I had the same problem when using an encrypted swap partition. Neither the general Swap FAQ, Puny Geek's solution to the "cryptswap1 is not ready yet or not present" message nor Braiam's answer to this question solved the problem for me - sometimes the swap was available, sometimes it wasn't. After many reboots and some poking around, I think I have found the underlying reason:
The path to the swap partition like /dev/sda3 is sometimes different, e.g. /dev/sdb3. Since the file /etc/crypttab by default seems to identify the swap partition through this path, sometimes it would find it (if that partition happens to get the same path at boot) or not (if the partition gets a different path assigned at boot).
Seems like I wasn't the only one with that problem becasue as described here, a better solution would be to bind the swap partition through it's drive ID instead of its /dev/sd* path. This can be found by running
ls -l /dev/disk/by-id/
which lists the disk IDs for all partitions including the swap, which in my case was
ata-TOSHIBA_MQ01UBD100_73JATD5GT-part3 -> ../../sdb3
Double check in a program like Disk Utility that the -> ../../sdb* part of this line is indeed the partition you intend to use for swapping, as this (as I said before) can sometimes change names. As always, keep this in mind:
Caution: fiddling with cryptsetup and disk devices is dangerous for
data and OS. I personally made a full backup on a separate disk and
then umplugged it to be sure it wouldn’t be involved in any mishap.
Then edit your /etc/crypttab file by using the ID link instead of the "raw" path, in my case this line is
cryptswap1 /dev/disk/by-id/ata-TOSHIBA_MQ01UBD100_73JATD5GT-part3 /dev/urandom swap,cipher=aes-cbc-essiv:sha256
I think this method should be the default for new installations, as one apparently can never be sure of the /dev/sd* paths... which I find somewhat worrying as I have the feeling that there are way more scripts and software out there which still rely on these paths (instead of IDs, labels or UUIDs) to stay the same across reboots.
TODO:
I haven't checked if resuming out of hibernation still works with this setup, as this seems to rely on a UUID (which my swap partition didn't have), as stated on this page: https://altinukshini.wordpress.com/2012/10/15/devmappercryptswap1-is-not-ready-yet-or-not-present/
Update:
Hibernation seems to work fine so far. Hope this solves these problems for others as well!
Best Answer
This error message indicates that the the system was unable to use its encrypted swap partition.
Not being able to use swap may cause slowdown, especially if your machine doesn't have much RAM installed.
Assuming the system is booting, you should be able to fix the problem without too much hassle.
If this is happening when you boot the CD/DVD or USB flash drive to install Ubuntu, then assuming installation is still working, it can be ignored. Your installed system might or might not have the same problem once created--if it does, the problem can be addressed in the installed system.
If this is happening on a system that is installed on your hard disk, then your system might still run okay, but it's a good idea to fix it--if you have a swap partition (or swap file), you may as well use it.
Most Ubuntu systems with swap have a swap partition. Assuming that is the case, the technique described in this blog post may help:
Here's a summary, with some additional information that may be helpful for novices, and in my own words. I suggest taking a look at that post as well though (assuming it remains accessible), as it contains some examples and other information that I've left out for brevity.
sudo swapoff -a/etc/crypttab(e.g.,sudo nano -w /etc/crypttaborsudo -H gedit /etc/cryptabfor a GUI editor) and put a#at the beginning of the line that starts withcryptswap1. Save the file./dev/mapper/cryptswap1in/etc/fstab.linux-swap. Make sure to get the right partition; if you get the wrong one, you'll lose possibly important data! The line you commented out incrypttabshould give the correct partition name (it comes right after/dev/).sudo mkswap /dev/..., repacing...with that same device name. Part of that command's output should be text that saysUUID=.....where.....is a string of letters and numbers./etc/initramfs-tools/conf.d/resume, find the line that saysRESUME=UUID=followed by letters and numbers like (but not identical to).....from the last step. Replace them with.....(i.e., with the letters and numbersmkswapgave afterUUID=.sudo swapon /dev/...(with the same/dev/...as you had in steps 4 and 5 above).sudo ecryptfs-setup-swap.swapon -swill check to see if swap is successfully enabled. See that blog post for more information, and example output, for checking this.Source: http://punygeek.blogspot.com/2012/10/ubuntu-1204-how-to-solve-disk-drive-for.html (on http://punygeek.blogspot.com/) by Litmus / Puny Geek. Some commands are copied; prose is not copied, but often expresses the same ideas.
Finally, note that this might be a bug. (I believe multiple factors could cause this problem, only some of which are bugs.) In particular, it resembles Launchpad Bug #1153661. If you believe that's your situation, you might want to subscribe to that, mark yourself affected (with the green "This bug affects..." link at the top of the page), and if you have any additional information to provide, comment with it.