Whatever distro you're using, tell it to remove old kernel files.

   uname -a

will tell you the currenct version - don't remove that.

Most likely you can remove all versions prior to 3.19.0-47

On Wed, 20 Jan 2016, admin at lctn.org wrote:

> I'm getting disk monitor alerts on /boot. How can I determine which files
> are safe to remove?
> 
> -rw-r--r-- 1 root root  1271765 Jan 18 12:05 abi-3.19.0-47-generic
> -rw-r--r-- 1 root root   177779 Jul 24 18:19 config-3.19.0-25-generic
> -rw-r--r-- 1 root root   177790 Dec  2 05:19 config-3.19.0-39-generic
> -rw-r--r-- 1 root root   177808 Dec  8 13:32 config-3.19.0-41-generic
> -rw-r--r-- 1 root root   177808 Dec 18 06:36 config-3.19.0-42-generic
> -rw-r--r-- 1 root root   177808 Dec 31 11:40 config-3.19.0-43-generic
> -rw-r--r-- 1 root root   177808 Jan 18 12:05 config-3.19.0-47-generic
> drwxr-xr-x 5 root root     1024 Jan 20 06:48 grub
> -rw-r--r-- 1 root root 20752348 Dec  7 11:43 initrd.img-3.19.0-25-generic
> -rw-r--r-- 1 root root 20759486 Dec  8 06:44 initrd.img-3.19.0-39-generic
> -rw-r--r-- 1 root root 20759188 Dec 17 07:01 initrd.img-3.19.0-41-generic
> -rw-r--r-- 1 root root 20758251 Dec 19 06:35 initrd.img-3.19.0-42-generic
> -rw-r--r-- 1 root root 20761822 Jan  6 06:53 initrd.img-3.19.0-43-generic
> -rw-r--r-- 1 root root 20761010 Jan 20 06:48 initrd.img-3.19.0-47-generic
> drwx------ 2 root root    12288 Dec  7 11:36 lost+found
> -rw-r--r-- 1 root root   176500 Mar 12  2014 memtest86+.bin
> -rw-r--r-- 1 root root   178176 Mar 12  2014 memtest86+.elf
> -rw-r--r-- 1 root root   178680 Mar 12  2014 memtest86+_multiboot.bin
> -rw------- 1 root root  3623533 Jul 24 18:19 System.map-3.19.0-25-generic
> -rw------- 1 root root  3628776 Dec  2 05:19 System.map-3.19.0-39-generic
> -rw------- 1 root root  3628871 Dec  8 13:32 System.map-3.19.0-41-generic
> -rw------- 1 root root  3628871 Dec 18 06:36 System.map-3.19.0-42-generic
> -rw------- 1 root root  3628871 Dec 31 11:40 System.map-3.19.0-43-generic
> -rw------- 1 root root  3628871 Jan 18 12:05 System.map-3.19.0-47-generic
> -rw------- 1 root root  6565968 Jul 24 18:19 vmlinuz-3.19.0-25-generic
> -rw------- 1 root root  6571728 Dec  2 05:19 vmlinuz-3.19.0-39-generic
> -rw------- 1 root root  6571728 Dec  8 13:32 vmlinuz-3.19.0-41-generic
> -rw------- 1 root root  6571600 Dec 18 06:36 vmlinuz-3.19.0-42-generic
> -rw------- 1 root root  6571600 Dec 31 11:40 vmlinuz-3.19.0-43-generic
> -rw------- 1 root root  6571600 Jan 18 12:05 vmlinuz-3.19.0-47-generic
> 
>