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4.9.4. Multiple NFS Mounts

When mounting multiple mounts from the same NFS export, attempting to override the SELinux context of each mount with a different context, results in subsequent mount commands failing. In the following example, the NFS server has a single export, /export/, which has two subdirectories, /web/ and /database/. The following commands attempt two mounts from a single NFS export, and try to override the context for each one:
~]# mount server:/export/web /local/web -o context="system_u:object_r:httpd_sys_content_t:s0"
~]# mount server:/export/database /local/database -o context="system_u:object_r:mysqld_db_t:s0"
The second mount command fails, and the following is logged to /var/log/messages:
kernel: SELinux: mount invalid.  Same superblock, different security settings for (dev 0:15, type nfs)
To mount multiple mounts from a single NFS export, with each mount having a different context, use the -o nosharecache,context options. The following example mounts multiple mounts from a single NFS export, with a different context for each mount (allowing a single service access to each one):
~]# mount server:/export/web /local/web -o nosharecache,context="system_u:object_r:httpd_sys_content_t:s0"
~]# mount server:/export/database /local/database -o \ nosharecache,context="system_u:object_r:mysqld_db_t:s0"
In this example, server:/export/web is mounted locally to the /local/web/ directory, with all files being labeled with the httpd_sys_content_t type, allowing Apache HTTP Server access. server:/export/database is mounted locally to /local/database/, with all files being labeled with the mysqld_db_t type, allowing MariaDB access. These type changes are not written to disk.

Important

The nosharecache options allows you to mount the same subdirectory of an export multiple times with different contexts, for example, mounting /export/web/ multiple times. Do not mount the same subdirectory from an export multiple times with different contexts, as this creates an overlapping mount, where files are accessible under two different contexts.