What is root squashing in NFS?
What is root squash? Root squash basically remaps the root UID from 0 to an anonymous user with no privileges (usually mouser:no group). This means that root is stripped of all privileges and is not able to read any files which are not world read, or write to any paths that are restricted.
What does no root squash mean?
No root-squash means that the root user will not be mapped to user nobody (this is normally done for security reasons) when mounting / accessing a NFS file system.
What is the difference between root squash and no_root_squash in NFS?
root_squash prevents remote root users from having superuser (root) privileges on remote NFS-mounted volumes. no_root_squash allows root user on the NFS client host to access the NFS-mounted directory with the same rights and privileges that the superuser would normally have.
What is all squash in NFS?
The “all_squash” option maps all client requests to a single anonymous uid/gid on the NFS server, negating the ability to track file access by user ID.
How do I get rid of root squash?
You can disable squashing by selecting No Root Squash in the Root squashing field of the Add NFS Client window.
You can also set one of the following default access control options for clients on the NFS files, exports, and directories:
- Metadata only.
- Metadata read-only.
How do I enable root squash?
On the File systems page, choose the file system that you want to enable root squashing on. On the file system details page, choose File system policy, and then choose Edit. The File system policy page appears. Choose Prevent root access by default* under Policy options.
What is Fsid in NFS?
fsid=num|root|uuid. NFS needs to be able to identify each filesystem that it exports. Normally it will use a UUID for the filesystem (if the filesystem has such a thing) or the device number of the device holding the filesystem (if the filesystem is stored on the device).
An NFS server can grant superuser capabilities on a shared file system on a per-host basis. To grant these privileges, use the root= hostname option to the share command. You should use this option with care.
What is No_all_squash?
no_all_squash: This is similar to no_root_squash option but applies to non-root users. Imagine, you have a shell as nobody user; checked /etc/exports file; no_all_squash option is present; check /etc/passwd file; emulate a non-root user; create a suid file as that user (by mounting using nfs).
How secure is NFS?
NFS itself is not generally considered secure – using the kerberos option as @matt suggests is one option, but your best bet if you have to use NFS is to use a secure VPN and run NFS over that – this way you at least protect the insecure filesystem from the Internet – ofcourse if someone breaches your VPN you’re …
What is Subtree_check?
If a subdirectory of a filesystem is exported, but the whole filesystem isn’t then whenever a NFS request arrives, the server must check not only that the accessed file is in the appropriate filesystem (which is easy) but also that it is in the exported tree (which is harder). This check is called the subtree_check.
What is sync option in NFS?
Most people use the synchronous option on the NFS server. For synchronous writes, the server replies to NFS clients only when the data has been written to stable storage. Many people prefer this option because they have little chance of losing data if the NFS server goes down or network connectivity is lost.
What is Nfsnobody?
According to Linux Standard Base, the nobody user is “Used by NFS”. In fact the NFS daemon is one of the few that still needs the nobody user. If the owner of a file or directory in a mounted NFS share doesn’t exist at the local system, it is replaced by the nobody user and its group.
What is Exportfs in Linux?
Description. The exportfs command makes local directories available for Network File System (NFS) clients to mount. This command is normally invoked during system startup by the /etc/rc. nfsfile and uses information in the /etc/exports file to export one or more directories, which must be specified with full path names …
What is the name of the option that disable root squashing?
Some Linux NFS servers have an option called no_root_squash which disables the default behavior of squashing the root user. Root squashing is a security feature.