Você corrompeu o download.
Remover o arquivo problemático e tentar novamente:
sudo rm /var/cache/apt/archives/libc6-dbg_2.26-6_i386.deb
sudo apt-get install -f
(Reading database ... 166 files and directories currently installed.)
Preparing to unpack .../libc6-dbg_2.26-6_i386.deb ...
Unpacking libc6-dbg:i386 (2.26-6) over (2.25-5) ...
dpkg-deb (subprocess): decompressing archive member: lzma error: compressed data is corrupt
dpkg-deb: error: <decompress> subprocess returned error exit status 2
dpkg: error processing archive /var/cache/apt/archives/libc6-dbg_2.26-6_i386.deb (--unpack):
cannot copy extracted data for './usr/lib/debug/.build-id/b7/d4c76439e3e67b30d081161328b4388778aee6.debug' to '/usr/lib/debug/.build-id/b7/d4c76439e3e67b30d081161328b4388778aee6.debug.dpkg-new': unexpected end of file or stream
Errors were encountered while processing:
/var/cache/apt/archives/libc6-dbg_2.26-6_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
O que devo fazer?
Você corrompeu o download.
Remover o arquivo problemático e tentar novamente:
sudo rm /var/cache/apt/archives/libc6-dbg_2.26-6_i386.deb
sudo apt-get install -f