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shared/install: correctly install alias for units outside search path

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Currently, if a unit file is enabled from outside of the search path,
and that unit has an alias, then the symlink ends up pointing outside of
the search path too. For example:

 $ cat /tmp/a.service
 [Service]
 ExecStart=sleep infinity

 [Install]
 Alias=b.service
 WantedBy=multi-user.target

 $ systemctl enable /tmp/a.service
 Created symlink /etc/systemd/system/a.service → /tmp/a.service.
 Created symlink /etc/systemd/system/b.service → /tmp/a.service.
 Created symlink /etc/systemd/system/multi-user.target.wants/a.service → /tmp/a.service.

This then means the alias is treated as a separate unit:

 $ systemctl start a.service
 $ sudo systemctl status a
 ● a.service
  Loaded: loaded (/etc/systemd/system/a.service; enabled; preset: enabled)
  Active: active (running) since Fri 2024-03-15 15:17:49 EDT; 9s ago
 Main PID: 769593 (sleep)
   Tasks: 1 (limit: 18898)
  Memory: 220.0K
     CPU: 5ms
  CGroup: /system.slice/a.service
          └─769593 sleep infinity

 Mar 15 15:17:49 six systemd[1]: Started a.service.
 $ sudo systemctl status b
 ○ b.service
  Loaded: loaded (/etc/systemd/system/b.service; alias)
  Active: inactive (dead)

To fix this, make sure the alias uses a target that is inside the search
path. Since the unit file itself is outside of the search path, a
symlink inside the search path will have been created already. Hence,
just point the alias symlink to that recently created symlink.
This commit is contained in:
Nick Rosbrook
2024-03-18 11:58:07 +00:00
committed by Luca Boccassi
parent ce88017255
commit 6fec0fed10
3 changed files with 35 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/shared/install.c
+14 -2
View File
@@ -1941,7 +1941,7 @@ static int install_info_symlink_alias(
assert(config_path);
STRV_FOREACH(s, info->aliases) {
_cleanup_free_ char *alias_path = NULL, *dst = NULL, *dst_updated = NULL;
_cleanup_free_ char *alias_path = NULL, *alias_target = NULL, *dst = NULL, *dst_updated = NULL;
r = install_name_printf(scope, info, *s, &dst);
if (r < 0) {
@@ -1960,6 +1960,18 @@ static int install_info_symlink_alias(
if (!alias_path)
return -ENOMEM;
r = in_search_path(lp, info->path);
if (r < 0)
return r;
if (r == 0) {
/* The unit path itself is outside of the search path. To
* correctly apply the alias, we need the alias symlink to
* point to the symlink that was created in the search path. */
alias_target = path_join(config_path, info->name);
if (!alias_target)
return -ENOMEM;
}
bool broken;
r = chase(alias_path, lp->root_dir, CHASE_NONEXISTENT, /* ret_path = */ NULL, /* ret_fd = */ NULL);
if (r < 0 && r != -ENOENT) {
@@ -1968,7 +1980,7 @@ static int install_info_symlink_alias(
}
broken = r == 0; /* symlink target does not exist? */
RET_GATHER(ret, create_symlink(lp, info->path, alias_path, force || broken, changes, n_changes));
RET_GATHER(ret, create_symlink(lp, alias_target ?: info->path, alias_path, force || broken, changes, n_changes));
}
return ret;