, newElems,
+        if (createUserEnv(*globals.state, workingElems,
                 profile, settings.envKeepDerivations, lockToken)) break;
     }
 }
diff --git a/src/nix/shell.cc b/src/nix/shell.cc
index 439ef02ed..b0710906b 100644
--- a/src/nix/shell.cc
+++ b/src/nix/shell.cc
@@ -205,13 +205,15 @@ struct Common : InstallableCommand, MixProfile
         }
     }
 
-    BuildEnvironment getBuildEnvironment(ref<Store> store)
+    std::pair<BuildEnvironment, std::string> getBuildEnvironment(ref<Store> store)
     {
         auto shellOutPath = getShellOutPath(store);
 
+        auto strPath = store->printStorePath(shellOutPath);
+
         updateProfile(shellOutPath);
 
-        return readEnvironment(store->printStorePath(shellOutPath));
+        return {readEnvironment(strPath), strPath};
     }
 };
 
@@ -262,7 +264,7 @@ struct CmdDevShell : Common, MixEnvironment
 
     void run(ref<Store> store) override
     {
-        auto buildEnvironment = getBuildEnvironment(store);
+        auto [buildEnvironment, gcroot] = getBuildEnvironment(store);
 
         auto [rcFileFd, rcFilePath] = createTempFile("nix-shell");
 
@@ -285,6 +287,8 @@ struct CmdDevShell : Common, MixEnvironment
         auto shell = getEnv("SHELL").value_or("bash");
 
         setEnviron();
+        // prevent garbage collection until shell exits
+        setenv("NIX_GCROOT", gcroot.data(), 1);
 
         auto args = Strings{std::string(baseNameOf(shell)), "--rcfile", rcFilePath};
 
@@ -316,7 +320,7 @@ struct CmdPrintDevEnv : Common
 
     void run(ref<Store> store) override
     {
-        auto buildEnvironment = getBuildEnvironment(store);
+        auto buildEnvironment = getBuildEnvironment(store).first;
 
         stopProgressBar();