102.3 Manage Shared Libraries (Overview)

Question 1

Shared Libraries

reusable functions that other apps use by ‘linking’ to them within the library file

Answer 1

shared libraries

Question 2

Shared Libraries

shared libraries have the file extension

Answer 2

.so
shared object

Question 3

Shared Libraries

/lib
/usr/lib*
/usr/local/lib/*
/usr/share/*

Answer 3

common locations for shared libraries

Question 4

Shared Libraries

specific library versions linked to more generic name

Answer 4

soft links

ie: libstdc++.so > libstdc++.so>6.).19

Question 5

Shared libraries : Linking

app contains full copy of library used

Answer 5

static linking

Question 6

Shared libraries : Linking

Advantage of static linking

Answer 6

version control
app has exact library version it expects with known interfaces

Question 7

Shared libraries : Linking

Disadvantage of static linking

Answer 7

size
increases the size of the app since it includes full copy of any statically linked library

Question 8

Shared libraries : Linking

Disadvantage of static linking

Answer 8

upgrades
app needs to be recompiled and relinked anytime the library required is updated

Question 9

Shared libraries : Linking

app uses the library externally using ‘______” library that is installed on the OS itself but not the app

Answer 9

‘stubs’

Question 10

Shared libraries : Linking

Advantage of dynamic linking

Answer 10

size
app is smaller because the libs are separate from it

Question 11

Shared libraries : Linking

Advantage of dynamic linking

Answer 11

upgrades
no recompile or relinking needed

Question 12

Shared Libraries: Linking

any time an app needs to use a shared library this service is called

Answer 12

ld.so
aka dynamic linker

Question 13

Shared Libraries: Linking

shows a list of all libs the indicated dynamic executable app requries

Answer 13

ldd [filename]

Question 14

Shared Libraries: Linking

configures dynamic linker run-time bindings (creates links / caches most recent)

Answer 14

ldconfig

Question 15

Shared Libraries: linking

ldconfig

looks as specified on command line
looks as specified in the
commonly run after system updates or after 3rd party app installs

Answer 15

ls.so.conf file

Question 16

Shared Libraries: linking

ldconfig

generates ‘______” file that is a binary listing libs on system as detected

Answer 16

/etc/ld.so.cache

Question 17

Shared Libraries: linking

standard list of lib file locations listed here

Answer 17

/etc/ld.so.conf

Question 18

Shared Libraries: linking

if a line exists in the /include ld.so.conf.d/*.conf it will read all files looking for

Answer 18

libraries

Question 19

Shared Libraries: linking

any env var can be user-specific or system wide that specifies a path

Answer 19

LD_LIBRARY_PATH

Question 20

Shared Libraries: linking

typical format of LD_LIBRARY_PATH so that ld.so and ldconfig app(s) can look for libs

Answer 20

colon(:) delimited