[PATCH initramfs-tools 7/9] Support requesting automatic selection of resume device with RESUME=auto

[Ben Hutchings]

For now, this is effectively the same as setting RESUME to empty or
not setting it.

Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 hooks/resume     | 25 ++++++++++++++-----------
 initramfs.conf.5 |  3 ++-
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/hooks/resume b/hooks/resume
index 3e3f6dbbc3b6..43eb146b1f42 100755
--- a/hooks/resume
+++ b/hooks/resume
@@ -16,7 +16,7 @@ prereqs)
 esac
 
 # First check if a location is set and is a valid swap partition
-if [ -n "$RESUME" ] && \
+if [ -n "$RESUME" ] && [ "$RESUME" != auto ] && \
    { [ "$RESUME" = none ] || blkid -p -n swap $RESUME >/dev/null 2>&1; }; then
        # As mkinitramfs copies the config file nothing to do.
        exit 0
@@ -24,16 +24,19 @@ fi
 
 # We need to be able to read the listed swap partitions
 if ischroot || [ ! -r /proc/swaps ]; then
-       exit 0
+       resume_auto=
+else
+       # Try to autodetect the RESUME partition, using biggest swap?
+       resume_auto=$(grep ^/dev/ /proc/swaps | sort -rnk3 | head -n 1 | cut -d 
" " -f 1)
+       if [ -n "$resume_auto" ]; then
+               UUID=$(blkid -s UUID -o value "$resume_auto" || true)
+               if [ -n "$UUID" ]; then
+                       resume_auto="UUID=$UUID"
+               fi
+       fi
 fi
 
-# Try to autodetect the RESUME partition, using biggest swap?
-# Write detected resume to intramfs conf.d
-RESUME=$(grep ^/dev/ /proc/swaps | sort -rnk3 | head -n 1 | cut -d " " -f 1)
-if [ -n "$RESUME" ]; then
-       UUID=$(blkid -s UUID -o value "$RESUME" || true)
-       if [ -n "$UUID" ]; then
-                       RESUME="UUID=$UUID"
-       fi
-       echo "RESUME=${RESUME}" > ${DESTDIR}/conf/conf.d/zz-resume-auto
+# Write selected resume device to intramfs conf.d
+if [ "$RESUME" = auto ] || [ -n "$resume_auto" ]; then
+       echo "RESUME=${resume_auto}" > ${DESTDIR}/conf/conf.d/zz-resume-auto
 fi
diff --git a/initramfs.conf.5 b/initramfs.conf.5
index c0d778ca1928..b4eea705016f 100644
--- a/initramfs.conf.5
+++ b/initramfs.conf.5
@@ -78,7 +78,8 @@ Set to \fInfs\fP for an NFS root share.
 .TP
 \fB RESUME
 Specifies the device used for suspend-to-disk (hibernation), which the
-initramfs code should attempt to resume from.  If this is not defined,
+initramfs code should attempt to resume from.  If this is not defined
+or is set to \fIauto\fP,
 .B mkinitramfs
 will automatically select the largest available swap partition.
 Set it to \fInone\fP to disable resume from disk.

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