linux系统的字体目录是在/usr/share/fonts下面
下面是添加OPPOSans字体到linux系统下的指令：

hxzw@SFCS:~$ su
Password: 
root@SFCS:/home/hxzw# ls
Desktop    Public        UpgradeDaemon                   genMd5.sh
Documents  SFCS          Videos                          hxzw.sh
Downloads  SFCS-CQ       build-SFCS-CQ-Desktop-Debug     modbus
Music      SFCS-NEWUI    build-SFCS-CQ-Desktop-Release   serialport
OPPOSans   Templates     build-SFCS-Desktop-Debug        websocket
Pictures   UpgradeCheck  build-SFCS-NEWUI-Desktop-Debug  xrecord
root@SFCS:/home/hxzw# cp OPPOSans/ /usr/share/font
fontconfig/           fonts-droid-fallback/ 
fonts/                fonts-hack/           
root@SFCS:/home/hxzw# cp OPPOSans/ /usr/share/fonts/truetype/
cp: -r not specified; omitting directory 'OPPOSans/'
root@SFCS:/home/hxzw# cp -p -r OPPOSans/ /usr/share/fonts/truetype/OPPOSans
root@SFCS:/home/hxzw# cd /usr/share/fonts/truetype/
root@SFCS:/usr/share/fonts/truetype# ls
OPPOSans  dejavu  droid  freefont  hack  noto  quicksand  ubuntu
root@SFCS:/usr/share/fonts/truetype# ls -ld ubuntu/
drwxr-xr-x 2 root root 4096 Apr 24  2023 ubuntu/
root@SFCS:/usr/share/fonts/truetype# ls -l OPPOSans
total 33888
-rw------- 1 hxzw hxzw  9897168 Jul 26 17:20 OPPOSans-B.ttf
-rw------- 1 hxzw hxzw  2219752 Jul 26 17:20 OPPOSans-H.ttf
-rw------- 1 hxzw hxzw  2340400 Jul 26 17:20 OPPOSans-L.ttf
-rw------- 1 hxzw hxzw 10080628 Jul 26 17:20 OPPOSans-M.ttf
-rw------- 1 hxzw hxzw 10152780 Jul 26 17:20 OPPOSans-R.ttf
root@SFCS:/usr/share/fonts/truetype# ls -ld OPPOSans
drwx------ 2 hxzw hxzw 4096 Jul 26 17:20 OPPOSans
root@SFCS:/usr/share/fonts/truetype# chmod 755 OPPOSans/
root@SFCS:/usr/share/fonts/truetype# ls -l ubuntu/
total 4308
-rw-r--r-- 1 root root 333612 Jul 10  2015 Ubuntu-B.ttf
-rw-r--r-- 1 root root 356980 Jul 10  2015 Ubuntu-BI.ttf
-rw-r--r-- 1 root root 350444 Jul 10  2015 Ubuntu-C.ttf
-rw-r--r-- 1 root root 415552 Jul 10  2015 Ubuntu-L.ttf
-rw-r--r-- 1 root root 409608 Jul 10  2015 Ubuntu-LI.ttf
-rw-r--r-- 1 root root 341324 Jul 10  2015 Ubuntu-M.ttf
-rw-r--r-- 1 root root 366992 Jul 10  2015 Ubuntu-MI.ttf
-rw-r--r-- 1 root root 353824 Jul 10  2015 Ubuntu-R.ttf
-rw-r--r-- 1 root root 386440 Jul 10  2015 Ubuntu-RI.ttf
-rw-r--r-- 1 root root 240020 Mar  8  2019 Ubuntu-Th.ttf
-rw-r--r-- 1 root root 191400 Sep 26  2011 UbuntuMono-B.ttf
-rw-r--r-- 1 root root 216208 Sep 26  2011 UbuntuMono-BI.ttf
-rw-r--r-- 1 root root 205748 Sep 26  2011 UbuntuMono-R.ttf
-rw-r--r-- 1 root root 210216 Sep 26  2011 UbuntuMono-RI.ttf
root@SFCS:/usr/share/fonts/truetype# chmod 644 OPPOSans/*.ttf
root@SFCS:/usr/share/fonts/truetype# ls -l OPPOSans/
total 33888
-rw-r--r-- 1 hxzw hxzw  9897168 Jul 26 17:20 OPPOSans-B.ttf
-rw-r--r-- 1 hxzw hxzw  2219752 Jul 26 17:20 OPPOSans-H.ttf
-rw-r--r-- 1 hxzw hxzw  2340400 Jul 26 17:20 OPPOSans-L.ttf
-rw-r--r-- 1 hxzw hxzw 10080628 Jul 26 17:20 OPPOSans-M.ttf
-rw-r--r-- 1 hxzw hxzw 10152780 Jul 26 17:20 OPPOSans-R.ttf
root@SFCS:/usr/share/fonts/truetype# exit
exit
hxzw@SFCS:~$ sudo fc-cache -f -v
[sudo] password for hxzw: 
/usr/share/fonts: caching, new cache contents: 0 fonts, 6 dirs
/usr/share/fonts/X11: caching, new cache contents: 0 fonts, 3 dirs
/usr/share/fonts/X11/encodings: caching, new cache contents: 0 fonts, 1 dirs
/usr/share/fonts/X11/encodings/large: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/X11/misc: caching, new cache contents: 89 fonts, 0 dirs
/usr/share/fonts/X11/util: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/cMap: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/cmap: caching, new cache contents: 0 fonts, 5 dirs
/usr/share/fonts/cmap/adobe-cns1: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/cmap/adobe-gb1: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/cmap/adobe-japan1: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/cmap/adobe-japan2: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/cmap/adobe-korea1: caching, new cache contents: 0 fonts, 0 dirs
/usr/share/fonts/opentype: caching, new cache contents: 0 fonts, 1 dirs
/usr/share/fonts/opentype/urw-base35: caching, new cache contents: 35 fonts, 0 dirs
/usr/share/fonts/truetype: caching, new cache contents: 0 fonts, 8 dirs
/usr/share/fonts/truetype/OPPOSans: caching, new cache contents: 5 fonts, 0 dirs
/usr/share/fonts/truetype/dejavu: caching, new cache contents: 6 fonts, 0 dirs
/usr/share/fonts/truetype/droid: caching, new cache contents: 1 fonts, 0 dirs
/usr/share/fonts/truetype/freefont: caching, new cache contents: 12 fonts, 0 dirs
/usr/share/fonts/truetype/hack: caching, new cache contents: 4 fonts, 0 dirs
/usr/share/fonts/truetype/noto: caching, new cache contents: 1 fonts, 0 dirs
/usr/share/fonts/truetype/quicksand: caching, new cache contents: 4 fonts, 0 dirs
/usr/share/fonts/truetype/ubuntu: caching, new cache contents: 14 fonts, 0 dirs
/usr/share/fonts/type1: caching, new cache contents: 0 fonts, 1 dirs
/usr/share/fonts/type1/urw-base35: caching, new cache contents: 35 fonts, 0 dirs
/usr/local/share/fonts: caching, new cache contents: 0 fonts, 0 dirs
/root/.local/share/fonts: skipping, no such directory
/root/.fonts: skipping, no such directory
/usr/share/fonts/X11: skipping, looped directory detected
/usr/share/fonts/cMap: skipping, looped directory detected
/usr/share/fonts/cmap: skipping, looped directory detected
/usr/share/fonts/opentype: skipping, looped directory detected
/usr/share/fonts/truetype: skipping, looped directory detected
/usr/share/fonts/type1: skipping, looped directory detected
/usr/share/fonts/X11/encodings: skipping, looped directory detected
/usr/share/fonts/X11/misc: skipping, looped directory detected
/usr/share/fonts/X11/util: skipping, looped directory detected
/usr/share/fonts/cmap/adobe-cns1: skipping, looped directory detected
/usr/share/fonts/cmap/adobe-gb1: skipping, looped directory detected
/usr/share/fonts/cmap/adobe-japan1: skipping, looped directory detected
/usr/share/fonts/cmap/adobe-japan2: skipping, looped directory detected
/usr/share/fonts/cmap/adobe-korea1: skipping, looped directory detected
/usr/share/fonts/opentype/urw-base35: skipping, looped directory detected
/usr/share/fonts/truetype/OPPOSans: skipping, looped directory detected
/usr/share/fonts/truetype/dejavu: skipping, looped directory detected
/usr/share/fonts/truetype/droid: skipping, looped directory detected
/usr/share/fonts/truetype/freefont: skipping, looped directory detected
/usr/share/fonts/truetype/hack: skipping, looped directory detected
/usr/share/fonts/truetype/noto: skipping, looped directory detected
/usr/share/fonts/truetype/quicksand: skipping, looped directory detected
/usr/share/fonts/truetype/ubuntu: skipping, looped directory detected
/usr/share/fonts/type1/urw-base35: skipping, looped directory detected
/usr/share/fonts/X11/encodings/large: skipping, looped directory detected
/var/cache/fontconfig: cleaning cache directory
/root/.cache/fontconfig: not cleaning non-existent cache directory
/root/.fontconfig: not cleaning non-existent cache directory
fc-cache: succeeded
hxzw@SFCS:~$