Accidentally removed /bin. How do I restore it?
Is it possible?
Well, most trivial and important utilities are installed in /bin
, and now you lost access to all of them. In fact, if you reboot, your system will not be able to boot-up anymore.
Anyway, we are going to fix the issue and make /bin
's contents as close as is possible to where it was. The only difference would be some symbolic links which we will fix too.
How?
First, we should chroot
into your broken system, but with a minor difference! After that we will get a list of installed packages on your system which have any installed file in /bin
directory, then we are going to only download the needed packages and extract the necessary files into /bin
. Then we'll be done.
For example, after chroot
, we can get a list of packages which have installed files in /bin
using:
dpkg --search /bin | cut -f1 -d: | tr ',' '\n'
And we can also use:
dpkg --listfiles PACKAGE-NAME | grep "^/bin/" # or awk '$0 ~ "^/bin/
to list installed files by these packages in /bin
.
Then we simply create a list of all packages that are necessary to us, then download them and extract them to /bin
with something like:
xargs apt download < list-packages
dpkg-deb -x PACKAGE .
mv ./bin/* /bin
However we must use a script to check all installed packages on our system, because doing it manually is just madness.
So I wrote a script which does everything we need. It finds all necessary packages for us to restore /bin
, shows us the name of each package and their related files that belongs to /bin
. Here is a screenshot:
At the end we choose to reinstall all packages or only download and extract the necessary files to /bin
(which is the recommended option):
You can grab a copy of this script or download it directly.
Lets start
chroot
Boot your system with a live disk which has same architecture as your installed Ubuntu, open a terminal and get root access:
sudo -i
Mount your root
file system (for me it's /dev/sda1
):
mount /dev/sda1 /mnt
We will need connectivity to the Internet, so copy resolv.conf
from live Ubuntu to your mounted root partition:
cp /etc/resolv.conf /mnt/etc/resolv.conf
Now copy the script to somewhere on the mounted partition, e.g:
cp /media/ubuntu/usb/restore-bin.sh /mnt/restore-bin.sh
or you can download it using wget
, etc. like:
wget https://git.io/v9fRm -O /mnt/restore-bin.sh
Mount other necessary paths:
mount --bind /dev /mnt/dev
mount --bind /sys /mnt/sys
mount -t proc /proc /mnt/proc
And here is the minor difference: how can we chroot
to a broken system when there is no /bin
directory in there? Which shell should we run?
So create a temporary bin directory. e.g: named bintmp
within your broken system root:
mkdir /mnt/bintmp
Then bind the live /bin
into that:
mount --bind /bin /mnt/bintmp
Chroot into the system while setting the /bintmp/bash
as your login shell:
chroot /mnt /bintmp/bash
Export the /bintmp
as your PATH
environment variable:
export PATH=/bintmp:$PATH
Give the script the executable bit:
chmod +x restore-bin.sh
Run the script:
./restore-bin.sh
Wait for the search to be completed then answer the question we saw in the screenshot. It will start to restore the /bin
and we are almost done.
After it's done, use CTRL+D to get out of chroot
environment and unmount the mounted paths:
umount -R /mnt
Reboot the system.
Restoring the links within /bin
Now almost all of files within /bin
directory are back, except around 5 symbolic links which are managed by update-alternatives
.
In your running system, run:
sudo update-alternatives --all
It asks you some questions; you can simply press ENTER to accept them all.
And now we are done.
If your current system still has a running shell and internet access, this can be done using tools existing elsewhere on the system. I'm assuming you only deleted /bin
. /bin
of course has the most convenient utility that you could use in such a situation (busybox), but without that, we'll have to get a little creative.
Since you already have a running shell, and since sudo
is in /usr/bin
, let's get ourselves a running root shell before we do further damage. But /bin/bash
and most other shells are gone! Luckily, Linux still has an in-memory copy of the shell you're using. So:
sudo /proc/$$/exe
Strictly speaking we don't need a root shell for much of what follows. But anyway.
Now, dpkg
still works, at least for finding which packages have files in /bin
:
dpkg -S /bin
We can use awk
to process it and get the package names, and xargs
and apt-get
to download the packages (all in /usr/bin
). If you have a temporary directory that you can use, cd
there, because your current directory is going to get a bit messy:
dpkg -S /bin | awk -F '[, :]' '{NF--}1' | xargs apt-get download
Now, the biggest problem we have is that /bin/tar
is missing, and without it, dpkg
can't extract the archives. We can get two-thirds of the way there, because:
.deb
files are actuallyar
archives (again in/usr/bin
):ar x tar_*.deb
Consisting of two
.tar.*
archives,data
andcontrol
:$ echo *.tar.* control.tar.gz data.tar.xz
While the gzip utilities are in
/bin
,unxz
is in/usr/bin
:unxz data.tar.xz
Now we have a data.tar
file without tar
to extract tar
from it.
Python to the rescue! This is where sudo
is really needed:
$ sudo python -c 'import tarfile; tarfile.open("data.tar").extractall("/")'
$ echo /bin/*
/bin/tar
Now we can use dpkg
to extract the remaining deb files to get a reasonably complete /bin
:
for i in *.deb; do dpkg-deb -x "$i" /; done
However, we should still do a proper installation of the deb files, so that symlinks etc. that would be created by packages are re-created:
sudo apt install --reinstall ./*.deb
Or:
sudo dpkg -i *.deb
sudo apt-get install -f
Notes:
We can't use Python 2 to directly extract the
data.tar.xz
file, since Python 2 only supports gzip and bzip2 compression. Python 3, however, does support it, so you can use Python 3 directly withoutunxz
:sudo python3 -c 'import tarfile; tarfile.open("data.tar.xz").extractall("/")'
- After getting back
/bin/tar
, you still need to extract some of the deb files before you can useapt-get
: the shells, coreutils, etc. Easier to just extract all of them and re-install later.
You could temporarily put files from a live CD or another system into your /bin
to make your system usable, then replace them with files from your Ubuntu installation by running apt-get install --reinstall
for packages which have stuff in /bin
.