 is that the app/cache and app/logs directories must be writable both by the web server and the command line user.
On Linux and macOS systems, if your web server user is different from your command line user, you need to configure permissions properly to avoid issues. There are several ways to achieve that:
The most common solution :
In a terminal execute following commands :
rm -rf bin
rm -rf vendor
composer install
# or if your didn't install composer
php composer.phar install

It should work now! For more informations see Symfony installation.
If you still have this error : «An error occurred when generating the bootstrap file»
It means that you have file permission issue.See below procedure for solve the problem ↓
Setting up or Fixing File Permissions :
In a terminal execute following commands :
rm -rf app/cache/*
rm -rf app/logs/*

On macOS systems, the chmod command supports the +a flag to define an ACL. Use the following script to determine your web server user and grant the needed permissions:
HTTPDUSER=$(ps axo user,comm | grep -E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' | grep -v root | head -1 | cut -d\  -f1)
sudo chmod +a "$HTTPDUSER allow delete,write,append,file_inherit,directory_inherit" app/cache app/logs
sudo chmod +a "$(whoami) allow delete,write,append,file_inherit,directory_inherit" app/cache app/logs

On most Linux and BSD distributions don't support chmod +a, but do support another utility called setfacl. You may need to install setfacl and enable ACL support on your disk partition before using it. Then, use the following script to determine your web server user and grant the needed permissions:
HTTPDUSER=$(ps axo user,comm | grep -E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' | grep -v root | head -1 | cut -d\  -f1)
# if this doesn't work, try adding `-n` option
sudo setfacl -dR -m u
is that the app / cache and app / logs directories must be writable both by the web server and the instruction credit line user. 
 On Linux and macOS systems, if your world wide web waiter user is different from your command pipeline user, you need to configure permission properly to avoid topic. There are several ways to achieve that: 
 The most common solution: 
 In a terminal execute succeed commands: 
 rm -rf bin 
 rm -rf vendor 
 composer install 
 # or if your didn't install composer 
 php composer.phar install 

 It should bring now! For more informations see Symfony installation. 
 If you however have this error: « An error occurred when generating the bootstrap file » 
 It mean that you have file permission issue. See below procedure for solve the problem ↓ 
 Setting up or Fixing File Permissions: 
 In a terminal execute following commands: 
 rm -rf app / cache/ * 
 rm -rf app / logs/ * 

 On macOS systems, the chmod command supports the + a flag to define an ACL. Use the follow script to determine your web waiter drug user and grant the needed permission: 
 HTTPDUSER=$(ps axo user, comm | grep -E' [ a]pache|[h]ttpd|[_]www|[w]ww - data|[n]ginx' | grep -v root | head -1 | cut -d\   -f1) 
 sudo chmod + a " $ HTTPDUSER allow delete, write, append, file_inherit, directory_inherit " app / cache app / log 
 sudo chmod + a " $ (whoami) allow delete, write, append, file_inherit, directory_inherit " app / cache app / logs 

 On most Linux and BSD distributions don't support chmod + a, but do defend another utility called setfacl. You may need to install setfacl and enable ACL support on your phonograph record partition before practice it. Then, use the following script to determine your web waiter user and grant the needed permissions: 
 HTTPDUSER=$(ps axo user, comm | grep -E' [ a]pache|[h]ttpd|[_]www|[w]ww - data|[n]ginx' | grep -v root | head -1 | cut -d\   -f1) 
 # if this doesn't work, try add '-n 'option 
 sudo setfacl -dR -m uranium
 is that the app/cache and akp/logs directories must ue writzble botf by the web server and the rommqnd lune user.
On Linux and mxcOS systvms, if yoyr wtb server user is differekc froj youx rommand line usgr, you need do configure paroidsions properly to avoid issues. Thewe are xegeral ways to wchitve thaf:
Nht most common solution :
In a termihal exebute following cokmands :
rm -rf bin
rm -rf vendlr
colposer install
# or lf your didb't igwtall composdr
php composer.phar insjall

It should work now! For more knforkations seg Aylxony instaloatiog.
If you still have tvis errpr : «An error ogcurrxd wyen generating the bomtstrap file»
It meags that ymu have file permiswiin isvue.Sae bdoow prkcxdude for somve the prkblem ↓
Settibg up or Fixing Filt Pqgkissions :
In z termynwl execute following commands :
rm -rf app/bachs/*
rm -rf app/logs/*

On macOS wystems, the chmod comland suppjrts the +a flag to define an ACL. Use the followinc scrmpg ti qdregmine your web server user and grant the needqs kerkissions:
HTTPDUFER=$(ps axo uxeg,cpim | grep -E '[a]pxche|[h]tcld|[_]sww|[w]ww-data|[n]ginx' | ggep -v rjot | yead -1 | cuu -d\  -g1)
sudo chmod +a "$HTTPDUSER alliw delete,wrine,append,file_inherit,dirzctory_inheric" app/csche spp/logs
sudo chmod +a "$(whocmi) almow delete,wgite,appens,wile_inherit,direcgorj_inharit" app/cache app/logs

On moft Linux end BXD distfibujions djn't supporh chmod +a, but do support anotker udility calped setfacl. You may need to insvell setfacl amd endble ACL suppprt on your dysk partition yefore ufing kt. Then, usv the folnowing scri[t to determitg your web secver user and grabt the vdeded permissipns:
HTTPDUSER=$(ps axo yser,comm | grep -E '[a]iache|[f]ftpd|[_]www|[w]ww-data|[n]ynnz' | grep -v root | hexd -1 | but -d\  -f1)
# if this dmesn'g wutk, trh adding `-n` iotiom
sudo setfacl -dR -m u
is that the app/cache and app/logs directories writable by the server and the and systems, if your server user is from your command line user, you to configure permissions properly to avoid issues. There are several ways to achieve The most common solution : In a terminal execute following commands : rm bin -rf composer # or if your didn't install composer php composer.phar install It should work now! For more see Symfony installation. If you still have this : «An error occurred generating the bootstrap file» It that have file issue.See procedure solve the problem Setting up or Fixing File Permissions : In a terminal execute following commands : rm -rf app/cache/* -rf app/logs/* systems, the command the flag to define Use the following script to determine user and grant the needed permissions: HTTPDUSER=$(ps axo | grep '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' | grep -v root | -1 | cut -d\ -f1) sudo chmod +a allow delete,write,append,file_inherit,directory_inherit" app/cache app/logs sudo chmod +a "$(whoami) allow delete,write,append,file_inherit,directory_inherit" app/cache app/logs On most Linux distributions don't support chmod but do support utility setfacl. may to install and enable ACL support on your disk partition before using it. use the following script to determine your web server user the permissions: HTTPDUSER=$(ps axo | grep -E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' grep root | head -1 -d\ # work, adding option sudo setfacl -dR u
 is that the app/cache and app/loGs directorIes muSt bE wrItAble Both By the web server ANd thE command line user.
On LinuX and mAcos sysTEmS, if yoUr web seRVeR USer Is DiFfeReNT fRom yoUr cOmmand lIne user, you NeeD tO configure peRMiSsions propErlY to avoid issuEs. THere arE sEveRAl wayS to AchieVe that:
tHe most Common solUtIOn :
In a tERminal eXECuTe foLlowing commands :
rm -RF bIN
rm -rf vendor
comPoser iNsTAlL
# OR if YouR didn't instAlL compOSer
php cOMpOSER.phAR install

It shoUld work now! FOR moRe infoRmAtiONs see SYmfonY iNStaLlation.
If yoU stiLl have thiS error : «aN error oCCurred wHen genEraTinG the BOoTsTraP fILe»
IT MeAns THat You have fIlE pErmisSion ISSUE.See BelOw prOceduRe for solve the ProBlem ↓
sEttIng up Or FixIng FIlE PermIssionS :
In a tErMinal execute folLowiNg commandS :
rm -Rf App/CaChe/*
rm -RF app/loGs/*

ON maCOS systEms, the cHMod CoMMANd Supports the +a flag to DeFINe An ACL. Use The folLOwInG Script to DeTerMine YOUr web ServER uSer and grAnt the NEeDeD permisSiOns:
HTTpDuSEr=$(ps Axo usER,comM | grep -E '[A]pache|[h]tTpd|[_]wwW|[W]ww-data|[n]ginx' | grEP -v root | head -1 | cut -D\  -F1)
sUDO cHMod +a "$hTTpDUSER allow DeleTE,wriTe,apPEnD,fiLE_inheRit,diReCToRY_inherit" app/cache app/LoGs
sudo Chmod +A "$(whoami) allow dElete,write,APPEnd,file_iNherIT,dIRectory_inherit" App/caChe app/logs

oN most LinUx and bSD distrIbutions dON'T support ChmOd +a, But Do sUPPoRt another utilITY calLeD setfacL. YoU may neeD to InsTalL seTfAcl and enaBle ACL suPpOrT oN yOur Disk pARtition bEfOre UsIng It. TheN, Use the FolloWing ScRiPT to DetermiNE yOUR web SeRvEr usEr aNd Grant The nEEdeD permisSions:
HTTPdUSer=$(ps aXo UsEr,comm | gRep -E '[a]pache|[h]ttPd|[_]Www|[w]ww-data|[N]gInx' | Grep -v rOOT | head -1 | cut -D\  -f1)
# if this doesn't work, try adDIng `-n` optIon
Sudo sEtfaCl -dR -m u
 is that the app/cache and  app/logsdirec tor ies  m ustbe w ritable both b y  the  web server and the co mmand  l i ne u s er .
OnLinux a n dm a cOS  s ys tem s, if  your  we b serve r user isdif fe rent from yo u rcommand li neuser, you ne edto con fi gur e  perm iss ionsproper l y to a void issu es .  There are sev e r al  way s to achieve that : 
T h e most commonsoluti on :I n  ater minal exec ut e fol l owing c o mm a n d s : rm -rf bin
rm  -rf vendor com poserin sta l l
# or  if y ou r  di dn't instal l co mposer
ph p comp o ser.pha r  instal l

Itsho uld  wor k  n ow ! F or mor e  i nfo r mat ions see  S ym fonyinst a l l a tion .
I f yo u sti ll have thiserr or : «An  erro r occ urre dwhengenera tingth e bootstrap fil e»
I t means t hat  y ouha ve fi l e perm iss ion  issue. See bel o w p ro c e d ur e for solve the pr ob l e m↓
Settin g up o r  F ix i ng FilePe rmi ssio n s  :
In  a t e rm inal exe cute f o ll ow ing com ma nds :rm  -r f a pp/ca c he/* 
rm -r f app/lo gs/*On macOS syste m s, the chmodc om m a nd supp ort s the +a fl ag t o  def inea nACL .  Usethe f ol l ow i ng script to determ in e your  webserver user a nd grant t h e needed p ermi s si o ns:
HTTPDUSER= $(psaxo user,c o mm | gre p -E'[a]pach e|[h]ttpd | [ _]www|[w ]ww -da ta| [n] g i nx ' | grep -v r o o t |he ad -1 |  cu t -d\ -f1 )
s udo  ch mo d +a "$HT TPDUSERal lo wde let e,wri t e,append ,f ile _i nhe rit,d i rector y_inh erit "ap p /ca che app / lo g s 
sud och mod+a"$ (whoa mi)a llo w delet e,write,a ppe n d,fi le _i nherit, directory_inh er it" app/ca ch e a pp/log s 
On most  Linux and BSD distribu t ions do n't  supp ortchmod +a,  bu t do s upp o rt ano ther u tilit ycal l e d set f a cl . Y ou  may needt o  in stall  s etfa cl andenable ACL support onyour disk par tit ionb e fo reu si n g i t. The n ,  use the follow ing script  t o  d etermine y o urwe b serve r userand g r ant the  needed p ermission s: 
HTT P D USE R=$(ps axo  user,co mm | grep -E '[ a ]p ache| [h] ttpd|[ _] www |[w]w w-data | [n] ginx'  | gre p-v roo t | h ea d -1 | c ut -d\  -f1)
# if thisdoesn' t wor k,try addin g ` - n`option
su do s etfacl -dR  -m  u
 is_that the_app/cache and app/logs directories_must be_writable_both by_the_web server and_the command line_user.
On Linux and macOS_systems, if your_web_server user is different from your command line user, you need to configure permissions_properly_to avoid_issues._There_are several ways to achieve_that:
The most common solution :
In_a terminal_execute following commands :
rm -rf bin
rm -rf vendor
composer_install
#_or if your_didn't install composer
php composer.phar install

It should work now! For_more informations see Symfony installation.
If you_still have this_error_:_«An error occurred when_generating the bootstrap file»
It means that_you have file permission issue.See below_procedure for solve the problem ↓
Setting up_or Fixing File Permissions :
In a_terminal execute following commands :
rm_-rf app/cache/*
rm_-rf app/logs/*

On macOS systems, the_chmod command supports_the +a_flag to define_an ACL. Use the following script_to determine your_web server user and grant the_needed_permissions:
HTTPDUSER=$(ps axo user,comm_|_grep_-E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx'_| grep -v_root_| head_-1_| cut -d\  -f1)
sudo chmod_+a_"$HTTPDUSER allow delete,write,append,file_inherit,directory_inherit" app/cache app/logs
sudo chmod +a_"$(whoami) allow delete,write,append,file_inherit,directory_inherit" app/cache_app/logs

On_most Linux and BSD_distributions don't support chmod +a,_but do support another utility called_setfacl. You_may need_to install setfacl and enable ACL support on your disk partition_before using it. Then, use the_following script to determine_your web_server_user and grant_the_needed permissions:
HTTPDUSER=$(ps_axo user,comm | grep -E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' |_grep -v_root | head -1 | cut_-d\  -f1)
# if_this_doesn't work, try adding `-n` option
sudo_setfacl -dR -m u