While you upgrade a plugin in WordPress, this message may bother you. It comes up when the $wp_filesystem, which is an instance of WP_Filesystem_XXX, can't create a temporary directory.
There are four WP_Filesystem classes: Direct, SSH2, FTPext, ftpsockets. And I think many of you are using WP_Filesystem_FTPext to take advantage of FTP.
In my case, VSFTPD is the problem. Because Ubuntu turns off ftp's writable feature by default, WP_Filesystem_FTPext can't make any file or directory. What I did to solve this is really simple:
- Open
/etc/vsftpd.conf - Uncomment
write_enable=YES - Restart
vsftpdservice
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