crontab: command not found

Linux filesystems can report "no space left on device" for Crontab Command Not Found even when df -h shows available disk space. This happens when the inode table is exhausted — every file and directory consumes one inode, and the filesystem runs out of inodes before running out of blocks. Check both with df -h (disk space) and df -i (inodes). If df -i shows IUse% at 100%, the fix is to delete small files that are consuming inodes — often log files, temporary files, or mail spools. Docker stores each layer as separate files and can exhaust inodes rapidly. Find which directory has the most files with find / -xdev -type f | cut -d'/' -f2-3 | sort | uniq -c | sort -rn | head. Disk quotas are a second hidden cause: even if the filesystem has space, user-level quotas enforce per-user limits. Check quotas with quota -v. For LVM setups, logical volumes can be extended online with lvextend and resize2fs without unmounting.