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‎nix/installer.nix‎

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Original file line numberDiff line numberDiff line change
@@ -70,6 +70,7 @@
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imports = [
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./nix-settings.nix
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./un-pearl.nix
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];
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# Don't add nixpkgs to the image to save space, for our intended use case we don't need it

‎nix/setup-etc.c‎

Lines changed: 298 additions & 0 deletions
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <dirent.h>
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#include <pwd.h>
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#include <grp.h>
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#include <errno.h>
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#define MAX_PATH 4096
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#define STATIC_PATH "/etc/static"
14+
#define CLEAN_FILE "/etc/.clean"
15+
#define NIXOS_TAG "/etc/NIXOS"
16+
17+
int atomicSymlink(const char *source, const char *target) {
18+
char tmp[MAX_PATH];
19+
snprintf(tmp, MAX_PATH, "%s.tmp", target);
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unlink(tmp);
21+
if (symlink(source, tmp) != 0) {
22+
return 0;
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}
24+
if (rename(tmp, target) != 0) {
25+
unlink(tmp);
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return 0;
27+
}
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return 1;
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}
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int isStatic(const char *path) {
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char buf[MAX_PATH];
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struct stat st;
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if (lstat(path, &st) != 0) {
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return 0;
36+
}
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if (S_ISLNK(st.st_mode)) {
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ssize_t len = readlink(path, buf, MAX_PATH);
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if (len < 0 || len >= MAX_PATH) {
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return 0;
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}
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buf[len] = '\0';
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return strncmp(buf, STATIC_PATH "/", strlen(STATIC_PATH) + 1) == 0;
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}
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if (S_ISDIR(st.st_mode)) {
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DIR *dir = opendir(path);
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if (dir == NULL) {
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return 0;
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}
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struct dirent *entry;
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while ((entry = readdir(dir)) != NULL) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) {
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continue;
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}
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char subpath[MAX_PATH];
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snprintf(subpath, MAX_PATH, "%s/%s", path, entry->d_name);
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if (!isStatic(subpath)) {
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closedir(dir);
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return 0;
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}
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}
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closedir(dir);
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return 1;
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}
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return 0;
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}
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void cleanup(const char *path) {
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if (strcmp(path, "/etc/nixos") == 0) {
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return;
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}
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struct stat st;
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if (lstat(path, &st) != 0) {
74+
return;
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}
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if (S_ISLNK(st.st_mode)) {
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char buf[MAX_PATH];
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ssize_t len = readlink(path, buf, MAX_PATH);
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if (len < 0 || len >= MAX_PATH) {
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return;
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}
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buf[len] = '\0';
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if (strncmp(buf, STATIC_PATH "/", strlen(STATIC_PATH) + 1) == 0) {
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char target[MAX_PATH];
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snprintf(target, MAX_PATH, "%s/%s", STATIC_PATH, path + strlen("/etc/"));
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if (lstat(target, &st) != 0 || !S_ISLNK(st.st_mode)) {
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printf("removing obsolete symlink '%s'...\n", path);
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unlink(path);
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}
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}
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}
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}
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void createLink(const char *path, const char *etc_path) {
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char fn[MAX_PATH];
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snprintf(fn, MAX_PATH, "%s", path + strlen(etc_path) + 1);
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if (strcmp(fn, "resolv.conf") == 0 && getenv("IN_NIXOS_ENTER") != NULL) {
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return;
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}
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char target[MAX_PATH];
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snprintf(target, MAX_PATH, "/etc/%s", fn);
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char *dir = strdup(target);
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char *last_slash = strrchr(dir, '/');
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*last_slash = '\0';
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mkdir(dir, 0755);
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free(dir);
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char mode_path[MAX_PATH];
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snprintf(mode_path, MAX_PATH, "%s.mode", path);
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FILE *mode_file = fopen(mode_path, "r");
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if (mode_file != NULL) {
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char mode[16];
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if (fgets(mode, sizeof(mode), mode_file) != NULL) {
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mode[strcspn(mode, "\n")] = '\0';
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if (strcmp(mode, "direct-symlink") == 0) {
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char source[MAX_PATH];
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snprintf(source, MAX_PATH, "%s/%s", STATIC_PATH, fn);
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char link_target[MAX_PATH];
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ssize_t len = readlink(source, link_target, MAX_PATH);
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if (len < 0 || len >= MAX_PATH) {
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fprintf(stderr, "could not read symlink %s\n", source);
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} else {
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link_target[len] = '\0';
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if (!atomicSymlink(link_target, target)) {
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fprintf(stderr, "could not create symlink %s\n", target);
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}
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}
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} else {
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char uid_path[MAX_PATH];
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snprintf(uid_path, MAX_PATH, "%s.uid", path);
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FILE *uid_file = fopen(uid_path, "r");
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if (uid_file == NULL) {
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fprintf(stderr, "could not open %s\n", uid_path);
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fclose(mode_file);
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return;
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}
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char uid_str[32];
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if (fgets(uid_str, sizeof(uid_str), uid_file) == NULL) {
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fprintf(stderr, "could not read %s\n", uid_path);
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fclose(uid_file);
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fclose(mode_file);
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return;
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}
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uid_str[strcspn(uid_str, "\n")] = '\0';
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uid_t uid = uid_str[0] == '+' ? atoi(uid_str + 1) : getpwnam(uid_str) != NULL ? getpwnam(uid_str)->pw_uid : 0;
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fclose(uid_file);
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char gid_path[MAX_PATH];
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snprintf(gid_path, MAX_PATH, "%s.gid", path);
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FILE *gid_file = fopen(gid_path, "r");
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if (gid_file == NULL) {
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fprintf(stderr, "could not open %s\n", gid_path);
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fclose(mode_file);
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return;
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}
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char gid_str[32];
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if (fgets(gid_str, sizeof(gid_str), gid_file) == NULL) {
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fprintf(stderr, "could not read %s\n", gid_path);
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fclose(gid_file);
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fclose(mode_file);
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return;
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}
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gid_str[strcspn(gid_str, "\n")] = '\0';
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gid_t gid = gid_str[0] == '+' ? atoi(gid_str + 1) : getgrnam(gid_str) != NULL ? getgrnam(gid_str)->gr_gid : 0;
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fclose(gid_file);
168+
169+
char tmp_path[MAX_PATH];
170+
snprintf(tmp_path, MAX_PATH, "%s.tmp", target);
171+
char source[MAX_PATH];
172+
snprintf(source, MAX_PATH, "%s/%s", STATIC_PATH, fn);
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FILE *source_file = fopen(source, "rb");
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if (source_file == NULL) {
175+
fprintf(stderr, "could not open %s\n", source);
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fclose(mode_file);
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return;
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}
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FILE *tmp_file = fopen(tmp_path, "wb");
180+
if (tmp_file == NULL) {
181+
fprintf(stderr, "could not create %s\n", tmp_path);
182+
fclose(source_file);
183+
fclose(mode_file);
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return;
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}
186+
char buf[4096];
187+
size_t n;
188+
while ((n = fread(buf, 1, sizeof(buf), source_file)) > 0) {
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fwrite(buf, 1, n, tmp_file);
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}
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fclose(source_file);
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fclose(tmp_file);
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chmod(tmp_path, strtol(mode, NULL, 8));
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chown(tmp_path, uid, gid);
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if (rename(tmp_path, target) != 0) {
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fprintf(stderr, "could not create target %s\n", target);
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unlink(tmp_path);
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}
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}
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FILE *clean_file = fopen(CLEAN_FILE, "a");
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if (clean_file != NULL) {
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fprintf(clean_file, "%s\n", fn);
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fclose(clean_file);
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}
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}
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fclose(mode_file);
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} else {
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char source[MAX_PATH];
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snprintf(source, MAX_PATH, "%s/%s", STATIC_PATH, fn);
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if (!atomicSymlink(source, target)) {
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fprintf(stderr, "could not create symlink %s\n", target);
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}
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}
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}
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int main(int argc, char *argv[]) {
217+
if (argc != 2) {
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fprintf(stderr, "Usage: %s <etc-path>\n", argv[0]);
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return 1;
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}
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char *etc_path = argv[1];
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char static_path[MAX_PATH];
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snprintf(static_path, MAX_PATH, "%s", STATIC_PATH);
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226+
if (!atomicSymlink(etc_path, static_path)) {
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fprintf(stderr, "Failed to create symlink %s\n", static_path);
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return 1;
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}
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231+
DIR *dir = opendir("/etc");
232+
if (dir == NULL) {
233+
fprintf(stderr, "could not open /etc\n");
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return 1;
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}
236+
237+
struct dirent *entry;
238+
while ((entry = readdir(dir)) != NULL) {
239+
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) {
240+
continue;
241+
}
242+
char path[MAX_PATH];
243+
snprintf(path, MAX_PATH, "/etc/%s", entry->d_name);
244+
cleanup(path);
245+
}
246+
closedir(dir);
247+
248+
char *old_copied[4096];
249+
int old_copied_count = 0;
250+
FILE *clean_file = fopen(CLEAN_FILE, "r");
251+
if (clean_file != NULL) {
252+
char line[MAX_PATH];
253+
while (fgets(line, MAX_PATH, clean_file) != NULL) {
254+
line[strcspn(line, "\n")] = '\0';
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old_copied[old_copied_count++] = strdup(line);
256+
}
257+
fclose(clean_file);
258+
}
259+
260+
dir = opendir(etc_path);
261+
if (dir == NULL) {
262+
fprintf(stderr, "could not open %s\n", etc_path);
263+
return 1;
264+
}
265+
266+
while ((entry = readdir(dir)) != NULL) {
267+
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) {
268+
continue;
269+
}
270+
char path[MAX_PATH];
271+
snprintf(path, MAX_PATH, "%s/%s", etc_path, entry->d_name);
272+
createLink(path, etc_path);
273+
}
274+
closedir(dir);
275+
276+
clean_file = fopen(CLEAN_FILE, "w");
277+
if (clean_file != NULL) {
278+
for (int i = 0; i < old_copied_count; i++) {
279+
char path[MAX_PATH];
280+
snprintf(path, MAX_PATH, "/etc/%s", old_copied[i]);
281+
struct stat st;
282+
if (lstat(path, &st) == 0) {
283+
fprintf(clean_file, "%s\n", old_copied[i]);
284+
} else {
285+
printf("removing obsolete file '%s'...\n", path);
286+
}
287+
free(old_copied[i]);
288+
}
289+
fclose(clean_file);
290+
}
291+
292+
FILE *tag_file = fopen(NIXOS_TAG, "a");
293+
if (tag_file != NULL) {
294+
fclose(tag_file);
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}
296+
297+
return 0;
298+
}

‎nix/un-pearl.nix‎

Lines changed: 56 additions & 0 deletions
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# This module attempts to be a workaround to
2+
# remove the dependency of pearl from the
3+
# crictical path of using kexec images
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# in combination with nixos-anywhere
5+
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# THIS IS NOT FUNCTIONAL
7+
# POTENTIAL SAVING: ~80MB
8+
9+
# TODO:
10+
# - It's a proof of concept to calculate the saving (with nix-tree)
11+
# - I used some AI to get the initial transcript in bash and c
12+
# - If you, unlike me, know enough C please consider helping to finish the rewrite
13+
14+
{ config, lib, pkgs, utils, ... }: {
15+
nixpkgs.overlays = [
16+
(final: prev: {
17+
# avoid perl ~50MB - dummy
18+
syslinux = prev.coreutils;
19+
})
20+
];
21+
# avoid packages that depend on perl
22+
system.disableInstallerTools = true;
23+
system.switch.enable = false;
24+
# reimplement in c to avoid dependency on perl
25+
system.build.etcActivationCommands = let
26+
setup-etc = pkgs.writeCBin "setup-etc" (builtins.readFile ./setup-etc.c);
27+
etc = config.system.build.etc;
28+
in lib.mkForce
29+
''
30+
# Set up the statically computed bits of /etc.
31+
echo "setting up /etc..."
32+
${setup-etc}/bin/setup-etc ${etc}/etc
33+
'';
34+
system.activationScripts.users.text = let
35+
cfg = config.users;
36+
spec = pkgs.writeText "users-groups.json" (builtins.toJSON {
37+
inherit (cfg) mutableUsers;
38+
users = lib.mapAttrsToList (_: u:
39+
{ inherit (u)
40+
name uid group description home homeMode createHome isSystemUser
41+
password hashedPasswordFile hashedPassword
42+
autoSubUidGidRange subUidRanges subGidRanges
43+
initialPassword initialHashedPassword expires;
44+
shell = utils.toShellPath u.shell;
45+
}) cfg.users;
46+
groups = builtins.attrValues cfg.groups;
47+
});
48+
# update-users-groups = pkgs.writers.writeBashBin "update-users-groups" (builtins.readFile ./update-users-groups.sh);
49+
update-users-groups = pkgs.writeCBin "update-users-groups" (builtins.readFile ./update-users-groups.c);
50+
in lib.mkForce ''
51+
install -m 0700 -d /root
52+
install -m 0755 -d /home
53+
54+
${update-users-groups}/bin/update-users-groups ${spec}
55+
'';
56+
}

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