fstab-generator: make error more helpful in case of duplicates in fstab

Traditional sysvinit systems would not complain about duplicates in
fstab. Rather it (through monut -a) would mount one fs on top of another,
in effect the last entry taking precedent.

In systemd, the first entry takes precedent, all subsequent ones are
ignored and an error is printed.

The change of behavior and the source of this error message was causing
some confusion, so give a hint what migt be wrong.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/fstab-generator/fstab-generator.c b/src/fstab-generator/fstab-generator.c
index 7b3bf11ed..ba55f2c2b 100644
--- a/src/fstab-generator/fstab-generator.c
+++ b/src/fstab-generator/fstab-generator.c
@@ -111,7 +111,10 @@ static int add_swap(const char *what, struct mntent *me) {
         f = fopen(unit, "wxe");
         if (!f) {
                 r = -errno;
-                log_error("Failed to create unit file %s: %m", unit);
+                if (errno == EEXIST)
+                        log_error("Failed to create swap unit file %s, as it already exists. Duplicate entry in /etc/fstab?", unit);
+                else
+                        log_error("Failed to create unit file %s: %m", unit);
                 goto finish;
         }
 
@@ -254,7 +257,10 @@ static int add_mount(const char *what, const char *where, struct mntent *me) {
         f = fopen(unit, "wxe");
         if (!f) {
                 r = -errno;
-                log_error("Failed to create unit file %s: %m", unit);
+                if (errno == EEXIST)
+                        log_error("Failed to create mount unit file %s, as it already exists. Duplicate entry in /etc/fstab?", unit);
+                else
+                        log_error("Failed to create unit file %s: %m", unit);
                 goto finish;
         }