RFC: feat(livenet): add memory size check depending on live image size

man/dracut.cmdline.7.asc

@@ -1117,6 +1117,13 @@ NOTE: There must be enough free RAM available to hold the complete image.
 +
 This method is very suitable for diskless boots.
 
+**rd.minmem=**__<megabyte>__::
+Specify minimum free RAM in MB after copying a live disk image into memory.
+The default is 1024.
++
+This parameter only applies together with the parameters rd.writable.fsimg
+or rd.live.ram.
+
 **root=**live:__<url>__::
 Boots a live image retrieved from __<url>__.  Requires the dracut 'livenet'
 module.  Valid handlers: __http, https, ftp, torrent, tftp__.

modules.d/90dmsquash-live/dmsquash-live-root.sh

@@ -314,6 +314,8 @@ if [ -e /run/initramfs/live/${live_dir}/${squash_image} ]; then
 fi
 if [ -e "$SQUASHED" ]; then
     if [ -n "$live_ram" ]; then
+        imgsize=$(($(stat -c %s -- $SQUASHED) / (1024 * 1024)))
+        check_live_ram $imgsize
         echo 'Copying live image to RAM...' > /dev/kmsg
         echo ' (this may take a minute)' > /dev/kmsg
         dd if=$SQUASHED of=/run/initramfs/squashed.img bs=512 2> /dev/null

modules.d/90livenet/livenetroot.sh

@@ -16,6 +16,13 @@ netroot="$2"
 liveurl="${netroot#livenet:}"
 info "fetching $liveurl"
 
+if getargbool 0 'rd.writable.fsimg'; then
+
+    imgsize=$(($(curl -sIL "$liveurl" | sed -n 's/Content-Length: *\([[:digit:]]*\).*/\1/p') / (1024 * 1024)))
+
+    check_live_ram $imgsize
+fi
+
 imgfile=
 #retry until the imgfile is populated with data or the max retries
 i=1

modules.d/99base/dracut-lib.sh

@@ -1151,3 +1151,28 @@ load_fstype() {
     done < /proc/filesystems
     modprobe "$1"
 }
+
+# parameter: size of live image
+# calls emergency shell if ram size is too small for the image
+check_live_ram() {
+    minmem=$(getarg rd.minmem)
+    minmem=${minmem:-1024}
+    imgsize=$1
+    memsize=$(($(sed -n 's/MemTotal: *\([[:digit:]]*\).*/\1/p' /proc/meminfo) / 1024))
+
+    if [ -z "$imgsize" ]; then
+        warn "Image size could not be determined"
+        return 0
+    fi
+
+    if [ $((memsize - imgsize)) -lt "$minmem" ]; then
+        sed -i "N;/and attach it to a bug report./s/echo$/echo\n\
+         echo \n\
+         echo 'Warning!!!'\n\
+         echo 'The memory size of your system is too small for this live image.'\n\
+         echo 'Expect killed processes due to out of memory conditions.'\n\
+         echo \n/" /usr/bin/dracut-emergency
+
+        emergency_shell
+    fi
+}