purging old kernels fails to remove old initrd files

Solution 1:

It is safe to remove them manually. It also looks like there is a bug report filed: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=717584

I can report the same happening here with the 3.13.0-54 kernel and 3.13.0-55 kernel.

-rw-r--r-- 1 root root 1.2M Jun 17 20:03 abi-3.13.0-55-generic
-rw-r--r-- 1 root root 1.2M Jun 19 05:04 abi-3.13.0-57-generic
-rw-r--r-- 1 root root 162K Jun 17 20:03 config-3.13.0-55-generic
-rw-r--r-- 1 root root 162K Jun 19 05:04 config-3.13.0-57-generic
drwxr-xr-x 5 root root  12K Jul 11 15:54 grub
-rw-r--r-- 1 root root  11M Jul  7 21:37 initrd.img-3.13.0-54-generic.old-dkms
-rw-r--r-- 1 root root  27M Jul  4 13:37 initrd.img-3.13.0-55-generic
-rw-r--r-- 1 root root  27M Jul  4 13:37 initrd.img-3.13.0-55-generic.old-dkms
-rw-r--r-- 1 root root  27M Jul  6 18:28 initrd.img-3.13.0-57-generic
-rw-r--r-- 1 root root 173K Mar 12  2014 memtest86+.bin
-rw-r--r-- 1 root root 174K Mar 12  2014 memtest86+.elf
-rw-r--r-- 1 root root 175K Mar 12  2014 memtest86+_multiboot.bin
-rw------- 1 root root 3.3M Jun 17 20:03 System.map-3.13.0-55-generic
-rw------- 1 root root 3.3M Jun 19 05:04 System.map-3.13.0-57-generic
-rw------- 1 root root 5.6M Jun 17 20:03 vmlinuz-3.13.0-55-generic
-rw------- 1 root root 5.6M Jun 19 05:04 vmlinuz-3.13.0-57-generic

Solution 2:

You could run the command rm /boot/*.old-dkms with Root privileges. However, be sure that the removed *.old-dkms files are not needed by older kernels that you may have installed. You can see a list of your currently installed kernels by executing dpkg-query -l "linux-image-[0-9]*" | grep -e "^ii".