Despite Settings=>Security=>Allowed File Settings:
aac,aif,aiff,asf,asx,avi,bmp,c,cc,class,css,divx,doc,docx,exe,gif,gz,gzip,h,ico,j2k,jp2,jpe,jpeg,jpg,m4a,mdb,mid,midi,mov,mp2,mp3,mp4,mpa,mpe,mpeg,mpg,mpp,odb,odc,odf,odg,odp,ods,odt,ogg, pdf,png,pot,pps,ppt,pptx,qt,ra,ram,rtf,rtx,swf,tar,tif,tiff,txt, wav,wax,wma,wmv,wmx,wri,xla,xls,xlsx,xlt,xlw,zip
I get this error when attempting to upload a tar:
[Tue Mar 15 09:56:25 2016] [error] [client 146.96.33.237] PHP Notice: Undefined index: tags in /var/www/html/legacy/application/libraries/Omeka/Controller/Pdmin/items/edit/13935