# Build trouble on Ubuntu 17.10
**URL:** https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076
**Category:** Internals & Design
**Tags:** build
**Created:** [February 15, 2018, 4:23am UTC](https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076 "2018-02-15T04:23:02Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@preda](https://discourse.julialang.org/u/preda)
#### Post date: [February 15, 2018, 4:23am UTC](https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076/1 "2018-02-15T04:23:02Z")
From fresh checked-out master source, “make” produces:
test\_potrs.o: In function `__ctest_potrf_bug_695_run': test_potrs.c:(.text+0xc4): undefined reference to `zpotrs\_’
collect2: error: ld returned 1 exit status
Makefile:21: recipe for target ‘openblas\_utest’ failed
make[3]: \*\*\* [openblas\_utest] Error 1
Makefile:116: recipe for target ‘tests’ failed
make[2]: \*\*\* [tests] Error 2
\*\*\* Clean the OpenBLAS build with ‘make -C deps clean-openblas’. Rebuild with ‘make OPENBLAS\_USE\_THREAD=0’ if OpenBLAS had trouble linking libpthread.so, and with ‘make OPENBLAS\_TARGET\_ARCH=NEHALEM’ if there were errors building SandyBridge support. Both these options can also be used simultaneously. \*\*\*
/home/preda/julia/deps/blas.mk:88: recipe for target ‘scratch/openblas-5dde4e65d321076582a2fafe16949d2160551e81/build-compiled’ failed
make[1]: \*\*\* [scratch/openblas-5dde4e65d321076582a2fafe16949d2160551e81/build-compiled] Error 1
Makefile:83: recipe for target ‘julia-deps’ failed
make: \*\*\* [julia-deps] Error 2
---
### Author:  [@jkbest2](https://discourse.julialang.org/u/jkbest2)
#### Post date: [February 15, 2018, 5:30am UTC](https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076/2 "2018-02-15T05:30:58Z")
I just ran into this. Check the [Required Build Tools and External Libraries](https://github.com/julialang/julia#required-build-tools-and-external-libraries) to make sure they’re all installed (via `apt-get` or equivalent). There were still a couple missing after I installed `build-essential`, including `gfortran`.
Otherwise, try doing what the error says, though it didn’t seem to help me:
```nohighlight
*** Clean the OpenBLAS build with ‘make -C deps clean-openblas’. Rebuild with ‘make
OPENBLAS_USE_THREAD=0’ if OpenBLAS had trouble linking libpthread.so, and with
‘make OPENBLAS_TARGET_ARCH=NEHALEM’ if there were errors building SandyBridge
support. Both these options can also be used simultaneously. ***
```
---
### Author:  [@Elrod](https://discourse.julialang.org/u/Elrod)
#### Post date: [February 15, 2018, 10:41am UTC](https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076/3 "2018-02-15T10:41:00Z")
I had OpenBLAS-related build trouble a few days ago. While the errors were different, I did finally resolve it via simply installing OpenBLAS separately and then using system BLAS.
Just create a `Make.user` with lines like:
```julia
USE_SYSTEM_BLAS=1
USE_SYSTEM_LAPACK=1
LIBBLAS=-lopenblas
LIBBLASNAME=libopenblas
LIBLAPACK=-lopenblas
LIBLAPACKNAME=libopenblas
```
The easiest way to get openblas of course is just `sudo apt-get install libopenblas-dev`.
But I’ve also found that checking out OpenBLAS and building from source: [https://github.com/xianyi/OpenBLAS](https://github.com/xianyi/OpenBLAS)
is a lot less prone to throwing errors and easier to debug than letting Julia build it.
If you’d like “inspiration” on what flags to use, you can look at:
[https://github.com/JuliaLang/julia/blob/master/deps/blas.mk](https://github.com/JuliaLang/julia/blob/master/deps/blas.mk)
---
### Author:  [@preda](https://discourse.julialang.org/u/preda)
#### Post date: [February 15, 2018, 1:15pm UTC](https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076/4 "2018-02-15T13:15:48Z")
So, were you able to fix this problem?
---
### Author:  [@preda](https://discourse.julialang.org/u/preda)
#### Post date: [February 15, 2018, 1:15pm UTC](https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076/5 "2018-02-15T13:15:51Z")
OK, just doing a clean of OpenBLAS as instructed fixes it:
make -C deps clean-openblas
---
### Author:  [@jkbest2](https://discourse.julialang.org/u/jkbest2)
#### Post date: [February 15, 2018, 3:19pm UTC](https://discourse.julialang.org/t/build-trouble-on-ubuntu-17-10/9076/6 "2018-02-15T15:19:54Z")
Yes. In my case I was on a new Ubuntu install and was missing a couple of the required programs. It compiled fine once I installed them. I think I ran ‘make clean‘ to be safe.