build: Make /etc/hosts a regular file again.

Commit 7c70a1080a0823fd3dd0f7ee83e5d7654ab6a872 ("gnu/system: Simplify the
creation of /etc (was: Turn /etc/localtime into a symlink)") made all of the
files under /etc other than sudoers symlinks to their store target.  This
causes a problem at least for the vpn-slice service, which expects to be able
to write to said file.

* gnu/build/activation.scm (activate-etc): Special-case /etc/hosts to make it
a regular file.

Change-Id: Ia42dacd8731edba5e72442ab0399bdc3f7101989
Signed-off-by: Maxim Cournoyer <maxim@guixotic.coop>
Modified-by: Maxim Cournoyer <maxim@guixotic.coop>
Fixes: #4800

1 files changed, 12 insertions, 7 deletions

diff --git a/gnu/build/activation.scm b/gnu/build/activation.scm
index f8a34b021c7..e2d1734367d 100644
--- a/gnu/build/activation.scm
+++ b/gnu/build/activation.scm
@@ -321,13 +321,18 @@ EINVAL, ELOOP, etc."
                     ;; convention to be followed.
                     (source (canonicalize-path* (string-append etc "/" file))))
                 (rm-f target)
-                (if (string=? (basename target) "sudoers")
-                    (begin
-                      ;; /etc/sudoers must be a regular file.
-                      (copy-file source target)
-                      ;; XXX: dirty hack to meet sudo's expectations
-                      (chmod target #o440))
-                    (symlink source target)))) ;usual case
+                (cond ((string=? (basename target) "sudoers")
+                       (begin
+                         ;; /etc/sudoers must be a regular file.
+                         (copy-file source target)
+                         ;; XXX: dirty hack to meet sudo's expectations
+                         (chmod target #o440)))
+                      ((string=? (basename target) "hosts")
+                       ;; /etc/hosts must be a regular file, as some software
+                       ;; like vpn-slice expect to be able to write to it.
+                       (copy-file source target))
+                      (else             ;usual case
+                       (symlink source target)))))
             (scandir etc (negate dot-or-dot-dot?)
                      ;; The default is 'string-locale<?', but we don't have
                      ;; it when run from the initrd's statically-linked