how to make "xhost +local:host" be effective forever so I do not need to set it everytime the computer boots？

Question

I tried to wirte this command xhost +local:host into a shell and write a crontab to excute this shell. But I failed.

Here's my shell:

#!/bin/bash
source /etc/profile
export DISPLAY=:0.0
/usr/bin/xhost +local:root

Here's my crontab:

@reboot /bin/bash /home/pi/shell2.sh 2>&1 >/dev/null | tee a /home/pi/shell2.log

After rebooting,I checked the log and it says:

/usr/bin/xhost: unable to open dispaly ":0.0"

I feel really confused. I can excute this shell manually but I can't make it excute automatilly when boots.And when I excute xhost +local:host on the terminal it works fine.

I typed env in terminal and this is the result

XDG_VTNR=7
INFINALITY_FT_AUTOHINT_HORIZONTAL_STEM_DARKEN_STRENGTH=10
SSH_AGENT_PID=1383
XDG_SESSION_ID=c1
SAL_USE_VCLPLUGIN=gtk
CLUTTER_IM_MODULE=xim
XDG_GREETER_DATA_DIR=/var/lib/lightdm/data/pi
TERM=xterm
INFINALITY_FT_AUTOHINT_VERTICAL_STEM_DARKEN_STRENGTH=25
SHELL=/bin/bash
XDG_MENU_PREFIX=lxde-pi-
INFINALITY_FT_BOLD_EMBOLDEN_X_VALUE=0
INFINALITY_FT_CONTRAST=0
USER=pi
INFINALITY_FT_GRAYSCALE_FILTER_STRENGTH=0
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.axa=00;36:*.oga=00;36:*.spx=00;36:*.xspf=00;36:
XDG_SESSION_PATH=/org/freedesktop/DisplayManager/Session0
XDG_SEAT_PATH=/org/freedesktop/DisplayManager/Seat0
SSH_AUTH_SOCK=/tmp/ssh-r0hSj9VyFxKm/agent.1144
INFINALITY_FT_FRINGE_FILTER_STRENGTH=0
INFINALITY_FT_BRIGHTNESS=0
INFINALITY_FT_USE_VARIOUS_TWEAKS=true
INFINALITY_FT_GAMMA_CORRECTION=0 100
XDG_CONFIG_DIRS=/etc/xdg
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games
DESKTOP_SESSION=LXDE-pi
QT_IM_MODULE=fcitx
PWD=/home/pi
XMODIFIERS=@im=fcitx
LANG=en_GB.UTF-8
INFINALITY_FT_FILTER_PARAMS=11 22 38 22 11
INFINALITY_FT_USE_KNOWN_SETTINGS_ON_SELECTED_FONTS=true
INFINALITY_FT_STEM_SNAPPING_SLIDING_SCALE=40
INFINALITY_FT_WINDOWS_STYLE_SHARPENING_STRENGTH=10
INFINALITY_FT_CHROMEOS_STYLE_SHARPENING_STRENGTH=0
INFINALITY_FT_STEM_ALIGNMENT_STRENGTH=25
INFINALITY_FT_AUTOHINT_SNAP_STEM_HEIGHT=100
GDMSESSION=lightdm-xsession
_LXSESSION_PID=1144
SHLVL=1
XDG_SEAT=seat0
HOME=/home/pi
XDG_CONFIG_HOME=/home/pi/.config
INFINALITY_FT_BOLD_EMBOLDEN_Y_VALUE=0
INFINALITY_FT_GLOBAL_EMBOLDEN_Y_VALUE=0
LOGNAME=pi
QT4_IM_MODULE=fcitx
XDG_DATA_DIRS=/usr/local/share:/usr/share/raspi-ui-overrides:/usr/share:/usr/share/gdm:/var/lib/menu-xdg
DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-fBM7nLHTLN,guid=863c2d8c9c28f93d365b95f0597af05d
INFINALITY_FT_STEM_FITTING_STRENGTH=25
INFINALITY_FT_AUTOHINT_INCREASE_GLYPH_HEIGHTS=true
TEXTDOMAIN=im-config
XDG_RUNTIME_DIR=/run/user/1000
INFINALITY_FT_GLOBAL_EMBOLDEN_X_VALUE=0
DISPLAY=:0.0
XDG_CURRENT_DESKTOP=LXDE
GTK_IM_MODULE=fcitx
TEXTDOMAINDIR=/usr/share/locale/
XAUTHORITY=/home/pi/.Xauthority
_=/usr/bin/env

Why can't it excute automatically??? Can anyone tell me how to solve this? Many many thanks!

Sincerely,Helen

Answer 1

because cron script is not launched from an X session, you need to set the DISPLAY environment variable to your script: xhost +local:host becomes DISPLAY=:0 xhost +local:host. As what I know, crontab does not inherit your env, all the PATH must be set or explicitly specified for it to find location of xhost, and of course the $DISPLAY variable must be set also. Update: update XAUTHORITY=/home/pi/.Xauthority may also help