By mistake the file initrd.img-3.11.0-20-generic has been deleted in directory /boot. Now the system doesn't boot anymore.
Is there a possibility to restore initrd.img-3.11.0-20-generic?
Output of blkid from live-cd:
ubuntu@ubuntu:~$ sudo blkid 
/dev/loop0: TYPE="squashfs" 
/dev/sda1: UUID="999feae4-d45b-4cbf-8015-ef5d62d952cd" TYPE="ext2" 
/dev/sda5: UUID="9k5hUW-e2Hq-IfIN-08zV-jjDd-0mHm-CHySv4" TYPE="LVM2_member" 
/dev/sr0: LABEL="Ubuntu 14.04 LTS amd64" TYPE="iso9660" 
/dev/mapper/ubuntu--vg-root: UUID="8cf4d204-bbf8-44e2-a3e4-0f8c618e67ef" TYPE="ext4" 
/dev/mapper/ubuntu--vg-swap_1: UUID="6a0999af-2cee-453f-9a01-7c878df6213e" TYPE="swap"
Update 29.05.2014:
Here's what I've entered (following the recommendations of mniess) with the system responses:
ubuntu@ubuntu:~$ sudo -i
root@ubuntu:~# mount /dev/mapper/ubuntu--vg-root /mnt
root@ubuntu:~# mount /dev/sda1 /mnt/boot
root@ubuntu:~# for i in dev dev/pts proc sys sys/firmware; do mount --bind /$i /mnt/$i; done
root@ubuntu:~# cp /etc/resolv.conf /mnt/etc/resolv.conf
root@ubuntu:~# chroot /mnt
root@ubuntu:/# apt-get update
System response after command apt-get update:
Ign http://extras.ubuntu.com trusty InRelease
Ign http://security.ubuntu.com trusty-security InRelease     
Get:1 http://security.ubuntu.com trusty-security Release.gpg [933 B]
Get:2 http://extras.ubuntu.com trusty Release.gpg [72 B]
Ign http://de.archive.ubuntu.com trusty InRelease                                       
Get:3 http://security.ubuntu.com trusty-security Release [58.5 kB]
Hit http://extras.ubuntu.com trusty Release                                 
Ign http://de.archive.ubuntu.com trusty-updates InRelease                   
Ign http://de.archive.ubuntu.com trusty-backports InRelease                    
Ign http://de.archive.ubuntu.com trusty-proposed InRelease                     
Hit http://de.archive.ubuntu.com trusty Release.gpg                     
Hit http://extras.ubuntu.com trusty/main Sources
Get:4 http://security.ubuntu.com trusty-security/main Sources [16.0 kB]
Get:5 http://de.archive.ubuntu.com trusty-updates Release.gpg [933 B]        
Hit http://extras.ubuntu.com trusty/main amd64 Packages
Hit http://extras.ubuntu.com trusty/main i386 Packages                                     
Get:6 http://de.archive.ubuntu.com trusty-backports Release.gpg [933 B]
Get:7 http://security.ubuntu.com trusty-security/restricted Sources [14 B]
Get:8 http://security.ubuntu.com trusty-security/universe Sources [4,212 B]                
Get:9 http://de.archive.ubuntu.com trusty-proposed Release.gpg [933 B]                     
Get:10 http://security.ubuntu.com trusty-security/multiverse Sources [687 B]    
Hit http://de.archive.ubuntu.com trusty Release                                             
Get:11 http://security.ubuntu.com trusty-security/main amd64 Packages [51.8 kB]             
Get:12 http://de.archive.ubuntu.com trusty-updates Release [58.5 kB]                                  
Get:13 http://security.ubuntu.com trusty-security/restricted amd64 Packages [14 B]                     
Get:14 http://security.ubuntu.com trusty-security/universe amd64 Packages [17.9 kB]                    
Get:15 http://security.ubuntu.com trusty-security/multiverse amd64 Packages [1,154 B]                  
Get:16 http://de.archive.ubuntu.com trusty-backports Release [58.6 kB]                       
Get:17 http://security.ubuntu.com trusty-security/main i386 Packages [49.4 kB]
Get:18 http://security.ubuntu.com trusty-security/restricted i386 Packages [14 B]                       
Get:19 http://de.archive.ubuntu.com trusty-proposed Release [58.5 kB]       
Get:20 http://security.ubuntu.com trusty-security/universe i386 Packages [17.9 kB]
Get:21 http://security.ubuntu.com trusty-security/multiverse i386 Packages [1,404 B]                   
Hit http://de.archive.ubuntu.com trusty/main Sources                                         
Ign http://extras.ubuntu.com trusty/main Translation-en_US           
Hit http://de.archive.ubuntu.com trusty/restricted Sources
Hit http://de.archive.ubuntu.com trusty/universe Sources
Get:22 http://security.ubuntu.com trusty-security/main Translation-en [24.4 kB]
Hit http://de.archive.ubuntu.com trusty/multiverse Sources                           
Ign http://extras.ubuntu.com trusty/main Translation-en                                            
Hit http://de.archive.ubuntu.com trusty/main amd64 Packages          
Ign http://extras.ubuntu.com trusty/main Translation-de
Hit http://security.ubuntu.com trusty-security/multiverse Translation-en
Hit http://de.archive.ubuntu.com trusty/restricted amd64 Packages
Hit http://security.ubuntu.com trusty-security/restricted Translation-en
Hit http://de.archive.ubuntu.com trusty/universe amd64 Packages
Hit http://de.archive.ubuntu.com trusty/multiverse amd64 Packages
Get:23 http://security.ubuntu.com trusty-security/universe Translation-en [9,065 B]
Hit http://de.archive.ubuntu.com trusty/main i386 Packages                   
Hit http://de.archive.ubuntu.com trusty/restricted i386 Packages
Hit http://de.archive.ubuntu.com trusty/universe i386 Packages
Hit http://de.archive.ubuntu.com trusty/multiverse i386 Packages
Hit http://de.archive.ubuntu.com trusty/main Translation-en
Hit http://de.archive.ubuntu.com trusty/main Translation-de
Hit http://de.archive.ubuntu.com trusty/multiverse Translation-en
Hit http://de.archive.ubuntu.com trusty/multiverse Translation-de
Hit http://de.archive.ubuntu.com trusty/restricted Translation-en
Hit http://de.archive.ubuntu.com trusty/restricted Translation-de
Hit http://de.archive.ubuntu.com trusty/universe Translation-en
Hit http://de.archive.ubuntu.com trusty/universe Translation-de
Get:24 http://de.archive.ubuntu.com trusty-updates/main Sources [45.7 kB]
Get:25 http://de.archive.ubuntu.com trusty-updates/restricted Sources [14 B]
Get:26 http://de.archive.ubuntu.com trusty-updates/universe Sources [28.2 kB]
Ign http://security.ubuntu.com trusty-security/main Translation-en_US 
Get:27 http://de.archive.ubuntu.com trusty-updates/multiverse Sources [2,234 B]
Ign http://security.ubuntu.com trusty-security/main Translation-de    
Get:28 http://de.archive.ubuntu.com trusty-updates/main amd64 Packages [109 kB]
Ign http://security.ubuntu.com trusty-security/multiverse Translation-en_US
Ign http://security.ubuntu.com trusty-security/multiverse Translation-de
Get:29 http://de.archive.ubuntu.com trusty-updates/restricted amd64 Packages [14 B]
Ign http://security.ubuntu.com trusty-security/restricted Translation-en_US   
Get:30 http://de.archive.ubuntu.com trusty-updates/universe amd64 Packages [74.9 kB]
Ign http://security.ubuntu.com trusty-security/restricted Translation-de
Ign http://security.ubuntu.com trusty-security/universe Translation-en_US
Get:31 http://de.archive.ubuntu.com trusty-updates/multiverse amd64 Packages [7,089 B]
Ign http://security.ubuntu.com trusty-security/universe Translation-de 
Get:32 http://de.archive.ubuntu.com trusty-updates/main i386 Packages [107 kB]
Get:33 http://de.archive.ubuntu.com trusty-updates/restricted i386 Packages [14 B]
Get:34 http://de.archive.ubuntu.com trusty-updates/universe i386 Packages [75.3 kB]
Get:35 http://de.archive.ubuntu.com trusty-updates/multiverse i386 Packages [7,273 B]
Get:36 http://de.archive.ubuntu.com trusty-updates/main Translation-en [51.2 kB]
Hit http://de.archive.ubuntu.com trusty-updates/multiverse Translation-en
Hit http://de.archive.ubuntu.com trusty-updates/restricted Translation-en
Get:37 http://de.archive.ubuntu.com trusty-updates/universe Translation-en [33.8 kB]
Get:38 http://de.archive.ubuntu.com trusty-backports/main Sources [14 B]
Get:39 http://de.archive.ubuntu.com trusty-backports/restricted Sources [14 B]
Get:40 http://de.archive.ubuntu.com trusty-backports/universe Sources [4,123 B]
Get:41 http://de.archive.ubuntu.com trusty-backports/multiverse Sources [768 B]
Get:42 http://de.archive.ubuntu.com trusty-backports/main amd64 Packages [14 B]
Get:43 http://de.archive.ubuntu.com trusty-backports/restricted amd64 Packages [14 B]
Get:44 http://de.archive.ubuntu.com trusty-backports/universe amd64 Packages [4,099 B]
Get:45 http://de.archive.ubuntu.com trusty-backports/multiverse amd64 Packages [619 B]
Get:46 http://de.archive.ubuntu.com trusty-backports/main i386 Packages [14 B]
Get:47 http://de.archive.ubuntu.com trusty-backports/restricted i386 Packages [14 B]
Get:48 http://de.archive.ubuntu.com trusty-backports/universe i386 Packages [4,114 B]
Get:49 http://de.archive.ubuntu.com trusty-backports/multiverse i386 Packages [619 B]
Hit http://de.archive.ubuntu.com trusty-backports/main Translation-en
Get:50 http://de.archive.ubuntu.com trusty-backports/multiverse Translation-en [307 B]
Hit http://de.archive.ubuntu.com trusty-backports/restricted Translation-en
Get:51 http://de.archive.ubuntu.com trusty-backports/universe Translation-en [2,506 B]
Get:52 http://de.archive.ubuntu.com trusty-proposed/main amd64 Packages [88.4 kB]
Get:53 http://de.archive.ubuntu.com trusty-proposed/restricted amd64 Packages [14 B]
Get:54 http://de.archive.ubuntu.com trusty-proposed/multiverse amd64 Packages [14 B]
Get:55 http://de.archive.ubuntu.com trusty-proposed/universe amd64 Packages [16.6 kB]
Get:56 http://de.archive.ubuntu.com trusty-proposed/main i386 Packages [85.5 kB]
Get:57 http://de.archive.ubuntu.com trusty-proposed/restricted i386 Packages [14 B]
Get:58 http://de.archive.ubuntu.com trusty-proposed/multiverse i386 Packages [14 B]
Get:59 http://de.archive.ubuntu.com trusty-proposed/universe i386 Packages [16.7 kB]
Get:60 http://de.archive.ubuntu.com trusty-proposed/main Translation-en [40.7 kB]
Hit http://de.archive.ubuntu.com trusty-proposed/main Translation-de
Hit http://de.archive.ubuntu.com trusty-proposed/multiverse Translation-en
Hit http://de.archive.ubuntu.com trusty-proposed/multiverse Translation-de
Hit http://de.archive.ubuntu.com trusty-proposed/restricted Translation-en
Hit http://de.archive.ubuntu.com trusty-proposed/restricted Translation-de
Get:61 http://de.archive.ubuntu.com trusty-proposed/universe Translation-en [10.4 kB]
Hit http://de.archive.ubuntu.com trusty-proposed/universe Translation-de
Ign http://de.archive.ubuntu.com trusty/main Translation-en_US                                          
Ign http://de.archive.ubuntu.com trusty/multiverse Translation-en_US                                    
Ign http://de.archive.ubuntu.com trusty/restricted Translation-en_US                                    
Ign http://de.archive.ubuntu.com trusty/universe Translation-en_US                                      
Ign http://de.archive.ubuntu.com trusty-updates/main Translation-en_US                                  
Ign http://de.archive.ubuntu.com trusty-updates/main Translation-de                                     
Ign http://de.archive.ubuntu.com trusty-updates/multiverse Translation-en_US                            
Ign http://de.archive.ubuntu.com trusty-updates/multiverse Translation-de                               
Ign http://de.archive.ubuntu.com trusty-updates/restricted Translation-en_US                            
Ign http://de.archive.ubuntu.com trusty-updates/restricted Translation-de                               
Ign http://de.archive.ubuntu.com trusty-updates/universe Translation-en_US                              
Ign http://de.archive.ubuntu.com trusty-updates/universe Translation-de                                 
Ign http://de.archive.ubuntu.com trusty-backports/main Translation-en_US                                
Ign http://de.archive.ubuntu.com trusty-backports/main Translation-de                                   
Ign http://de.archive.ubuntu.com trusty-backports/multiverse Translation-en_US                          
Ign http://de.archive.ubuntu.com trusty-backports/multiverse Translation-de                             
Ign http://de.archive.ubuntu.com trusty-backports/restricted Translation-en_US                          
Ign http://de.archive.ubuntu.com trusty-backports/restricted Translation-de                             
Ign http://de.archive.ubuntu.com trusty-backports/universe Translation-en_US                            
Ign http://de.archive.ubuntu.com trusty-backports/universe Translation-de                               
Ign http://de.archive.ubuntu.com trusty-proposed/main Translation-en_US                                 
Ign http://de.archive.ubuntu.com trusty-proposed/multiverse Translation-en_US                           
Ign http://de.archive.ubuntu.com trusty-proposed/restricted Translation-en_US                           
Ign http://de.archive.ubuntu.com trusty-proposed/universe Translation-en_US                             
Fetched 1,250 kB in 8s (145 kB/s)                                                                       
Reading package lists... Done
root@ubuntu:/#
Then I've entered:
   root@ubuntu:/# apt-get --reinstall install linux-image-3.11.0-20-generic
...and got the following reply:
Reading package lists... Done
Building dependency tree      
Reading state information... Done
Reinstallation of linux-image-3.11.0-20-generic is not possible, it cannot be downloaded.
The following package was automatically installed and is no longer required:
  linux-image-generic
Use 'apt-get autoremove' to remove it.
0 upgraded, 0 newly installed, 0 to remove and 1674 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue [Y/n]? Y
Setting up icaclient (12.1.0) ...
/var/lib/dpkg/info/icaclient.postinst: 696: /var/lib/dpkg/info/icaclient.postinst: nspluginwrapper: not found
dpkg: error processing icaclient (--configure):
 subprocess installed post-installation script returned error exit status 2
Errors were encountered while processing:
 icaclient
E: Sub-process /usr/bin/dpkg returned an error code (1)
Next I've entered:
root@ubuntu:/# update-grub
System replied:
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.11.0-20-generic
Found linux image: /boot/vmlinuz-3.11.0-19-generic
Found linux image: /boot/vmlinuz-3.11.0-18-generic
Found linux image: /boot/vmlinuz-3.11.0-17-generic
Found linux image: /boot/vmlinuz-3.11.0-15-generic
Found linux image: /boot/vmlinuz-3.11.0-12-generic
Found memtest86+ image: /memtest86+.bin
done
Then I've entered:
root@ubuntu:/# grub-install
And got this:
Install device isn't specified.
Usage: grub-install [OPTION] [INSTALL_DEVICE]
Install GRUB on your drive.
  -h, --help              print this message and exit
  -v, --version           print the version information and exit
  --modules=MODULES       pre-load specified modules MODULES
  --boot-directory=DIR    install GRUB images under the directory DIR/grub
                          instead of the /boot/grub directory
  --target=TARGET         install GRUB for TARGET platform
                          [default=current]
  --directory=DIR         use GRUB images from DIR. Takes precedence
                          over target
  --grub-setup=FILE       use FILE as grub-setup
  --grub-mkimage=FILE     use FILE as grub-mkimage
  --grub-mkrelpath=FILE   use FILE as grub-mkrelpath
  --grub-probe=FILE       use FILE as grub-probe
  --allow-floppy          make the drive also bootable as floppy (default
                          for fdX devices). May break on some BIOSes.
  --recheck               delete device map if it already exists
  --force                 install even if problems are detected
  --force-file-id         use identifier file even if UUID is available
  --disk-module=MODULE    disk module to use (biosdisk or native). This
                          option is only available on BIOS target.
  --no-nvram              don't update the `boot-device' NVRAM
                          variable. This option is only available on
                          IEEE1275 targets.
  --removable             the installation device is removable. This option
                          is only available on EFI.
  --bootloader-id=ID      the ID of bootloader. This option is only
                      available on EFI.
  --efi-directory=DIR     use DIR as the EFI System Partition root.
  --uefi-secure-boot      install an image usable with UEFI Secure
                          Boot. This option is only available on EFI and if
                          the grub-efi-amd64-signed package is installed.
  --no-uefi-secure-boot   do not install an image usable with UEFI Secure
                          Boot, even if the system was currently started
                          using it. This option is only available on EFI.
INSTALL_DEVICE must be system device filename.
grub-install copies GRUB images into /boot/grub, and uses grub-setup
to install grub into the boot sector.
Report bugs to <bug-grub@gnu.org>.
As you can see above the procedure has shown some errors. The result is that the system still doesn't boot. Does someone have an idea about how to resolve the errors?
 
     
     
     
     
    