If you want to change the context of a file the chcon program. However, changes made this way will not preserved if the file is relabeled by using restorecon or using the /.autorelabel file and rebooting. The semanage program is used to make customizations to the SELinux policy configuration.
For example, if you want to set the file /path/to/myfile to have the type myfile_t, the following semanage command can be run:
# semanage fcontext -a -t myfile_t /path/to/myfile
You must be the root Linux user and in a role allowed to run semanage, such as sysadm_r or unconfined_r.
This will add an entry in the system file contexts. This entry will be persistent, even when the distribution policy is updated. However, if you change policies, e.g. from targeted to mls, you will have to re-run the above command to add it to the new policy. This can be tested by running the restorecon command and examining the file's context afterward:
# restorecon /path/to/myfile # ls -Z /path/to/myfile system_u:object_r:myfile_t /path/to/myfile