CernVM-FS Parameters

Client parameters

Parameters recognized in configuration files under /etc/cvmfs:

Parameter Meaning
CVMFS_ALIEN_CACHE If set, use an alien cache at the given location
If set to yes, use alternative root catalog path.
Only required for fixed catalogs (tag / hash) under the alternative path.
CVMFS_AUTO_UPDATE If set to no, disables the automatic update of file catalogs.
CVMFS_AUTHZ_HELPER Full path to an authz helper, overwrites the helper hint in the catalog.
CVMFS_AUTHZ_SEARCH_PATH Full path to the directory that contains the authz helpers.
CVMFS_BACKOFF_INIT Seconds for the maximum initial backoff when retrying to download data.
CVMFS_BACKOFF_MAX Maximum backoff in seconds when retrying to download data.
Try to release pinned catalogs when their number surpasses the given watermark.
Defaults to 1/4 CVMFS_NFILES; explicitly set by shrinkwrap.
CVMFS_CACHE_BASE Location (directory) of the CernVM-FS cache.
CVMFS_CHECK_PERMISSIONS If set to no, disable checking of file ownership and permissions (open all files).
CVMFS_CLAIM_OWNERSHIP If set to yes, allows CernVM-FS to claim ownership of files and directories.
CVMFS_DEBUGLOG If set, run CernVM-FS in debug mode and write a verbose log the the specified file.
The default domain will be automatically appended to repository names
when given without a domain.
Minimum effective TTL in seconds for DNS queries of proxy server names
(not Stratum 1s). Defaults to 1 minute.
Maximum effective TTL in seconds for DNS queries of proxy server names
(not Stratum 1s). Defaults to 1 day.
CVMFS_DNS_RETRIES Number of retries when resolving proxy names
CVMFS_DNS_TIMEOUT Timeout in seconds when resolving proxy names
CVMFS_DNS_ROAMING If true, watch /etc/resolv.conf for nameserver changes
Enforce POSIX ACLs stored in the repository. Requires libfuse 3.
List of HTTP proxies similar to CVMFS_EXTERNAL_HTTP_PROXY.
The fallback proxies are added to the end of the normal proxies,
and disable DIRECT connections.
CVMFS_EXTERNAL_HTTP_PROXY Chain of HTTP proxy groups to be used when CernVM-FS is accessing external data
CVMFS_EXTERNAL_TIMEOUT Timeout in seconds for HTTP requests to an external-data server with a proxy server
CVMFS_EXTERNAL_TIMEOUT_DIRECT Timeout in seconds for HTTP requests to an external-data server without a proxy server
CVMFS_EXTERNAL_URL Semicolon-separated chain of webservers serving external data chunks.
List of HTTP proxies similar to CVMFS_HTTP_PROXY. The fallback proxies are
added to the end of the normal proxies, and disable DIRECT connections.
CVMFS_FOLLOW_REDIRECTS When set to yes, follow up to 4 HTTP redirects in requests.
CVMFS_HIDE_MAGIC_XATTRS If set to yes the client will not expose CernVM-FS specific extended attributes
Chain of HTTP proxy groups used by CernVM-FS. Necessary.
Set to DIRECT if you don’t use proxies.
CVMFS_IGNORE_SIGNATURE When set to yes, don’t verify CernVM-FS file catalog signatures.
CVMFS_INITIAL_GENERATION Initial inode generation. Used for testing.
When set to true gather performance statistics about the FUSE callbacks.
The results are displayed with cvmfs_talk internal affairs.
CVMFS_NFS_INTERLEAVED_INODES In NFS mode, use only inodes of the form \(an+b\), specified as “b%a”.
CVMFS_IPFAMILY_PREFER Which IP protocol to prefer when connecting to proxies. Can be either 4 or 6.
CVMFS_KCACHE_TIMEOUT Timeout for path names and file attributes in the kernel file system buffers.
Directory containing *.pub files used as repository signing keys.
If set, this parameter has precedence over CVMFS_PUBLIC_KEY.
CVMFS_LOW_SPEED_LIMIT Minimum transfer rate a server or proxy must provide.
Limit the number of (geo sorted) stratum 1 servers for external data
that are effectively used.
Limit the number of IP addresses a proxy names resolves into.
From all registered addresses, up to the limit are randomly selected.
CVMFS_MAX_RETRIES Maximum number of retries for a given proxy/host combination.
CVMFS_MAX_SERVERS Limit the number of (geo sorted) stratum 1 servers that are effectively used.
CVMFS_MAX_TTL Maximum file catalog TTL in minutes. Can overwrite the TTL stored in the catalog.
CVMFS_MEMCACHE_SIZE Size of the CernVM-FS meta-data memory cache in Megabyte.
Mount CernVM-FS as a read/write file system. Write operations will fail
but this option can workaround faulty open() flags.
CVMFS_NFILES Maximum number of open file descriptors that can be used by the CernVM-FS process.
CVMFS_NFS_SOURCE If set to yes, act as a source for the NFS daemon (NFS export).
If set a path, used to store the NFS maps in an SQlite database,
instead of the usual LevelDB storage in the cache directory.
CVMFS_PAC_URLS Chain of URLs pointing to PAC files with HTTP proxy configuration information.
Set the Linux kernel’s out-of-memory killer priority
for the CernVM-FS client [-1000 - 1000].
Delay in seconds after which CernVM-FS will retry the primary proxy group
in case of a fail-over to another group.
CVMFS_PROXY_TEMPLATE Overwrite the default proxy template in Geo-API calls. Only needed for debugging.
CVMFS_PUBLIC_KEY Colon-separated list of repository signing keys.
CVMFS_QUOTA_LIMIT Soft-limit of the cache in Megabyte.
CVMFS_RELOAD_SOCKETS Directory of the sockets used by the CernVM-FS loader to trigger hotpatching/reloading.
Comma-separated list of fully qualified repository names
that shall be mountable under /cvmfs.
A timestamp in ISO format (e.g. 2007-03-01T13:00:00Z).
Selects the repository state as of the given date.
CVMFS_REPOSITORY_TAG Select a named repository snapshot that should be mounted instead of trunk.
CVMFS_CONFIG_REPO_REQUIRED If set to yes, no repository can be mounted unless the config repository is available.
CVMFS_ROOT_HASH Hash of the root file catalog, implies CVMFS_AUTO_UPDATE=no.
CVMFS_SEND_INFO_HEADER If set to yes, include the cvmfs path of downloaded data in HTTP headers.
CVMFS_SERVER_CACHE_MODE Enable special cache semantics for a client used as a publisher’s repository base line.
CVMFS_SERVER_URL Semicolon-separated chain of Stratum~1 servers.
CVMFS_SHARED_CACHE If set to no, makes a repository use an exclusive cache.
CVMFS_STRICT_MOUNT If set to yes, mount only repositories that are listed in CVMFS_REPOSITORIES.
CVMFS_SUID If set to yes, enable suid magic on the mounted repository. Requires mounting as root.
If set to a number between 0 and 7, uses the corresponding
LOCAL$n$ facility for syslog messages.
If set to 1 or 2, sets the syslog level for CernVM-FS messages to
LOG_DEBUG or LOG_INFO respectively.
If set to yes, modify the command line to @vmfs2 ... in order to
act as a systemd lowlevel storage manager.
CVMFS_TIMEOUT Timeout in seconds for HTTP requests with a proxy server.
CVMFS_TIMEOUT_DIRECT Timeout in seconds for HTTP requests without a proxy server.
CVMFS_TRACEFILE If set, enables the tracer and trace file system calls to the given file.
CVMFS_USE_GEOAPI Request order of Stratum 1 servers and fallback proxies via Geo-API.
CVMFS_USER Sets the gid and uid mount options. Don’t touch or overwrite.
All messages that normally are logged to syslog are re-directed to the given file.
This file can grow up to 500kB and there is one step of log rotation.
Required for $mu$CernVM.
CVMFS_WORKSPACE Set the local directory for storing special files (defaults to the cache directory).
When connecting to an HTTPS endpoints,
it will load the certificates provided by the system.

Server parameters

Parameter Meaning
CVMFS_AUFS_WARNING Set to false to silence AUFS kernel deadlock warning.
CVMFS_AUTO_GC Enables the automatic garbage collection on publish and snapshot
Date-threshold for automatic garbage collection
(For example: 3 days ago, 1 week ago, …)
Frequency of auto garbage collection, only garbage collect if last GC is
before the given threshold (For example: 1 day ago)
CVMFS_AUTO_REPAIR_MOUNTPOINT Set to true to enable automatic recovery from bogus server mount states.
CVMFS_AUTO_TAG Creates a generic revision tag for each published revision (if set to true).
Date-threshold for automatic tags, after which auto tags get removed
(For example: 4 days ago)
CVMFS_AUTOCATALOGS Enable/disable automatic catalog management using autocatalogs.
Maximum number of entries in an autocatalog to be considered overflowed.
Default value: 100000
Minimum number of entries in an autocatalog to be considered underflowed.
Default value: 1000
Desired Average size of a file chunk in bytes
Enable/disable generation of catalog bootstrapping shortcuts during publishing.
(Useful when backend directory /data is not publicly accessible)
Compression algorithm to be used during publishing
(currently either ‘default’ or ‘none’)
The CernVM-FS version that was used to create this repository
(do not change manually).
Disable checking of OverlayFS version before usage.
Set to true to cause exceeding *LIMIT variables to be fatal to a publish
instead of a warning
Set to true to keep track of the volume of garbage collected files (increases GC running time)
Set to true to mark repository to contain external data
that is served from an external HTTP server
Maximum number of megabytes for a published file, default value: 1024
Enable/disable warning through wall and grace period before forcefully
remounting a CernVM-FS repository on the release managere machine.
CVMFS_GARBAGE_COLLECTION Enables repository garbage collection
(Stratum~0 only | if set to true)
Deprecated, set to true to enable generation of whole-file objects for large files.
Log file path to track all garbage collected objects during sweeping
for bookkeeping or debugging
CVMFS_GEO_DB_FILE Path to externally updated location of geolite2 city database, or ‘None’ for no database.
CVMFS_GEO_LICENSE_KEY A license key for downloading the geolite2 city database from maxmind.
CVMFS_GID_MAP Path of a file for the mapping of file owner group ids.
Define which secure hash algorithm should be used by CernVM-FS for CAS objects
(supported are: sha1, rmd160 and shake128)
CVMFS_IGNORE_SPECIAL_FILES Set to true to skip special files during publish without aborting.
Deprecated, defaults to true
hardlinks are found. Instead automatically break the hardlinks across directories.
CVMFS_INCLUDE_XATTRS Set to true to process extended attributes
CVMFS_MAX_CHUNK_SIZE Maximal size of a file chunk in bytes (see also CVMFS_USE_FILE_CHUNKING)
CVMFS_MAXIMAL_CONCURRENT_WRITES Maximal number of concurrently processed files during publishing.
CVMFS_MIN_CHUNK_SIZE Minimal size of a file chunk in bytes (see also CVMFS_USE_FILE_CHUNKING)
Maximum thousands of files allowed in nested catalogs, default 500
Number of threads used to commit data to storage during publication.
Currently only used by the local backend.
Maximal number of concurrently downloaded files during a Stratum1 pull operation
(Stratum~1 only).
CVMFS_PUBLIC_KEY Colon-separated path to the public key file(s) or directory(ies) of the repository to be replicated. (Stratum 1 only).
Set to true to show publisher statistics on the console
Stratum1-only: Set to no to skip this repository when executing
cvmfs_server snapshot -a
CVMFS_REPOSITORY_NAME The fully qualified name of the specific repository.
CVMFS_REPOSITORY_TYPE Defines if the repository is a master copy (stratum0) or a replica (stratum1).
The frequency in seconds of client lookups for changes in the repository.
Defaults to 4 minutes.
Maximum thousands of files allowed in root catalogs, default 200
Group name for subset of repositories used with cvmfs_server snapshot -a -g.
Added with cvmfs_server add-replica -g.
Location of the upstream spooler scratch directories;
the read-only CernVM-FS moint point and copy-on-write storage reside here.
Set a custom path for the publisher statistics database
Sets the pruning interval for the publisher statistics database
CVMFS_STRATUM0 URL of the master copy (stratum0) of this specific repository.
CVMFS_STRATUM1 URL of the Stratum1 HTTP server for this specific repository.
Controls how often sync will by called by cvmfs_server operations.
Possible levels are ‘none’, ‘default’, ‘cautious’.
CVMFS_UID_MAP Path of a file for the mapping of file owner user ids.
Mount point of the union file system for copy-on-write semantics of CernVM-FS.
Here, changes to the repository are performed
Defines the union file system to be used for the repository.
(currently aufs and overlayfs are fully supported)
Publish repository statistics plots to the Stratum 0 /stats location
Upstream spooler description defining the basic upstream storage type
and configuration (see below).
CVMFS_USE_FILE_CHUNKING Allows backend to split big files into small chunks (true | false)
CVMFS_USER The user name that owns and manipulates the files inside the repository.
Set to true to enable the hidden, virtual .cvmfs/snapshots directory
containing entry points to all named tags.
CVMFS_VOMS_AUTHZ Membership requirement (e.g. VOMS authentication) to be added into the file catalogs
SQLite file path to store the statistics. Default is
/var/spool/cvmfs/<REPO_NAME>/stats.db .
CVMFS_PRINT_STATISTICS Set to true to enable statistics printing to the standard output.
CVMFS_EXTENDED_GC_STATS Set to true to count condemned bytes in the garbage collector process.
X509_CERT_BUNDLE Bundle file with CA certificates for HTTPS connections (see Large-Scale Data CernVM-FS)
Directory file with CA certificates for HTTPS connections,
defaults to /etc/grid-security/certificates (see Large-Scale Data CernVM-FS)


The format of the CVMFS_UPSTREAM_STORAGE parameter depends on the storage backend. Note that this parameter is initialized by cvmfs_server mkfs resp. cvmfs_server add-replica. The internals of the parameter are only relevant if the configuration is maintained by a configuration management system.

For the local storage backend, the parameter specifies the storage directory (to be served by Apache) and a temporary directory in the form local,<path for temporary files>,<path to storage>, e.g.


For the S3 backend, the parameter specifies a temporary directory and the location of the S3 config file in the form s3,<path for temporary files>,<repository entry URL on the S3 server>@<S3 config file>, e.g.


The gateway backend can only be used on a remote publisher (not on a stratum 1). The parameter specifies a temporary directory and the endpoint of the gateway service, e.g.


Tiered Cache Parameters

The following parameters are used to configure a tiered cache manager instance.

Parameter Meaning
CVMFS_CACHE_$name_UPPER Name of the upper layer cache instance
CVMFS_CACHE_$name_LOWER Name of the lower layer cache instance
CVMFS_CACHE_LOWER_READONLY Set to true to avoid populating the lower layer

External Cache Plugin Parameters

The following parameters are used to configure an external cache plugin as a cache manager instance.

Parameter Meaning
If the client should start the plugin, the executable and command line
parameters of the plugin, separated by comma.
CVMFS_CACHE_$name_LOCATOR The address of the socket used for communication with the plugin.

In-memory Cache Plugin Parameters

The following parameters are interpreted from the configuration file provided to the in-memory cache plugin (see Section Example).

Parameter Meaning
CVMFS_CACHE_PLUGIN_DEBUGLOG If set, run CernVM-FS in debug mode and write a verbose log the the specified file.
CVMFS_CACHE_PLUGIN_LOCATOR The address of the socket used for client communication
CVMFS_CACHE_PLUGIN_SIZE The amount of RAM in megabyte used by the plugin for caching.