diff -qr /path1/dir1/ /path2/dir2/

apt list –installed | grep packagename

dpkg-query -l

Find installed rpms
rpm -qa | grep packagename

Find the latest installed rpms
rpm -qa –last

If you know the month the backup was ran (eg. January) type the following:
rpm -qa –last | grep Jan

Newer version of dmesg
dmesg -T

Older versions of dmesg
dmesg|perl -ne ‘BEGIN{$a= time()- qx!cat /proc/uptime!};s/( *)(\d+).\d+/localtime($2 + $a)/e; print $_;’

sysctl -a