The most common permissions include:
400 r——– files (won’t let you accidentally erase)
444 r–r–r– files (lets everyone read)
600 rw——- files (no one else can read or see files)
644 rw-r–r– files (owner can read/write, group read, public read)
664 rw-rw-r– files (owner can read/write, group read/write, public read)
666 rw-rw-rw- files (owner can read/write, group read/write, public read/write)
700 rwx—— programs and directories (Owner r/w/execute)
750 rwxr-x— programs and directories etc
755 rwxr-xr-x programs and directories etc
777 rwxrwxrwx programs and directories etc