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fundamentals/packages.md

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+# Looking
+
+Your package has something to do with unzipping.  Find out more:
+
+> apropos unzip
+
+# Maintenance
+
+> dpkg -l
+
+List what's installed.
+
+# Libraries
+
+Libraries under /lib/ typically contain an .so suffix when they're dynamic.  It means 'shared object' as a number of programs will refer to it.
+
+Others will have an /a/ suffix, meaning that they're static, and will be loaded at runtime.
+
+We can check the dependencies of a program using the ldd command upon anything in a library. For example:
+
+> ldd/usr/bin/md5sum
+
+... shows us that md5sum depends upon:
+
+- linux-vdso.so.1
+
+- libc.so.6
+
+- lib64/ld-linux-x86-64.so.2
+
+To list all libraries, run:
+
+> ldconfig -p
+
+For example, if looking at /usr/lib/x86_64-linux-gnu/libXcomposite.so.1, we might wonder what it's for.  We can then run:
+
+> ldconfig -p | grep libXcomposite
+
+... and find out nothing except that it redirects /usr/lib/x86...
+
+So at least we know where it is.
+
+> ldconfig -p | grep usb
+
+... this will show where things which nominally relate to usbs live.
+
+You can add to the libarary path by putting just any text file in /etc/ld.so.cache, e.g. in Arch where the path to the fakeroot environment is placed there.
+