Comment 28 for bug 1453738

Notes for myself, please ignore.

This resets what ecryptfs-setup-swap does and re-runs it, for testing a fixed version:

sudo sed -i '/cryptswap/d' /etc/fstab /etc/crypttab && sudo sh -ex /usr/bin/ecryptfs-setup-swap --force; echo "---- fstab ---"; grep swap /etc/fstab; echo "--- crypttab ----"; cat /etc/crypttab; echo "--- swap stat ---"; swapon -s

The problem is in the loop that tries to comment out existing swap from /etc/fstab: It only checks for UUID= and the resolved name like /dev/dm-1, but it does not take any symlinks like "/dev/mapper/ubuntu--vg-swap_1 -> ../dm-1" into account.

This can be fixed with

--- /usr/bin/ecryptfs-setup-swap 2015-03-28 01:37:38.000000000 +0100
+++ ecryptfs-setup-swap 2015-07-09 08:51:38.554860202 +0200
@@ -149,7 +149,9 @@
 for swap in $swaps; do
  info `gettext "Setting up swap:"` "[$swap]"
  uuid=$(blkid -o value -s UUID $swap)
- for target in "UUID=$uuid" $swap; do
+ # /etc/fstab might use a symlink like /dev/mapper/ubuntu--vg-swap_1
+ links=$(for d in $(udevadm info --query=symlink -n /dev/dm-1); do echo /dev/$d; done)
+ for target in "UUID=$uuid" $swap $links; do
   if [ -n "$target" ] && grep -qs "^$target\s\+" /etc/fstab; then
    sed -i "s:^$target\s\+:\#$target :" /etc/fstab
    warn "Commented out your unencrypted swap from /etc/fstab"

This then produces

---- fstab ---
#/dev/mapper/ubuntu--vg-swap_1 none swap sw 0 0
/dev/mapper/cryptswap1 none swap sw 0 0
--- crypttab ----
cryptswap1 UUID=ddec94de-8a98-4e95-bf76-a01e79029f35 /dev/urandom swap,offset=1024,cipher=aes-xts-plain64

which works fine:

lrwxrwxrwx 1 root root 7 Jul 9 08:55 /dev/mapper/cryptswap1 -> ../dm-2

$ sudo swapon -s
Filename Type Size Used Priority
/dev/dm-2 partition 2096636 0 -1

Now we need to clean this up on upgrades. The trick there is to avoid reintroducing bug 953875, from installations which don't have the "offset=" in crypttab.