crealf - Linux
Overview
crealf
(Create Real File) converts a virtual file in a Linux cgroup to a real file on disk. This allows access to files in cgroups from outside the container.
Syntax
crealf [-f] [-d DIR] [-m MODE] [-g ID] [-u ID] FILE
Options/Flags
- -f: Force overwrite of existing file.
- -d DIR: Path to store the file. Defaults to the current working directory.
- -m MODE: File permissions (in octal). Defaults to 0644.
- -g ID: Group ID of the file. Defaults to the user’s current primary group.
- -u ID: User ID of the file. Defaults to the user’s current effective user ID.
- FILE: The virtual file to convert.
Examples
Convert a virtual file to a real file:
crealf /sys/fs/cgroup/memory/foo/memory.limit_in_bytes
Convert a virtual file to a real file in a specific directory:
crealf -d /tmp /sys/fs/cgroup/memory/foo/memory.limit_in_bytes
Common Issues
- Permission denied error: Ensure that you have root privileges or sufficient permissions to access the cgroup and the destination file.
- File not found error: Double-check the path to the virtual file and make sure that the cgroup is mounted.
Integration
crealf
can be integrated with other commands to perform advanced tasks:
- Mount cgroups: Use
mount -t cgroup cgroup MOUNTPOINT
to mount cgroups before accessing virtual files. - Chain commands: Use pipes to chain
crealf
with other commands, e.g.,crealf FILE | grep PATTERN
.
Related Commands
cgroups
: Manage control groups.mount
: Mount filesystems and cgroups.chown
: Change file ownership.