I upgraded an old ISPConfig2 server from Debian Lenny to Debian Squeeze. Everything went fine, except one issue: openssh-client openssh-server can not be upgraded. This is what happens: apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be upgraded: openssh-client openssh-server 2 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 0 B/1,252 kB of archives. After this operation, 123 kB of additional disk space will be used. Do you want to continue [Y/n]? Y Preconfiguring packages ... (Reading database ... 56582 files and directories currently installed.) Preparing to replace openssh-server 1:5.1p1-5 (using .../openssh-server_1%3a5.5p1-6_amd64.deb) ... Unpacking replacement openssh-server ... dpkg: error processing /var/cache/apt/archives/openssh-server_1%3a5.5p1-6_amd64.deb (--unpack): unable to make backup link of `./usr/sbin/sshd' before installing new version: Operation not permitted configured to not write apport reports Preparing to replace openssh-client 1:5.1p1-5 (using .../openssh-client_1%3a5.5p1-6_amd64.deb) ... Unpacking replacement openssh-client ... dpkg: error processing /var/cache/apt/archives/openssh-client_1%3a5.5p1-6_amd64.deb (--unpack): unable to make backup link of `./usr/bin/ssh' before installing new version: Operation not permitted configured to not write apport reports dpkg-deb: subprocess paste killed by signal (Broken pipe) Errors were encountered while processing: /var/cache/apt/archives/openssh-server_1%3a5.5p1-6_amd64.deb /var/cache/apt/archives/openssh-client_1%3a5.5p1-6_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) What is the recommended way to solve this problem?