~ $ stack setup --help
...
  --[no-]reinstall         Enable/disable reinstalling GHC, even if available
                           (implies no-system-ghc)
...
~ $ stack setup
Run from outside a project, using implicit global project config
Using resolver: nightly-2016-08-25 from implicit global project's config file: /home/simon/.stack/global-project/stack.yaml
stack will use a sandboxed GHC it installed
For more information on paths, see 'stack path' and 'stack exec env'
To use this GHC and packages outside of a project, consider using:
stack ghc, stack ghci, stack runghc, or stack exec
~ $ stack setup --reinstall -v
Version 1.2.1, Git revision a77c00b92b6edfb1ffd99a3fea9fd54b9ab1c66c (dirty) (4047 commits) x86_64 hpack-0.14.1
2016-09-01 04:07:53.920464: [debug] Checking for project config at: /home/simon/stack.yaml
@(Stack/Config.hs:797:9)
2016-09-01 04:07:53.920826: [debug] Checking for project config at: /home/stack.yaml
@(Stack/Config.hs:797:9)
2016-09-01 04:07:53.921018: [debug] Checking for project config at: /stack.yaml
@(Stack/Config.hs:797:9)
2016-09-01 04:07:53.921154: [debug] No project config file found, using defaults.
@(Stack/Config.hs:819:13)
2016-09-01 04:07:53.923710: [info] Run from outside a project, using implicit global project config
@(Stack/Config.hs:432:13)
2016-09-01 04:07:53.924760: [info] Using resolver: nightly-2016-08-25 from implicit global project's config file: /home/simon/.stack/global-project/stack.yaml
@(Stack/Config.hs:446:32)
2016-09-01 04:07:53.925006: [debug] Trying to decode /home/simon/.stack/build-plan-cache/x86_64-linux/nightly-2016-08-25.cache
@(Data/Store/VersionTagged.hs:68:5)
2016-09-01 04:07:53.946823: [debug] Success decoding /home/simon/.stack/build-plan-cache/x86_64-linux/nightly-2016-08-25.cache
@(Data/Store/VersionTagged.hs:72:13)
2016-09-01 04:07:53.954226: [debug] Run process: /sbin/ldconfig -p
@(System/Process/Read.hs:277:3)
2016-09-01 04:07:53.957091: [debug] Process finished in 2 ms: /sbin/ldconfig -p
@(System/Process/Read.hs:277:3)
2016-09-01 04:07:53.958039: [debug] Did not find libtinfo.so.6 or libgmp.so.3; using standard GHC build
@(Stack/Setup.hs:503:25)
2016-09-01 04:07:53.960657: [debug] Performing a sanity check on: /home/simon/.stack/programs/x86_64-linux/ghc-8.0.1/bin/ghc
@(Stack/Setup.hs:1450:5)
2016-09-01 04:07:53.961316: [debug] Run process: /home/simon/.stack/programs/x86_64-linux/ghc-8.0.1/bin/ghc /tmp/stack-sanity-check17467/Main.hs -no-user-package-db
@(System/Process/Read.hs:277:3)
2016-09-01 04:07:54.620799: [debug] Process finished in 659 ms: /home/simon/.stack/programs/x86_64-linux/ghc-8.0.1/bin/ghc /tmp/stack-sanity-check17467/Main.hs -no-user-package-db
@(System/Process/Read.hs:277:3)
2016-09-01 04:07:54.621690: [info] stack will use a sandboxed GHC it installed
@(Stack/SetupCmd.hs:105:19)
2016-09-01 04:07:54.621794: [info] For more information on paths, see 'stack path' and 'stack exec env'
@(Stack/SetupCmd.hs:106:5)
2016-09-01 04:07:54.621900: [info] To use this GHC and packages outside of a project, consider using:
@(Stack/SetupCmd.hs:107:5)
2016-09-01 04:07:54.621991: [info] stack ghc, stack ghci, stack runghc, or stack exec
@(Stack/SetupCmd.hs:108:5)