.TH ocs-onthefly 8 "2026-05-03" "Clonezilla" "Clonezilla Manual"
.SH NAME
ocs-onthefly \- Clonezilla: on-the-fly disk or partition(s) cloning
.SH SYNOPSIS
.B ocs-onthefly
[\fIOPTION\fR]
.SH DESCRIPTION
.B ocs-onthefly
is used for "disk to disk" or "partition to partition" clone on-the-fly, either locally or over the network.
.SH OPTIONS
.TP
.B \-b, \-batch, \-\-batch, \-\-batch\-mode
Run program in batch mode (dangerous!), i.e., without any prompt or wait for confirmation.
.TP
.B \-cmf, \-\-chk\-chksum\-for\-files\-in\-dev
Do the files checksum inspection for cloned files in destination devices.
.TP
.B \-d, \-\-destination, \-\-target DEV
Specify the target device as DEV (e.g., /dev/sdb or sdb).
.TP
.B \-e1, \-\-change\-geometry NTFS\-BOOT\-PARTITION
Force to change the CHS (cylinders, heads, sectors) value of NTFS boot partition after cloning. NTFS-BOOT-PARTITION can be "auto" or a device name.
.TP
.B \-e2, \-\-load\-geometry\-from\-edd
Force to use the CHS from EDD (Enhanced Disk Device) when creating partition table by sfdisk.
.TP
.B \-r, \-\-resize\-partition
Resize the file system size to fit the partition size in the destination disk.
.TP
.B \-f, \-\-source DEV
Specify the source device as DEV (e.g., /dev/sda or sda).
.TP
.B \-g, \-\-grub\-install GRUB_PARTITION
Install grub in the MBR. GRUB_PARTITION can be "auto" or a device name.
.TP
.B \-\-net\-filter PROGRAM
Use the PROGRAM (gzip, lzop, bzip2, xz, lz4, zstd, cat) before sending partition data to netcat/nuttcp (only in network clone mode). Default is zstd.
.TP
.B \-nogui, \-\-nogui
Do not show GUI (TUI), use text only.
.TP
.B \-rescue, \-\-rescue
Turn on rescue mode, i.e., try to skip bad sectors.
.TP
.B \-rvd, \-\-rvd
Remove the NTFS volume dirty flag in source NTFS file system before cloning it.
.TP
.B \-irhr, \-\-irhr
Skip removing the Linux udev hardware records on the restored GNU/Linux.
.TP
.B \-ius, \-\-ius
Skip updating syslinux-related files on the restored GNU/Linux.
.TP
.B \-iui, \-\-iui
Skip updating initramfs file(s) on the restored GNU/Linux.
.TP
.B \-icds, \-\-ignore\-chk\-dsk\-size\-pt
Skip checking destination disk size before creating the partition table.
.TP
.B \-iefi, \-\-ignore\-update\-efi\-nvram
Skip updating boot entries in EFI NVRAM after cloning.
.TP
.B \-k, \-\-no\-sfdisk
Do NOT create partition table in boot sector in target machine.
.TP
.B \-k0
Create partition table based on the partition table from the source (default).
.TP
.B \-k1
Create partition table in the target disk proportionally.
.TP
.B \-k2
Enter command line prompt to create partition table manually before cloning.
.TP
.B \-j2, \-\-clone\-hidden\-data
Use dd to clone the image of the data between MBR (1st sector) and 1st partition.
.TP
.B \-m, \-\-no\-boot\-loader\-clone
Do NOT clone boot loader.
.TP
.B \-o, \-\-load\-geometry
Force to use the saved CHS (cylinders, heads, sectors) when using sfdisk.
.TP
.B \-q1, \-\-force\-to\-use\-dd
Force to use sector-by-sector copy (slow but works for all filesystems).
.TP
.B \-po, \-\-port PORT
Specify the netcat port (only in network clone mode).
.TP
.B \-p, \-pa, \-\-postaction ACTION
Action when cloning finishes: [choose|poweroff|reboot|true|CMD].
.TP
.B \-a, \-\-server
Specify the running machine is the network clone server.
.TP
.B \-s, \-\-source\-IP IP
Specify the source IP address (used in target client machine).
.TP
.B \-t, \-\-no\-restore\-mbr
Do NOT restore the MBR.
.TP
.B \-t1, \-\-restore\-raw\-mbr
Restore the prebuilt bootloader from syslinux (For Windows only).
.TP
.B \-t2, \-\-no\-restore\-ebr
Do NOT restore the EBR.
.TP
.B \-v, \-\-verbose
Prints verbose information.
.TP
.B \-np, \-\-net\-pipe PROGRAM
Use PROGRAM as network pipe program. Available: netcat, nuttcp.
.TP
.B \-x, \-\-interactive
Interactive mode.
.TP
.B \-bm, \-\-beginner\-mode
Run in beginner mode (shortcut for "-um beginner").
.TP
.B \-em, \-\-expert\-mode
Run in expert mode (shortcut for "-um expert").
.TP
.B \-um, \-\-user\-mode [beginner|expert]
Specify the user mode.
.TP
.B \-edio, \-\-enable\-direct\-io
Enable the direct IO mode of Partclone for NVMe SSD.
.SH EXAMPLES
1. To clone local sda to local sdb:
.IP
ocs-onthefly \-f sda \-d sdb
.PP
2. To clone sda from machine A (IP 192.168.100.1) to sda on machine B via network:
.PP
On machine A:
.IP
ocs-onthefly \-a \-f sda
.PP
On machine B:
.IP
ocs-onthefly \-s 192.168.100.1 \-d sda
.SH FILES
.TP
.I /etc/drbl/drbl-ocs.conf
The configuration file for Clonezilla.
.SH SEE ALSO
.BR ocs-sr (8),
.BR drbl-ocs (8)
.SH AUTHORS
Steven Shiau <steven _at_ clonezilla org>