root@db2:~# apt-get -y upgrade bash
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  linux-image-server linux-server ntfs-3g openssh-client openssh-server postfix postfix-mysql
The following packages will be upgraded:
  apache2 apache2-mpm-prefork apache2-utils apache2.2-common bind9 bind9-doc bind9-host bzip2 cpio curl dnsutils libbind9-30 libbz2-1.0 libcupsys2 libcurl3 libcurl3-gnutls libdbus-1-3 libdns32 libgnutls13 libisc32 libisccc30
  libisccfg30 libkrb53 liblwres30 libpcre3 libpq5 libssl0.9.8 libuuid1 libvolume-id0 libxml2 linux-libc-dev logrotate mysql-server-5.0 ntpdate openssl python2.5 python2.5-minimal rsync samba samba-common samba-doc smbclient smbfs
  tzdata udev vim-common vim-tiny volumeid winbind
49 upgraded, 0 newly installed, 0 to remove and 7 not upgraded.
1 not fully installed or removed.
Need to get 342kB/64.7MB of archives.
After unpacking 434kB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
  libpq5
E: There are problems and -y was used without --force-yes
root@db2:~# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  linux-image-server linux-server ntfs-3g openssh-client openssh-server postfix postfix-mysql
The following packages will be upgraded:
  apache2 apache2-mpm-prefork apache2-utils apache2.2-common bind9 bind9-doc bind9-host bzip2 cpio curl dnsutils libbind9-30 libbz2-1.0 libcupsys2 libcurl3 libcurl3-gnutls libdbus-1-3 libdns32 libgnutls13 libisc32 libisccc30
  libisccfg30 libkrb53 liblwres30 libpcre3 libpq5 libssl0.9.8 libuuid1 libvolume-id0 libxml2 linux-libc-dev logrotate mysql-server-5.0 ntpdate openssl python2.5 python2.5-minimal rsync samba samba-common samba-doc smbclient smbfs
  tzdata udev vim-common vim-tiny volumeid winbind
49 upgraded, 0 newly installed, 0 to remove and 7 not upgraded.
1 not fully installed or removed.
Need to get 342kB/64.7MB of archives.
After unpacking 434kB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
  libpq5
Install these packages without verification [y/N]? y
Err http://fr.archive.ubuntu.com gutsy-backports/main libpq5 8.3.3-1~gutsy1
  404 Not Found [IP: 91.189.91.15 80]
Failed to fetch http://fr.archive.ubuntu.com/ubuntu/pool/main/p/postgresql-8.3/libpq5_8.3.3-1~gutsy1_i386.deb  404 Not Found [IP: 91.189.91.15 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
root@db2:~#