When I use drush to download modules, I get this weird error:

drush dl registry_rebuild exec(): Unable to fork [wget --version 2>&1] exec.inc:150 [warning] exec(): Unable to fork [curl --version 2>&1] exec.inc:150 [warning] exec(): Unable to fork [which curl 2>&1] exec.inc:150 [warning] wget nor curl executables found. [error]

which wget gives me /usr/bin/wget and which curl gives me /usr/bin/curl. /usr/bin/ is in my PATH. This seldom works if I do drush cc drush. How do I solve this permanently?

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    That error in on windows. Besides, my error goes away temporarily if I do a drush cc drush – Kartagis Mar 4 '14 at 7:03
  • which OS you are using? – user12947 Mar 4 '14 at 7:43
  • I am using CentOS. – Kartagis Mar 4 '14 at 8:39
  • I tried to download and enable facetapi, and I got the errors again. I cc'd all, then there were no problems. – Kartagis Mar 4 '14 at 21:53

On Centos, to install wget:

sudo yum install wget

To install curl the following should suffice:

sudo yum install php-curl
sudo service httpd restart

++++++++++++++++++++ EDIT +++++++++++++++++++++++++

According to this post, "unable to fork" errors are likely to result from too many processes running. They recommend increasing the limit like so:

sysctl -w kern.maxprocs=1000000
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  • The op states that the commands are installed, this is tested by using 'which'. – Letharion Mar 4 '14 at 15:11
  • well that's how you install them. :) if it says they're installed, you should be able to use them. If you can't, it's possibly because the path hasn't been exported. – Ollie Mar 4 '14 at 15:29
  • Right, I realize that's how they are installed, but that doesn't answer the question. It possibly is a path issue, but the op also states that the relevant directory is in the PATH already. – Letharion Mar 4 '14 at 17:10
  • oops, you're right. :s I've edited my answer to be more relevant. – Ollie Mar 4 '14 at 19:05
  • sysctl -w kern.maxprocs=1000000 error: "kern.maxprocs" is an unknown key – Kartagis Jun 13 '15 at 20:13

On nginx on aws, I've found the php-fpm can get out of hand. To tell if that's happened, ps -ef |grep php-fpm|wc -l. If the number is more than 10 or so, you can reset php-fpm with: sudo service php-fpm restart

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I fix the "Unable to fork could" with Drush by restarting my server. I think @Ollie's anwser is right.

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