man > e2mmpstatus(8)

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📛 NAME

e2mmpstatus - Check MMP status of an ext4 file system

🚀 Quick Reference

Use Case	Command	Description
Check if a device is safe to mount	e2mmpstatus /dev/sda1	Exits 0 if safe, 1 if in use by another node
Print raw MMP information	e2mmpstatus -i /dev/sda1	Displays MMP block details without checking safety
Check by UUID	e2mmpstatus UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd	Same as device path, using filesystem UUID
Check by label	e2mmpstatus LABEL=root	Same as device path, using filesystem label

📝 SYNOPSIS

e2mmpstatus [-i] <file system>

⚙️ OPTIONS

🔍 -i

🖨️ prints out the MMP information rather than check it.

📖 DESCRIPTION

e2mmpstatus is used to check Multiple-Mount Protection (MMP) status of an ext4 file system with the mmp feature enabled. The specified file system can be a device name (e.g. /dev/hdc1, /dev/sdb2), or an ext4 file system label or UUID, for example UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root. By default, the e2mmpstatus program checks whether it is safe to mount the file system without taking the risk of mounting it more than once.

MMP (multiple-mount protection) is a feature that adds protection against the file system being modified simultaneously by more than one node. It is NOT safe to mount a file system when one of the following conditions is true:

1. 🛠️ e2fsck is running on the file system.
2. 🔗 the file system is in use by another node.
3. ⚠️ The MMP block is corrupted or cannot be read for some reason.

The e2mmpstatus program might wait for some time to see whether the MMP block is being updated by any node during this period. The time taken depends on how frequently the MMP block is being written by the other node.

🚪 Exit Codes

The exit code returned by e2mmpstatus is:

• 0 ✅ safe to mount the file system
• 1 ❌ MMP block indicates the file system is in use on another node and it is NOT safe to mount
• 2 ⚠️ some other failure occurred that prevents the check from properly detecting the current MMP status

📚 SEE ALSO

dumpe2fs(8), e2fsck(8), fstab(5), fsck(8)

📛 NAME 🚀 Quick Reference 📝 SYNOPSIS ⚙️ OPTIONS 📖 DESCRIPTION 🚪 Exit Codes 📚 SEE ALSO