Can i remove /initrd.img and /vmlinuz in root?

If you haven't seen them before, it's because you never looked.

– @deadflowr on "vmlinuz and initrd.img symbolic links in / directory" at Ubuntu Forums

The /vmlinuz and /initrd.img symlinks point to the latest compressed Linux kernel executable and initial RAM disk, respectively, and their *.old counterparts are the symlinks to the preceeding version. If you dig around in your GRUB configuration (found at /boot/grub/grub.cfg), you will find that there is no reference to /vmlinuz or /initrd.img, rather the original file. 

menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-2290c2ad-8832-4d80-a82d-e966d73c23e9' {
    recordfail
    load_video
    gfxmode $linux_gfx_mode
    insmod gzio
    if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
    insmod part_gpt
    insmod ext2
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root  2290c2ad-8832-4d80-a82d-e966d73c23e9
    else
      search --no-floppy --fs-uuid --set=root 2290c2ad-8832-4d80-a82d-e966d73c23e9
    fi
    linux   /boot/vmlinuz-4.15.0-23-generic root=UUID=2290c2ad-8832-4d80-a82d-e966d73c23e9 ro  console=tty1 console=ttyS0
    initrd  /boot/initrd.img-4.15.0-23-generic
}

Output of ls -l / provided for context.

lrwxrwxrwx   1 root root    33 Jun 20 06:57 initrd.img -> boot/initrd.img-4.15.0-23-generic
lrwxrwxrwx   1 root root    33 May 22 10:54 initrd.img.old -> boot/initrd.img-4.15.0-22-generic
...
lrwxrwxrwx   1 root root    30 Jun 20 06:57 vmlinuz -> boot/vmlinuz-4.15.0-23-generic
lrwxrwxrwx   1 root root    30 May 22 10:54 vmlinuz.old -> boot/vmlinuz-4.15.0-22-generic

Because your grub.cfg is auto-updated with each kernel release, it is much safer to reference the actual file than a symlink (in case it is deleted or changed). But if you are doing some of your own modifications to the grub.cfg (not recommended because they might get overwritten), /vmlinuz or /initrd.img can be used to your convenience as a link to the latest kernel images.

Is it safe to delete them? Yeah, but they will get recreated when/if you update your kernel (using apt upgrade) or update your GRUB (update-grub).

Read more

  • "vmlinuz and initrd.img symbolic links in / directory" at Ubuntu Forums
  • "Anatomy of the initrd and vmlinuz" by Munshi Hafizul Haque of IBM

If you look (with file etc) you'll probably notice they are symbolic links.

Should your system not boot (and you end up in grub-recovery) they are really handy to have your system boot as you don't have to remember, or go looking to see the full path & filename for the kernel & initial.ramdisk for either your current [latest] or prior [old] kernel. I may not use them often, but I consider them very handy.

A file /vm* on my box showed 

guiverc@d960-ubu2:~$   file /vm* 
/vmlinuz:     symbolic link to boot/vmlinuz-4.15.0-23-generic
/vmlinuz.old: symbolic link to boot/vmlinuz-4.15.0-22-generic

guiverc@d960-ubu2:~$   uname -r
4.15.0-23-generic

being my current & prior kernels. Removing them won't give me any more disk space (as they are only directory entries; links to the real file in boot/).

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