recently I met one troublesome problem with my lab ubuntu server. I want to reinstall my openssh server, so I run the command
sudo apt-get install openssh-client
sudo apt-get install openssh-server
However, the command failed with the feedback
Unpacking replacement openssh-server ...
dpkg: error processing /var/cache/apt/archives/openssh-server_1%3a7.6p1-4ubuntu0.3_amd64.deb (--unpack):
unable to make backup link of `./usr/sbin/sshd' before installing new version: Operation not permitted
According to one feasible solution(https://www.howtoforge.com/debian-ubuntu-unable-to-make-backup-link-of-usr-bin-sshd-before-installing-new-version-operation-not-permitted), it said that we should check the attribute of my /usr/bin/ssh
and /usr/bin/sshd
with chattr and lsattr command. But when I ran
sudo lsattr /usr/bin/ssh
sudo chattr /usr/bin/ssh
,it came no any output. And it seems that my lsattr/chattr command is wrong cause I check the size of lsattr and chattr, there are 10576 b and 10592 b in my other ubuntu server. But in this server, ther are only 10 b. And if I use less -SN lsattr/chattr
, they all show:
#!/bin/sh
/usr/bin/chattr (END)
#!/bin/sh
/usr/bin/lsattr (END)
And if I want to replace (with root) those chattr and lsattr with the one I copy from other server, it shows Operation not permitted
So anyone could help me with this openssh problem or reintall chattr/lsattr
?
2
Answers
I recently experienced the same problem as you. All your previous actions are correct. But Before replacing
lsattr
andchattr
, you need to modify the attributes of/usr/bin/lsattr
and/usr/bin/chattr
using the copiedchattr
.Then the replacement operation can be performed and you can modify the attributes of
/usr/sbin/sshd
.Then you can try to install
openssh
.To be on the safe side, finally add the
ai
attribute to both the replacedlsattr
andchattr
.I came across this problem, too.
Normally, the
/usr/bin/lsattr
file should be a binary executable, but I found it to be empty (with only one line#!/bin/sh
).This case, maybe we should not fix the problem by copying the correct
/usr/bin/lsattr
binary from another computer, but we should be aware that our computers are attacked!The file
/usr/bin/lsattr
is replaced, and the./usr/sbin/sshd
executable is modified, which means that the ssh is not secure any more! Attackers can log in to your computer, and take over the control. Any private information is not secure any more……