In the daily management of Linux servers, disk space management is a crucial task. When the disk space is full, the system becomes unusable and can even affect the operation of applications and services. The inability to write files is one of the most common manifestations of a full disk. Whether it's the continuous growth of log files or the downloading and storage of large files, insufficient disk space will directly lead to file write failures, thus affecting normal system operation. Therefore, timely and effective handling of full disk space issues is key to ensuring the stability and availability of Linux servers.

　　When disk space is insufficient, the system will usually report a disk full problem to users or administrators. Common manifestations include the inability to create new files, the inability to write log files, or the operating system being unable to perform certain tasks. By using common command-line tools such as `df`, `du`, `ls`, and `lsof`, administrators can diagnose which directories or files in the system are consuming a large amount of disk space, thereby determining the priority and direction of handling.

　　The `df -h` command can be used to view the disk usage of each mount point in the system. This is the most direct way to check if the disk space is full. The command output will list the size, used space, available space, and mount point of each partition. For example:

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        50G   49G     0 100% /
tmpfs             2G  200M   1.8G  10% /tmp
/dev/sdb1        100G  30G  65G   32% /data

　　This output shows that the root partition /dev/sda1 is almost full, occupying 100% of its space. This indicates that the disk space for this partition is full and immediate action is needed to resolve the issue.

　　Checking Disk Space Usage

　　Once the disk space is full, the first step is to check which specific directory or file is consuming a large amount of space. The `du` command can be used to view the disk usage of each directory layer by layer, helping to pinpoint the problem. For example, using `du -sh /*` can view the space usage of each subdirectory under the root directory, with the following output:

1.2G    /bin
5.6G    /usr
2.5G    /var
100M    /home

　　This output shows that `/usr` and `/var` occupy relatively large amounts of disk space, while `/home` and `/bin` occupy relatively small amounts. For systems with full disk space, pay special attention to the `/var` directory, as system logs and cache files are typically stored here.

　　Clean Up Log Files

　　The continuous growth of log files is a common cause of disk space exhaustion. System logs, application logs, web server logs, and database logs, in particular, often consume a large amount of disk space if not cleaned regularly. By checking the `/var/log` directory, we can find that system log files, such as `syslog`, `dmesg`, and `messages`, are occupying a significant amount of space. Using `ls -lh /var/log` will list detailed information about the log files, including their size.

　　If some log files are abnormally large, you can use `logrotate` to manage them. `logrotate` is an automated log file management tool that can rotate, compress, and delete outdated log files at set intervals (such as daily, weekly, or monthly). By configuring `/etc/logrotate.conf` and related files under `/etc/logrotate.d/`, administrators can ensure that log files do not grow indefinitely. For example:

/var/log/syslog {
    weekly
    rotate 4
    compress
    missingok
    notifempty
    create 0640 root adm
}

　　This configuration will cause the `/var/log/syslog` file to be rotated weekly, retaining a maximum of four historical log files, and compressing the log files.

　　If the system no longer has enough space to store log files, outdated logs can be manually cleaned up. Use the `rm` command to delete log files that are no longer needed, such as:

rm -f /var/log/*.log

　　Cleaning Up Cache Files

　　Cache files are another common source of disk space consumption. Many programs (such as web servers, package managers, databases, etc.) store cache files in specific directories. For example, `/var/cache` and `/tmp` directories typically store cache files. Administrators can use the `du` command to check the space usage of these directories. For cache files of package managers (such as apt, yum, etc.), the corresponding commands can be used to clean them up:

　　For Debian-based systems (such as Ubuntu), the `apt-get clean` command can be used to clean up the package cache.

　　For Red Hat-based systems (such as CentOS), the `yum clean all` command can be used to clean up the cache.

　　In addition, web server cache files can also consume a lot of space, especially those of Nginx, Apache, and other proxy servers. These caches can be cleaned up periodically or configured to be automatically cleaned up when disk space is low.

　　Moving or Deleting Unnecessary Files

　　After checking and cleaning up logs and cache files, the next step is to check other files and directories, especially those that are consuming a lot of space but are no longer needed. For example, old backup files, large media files (such as videos, images, and audio files), and installation packages often occupy a significant amount of disk space.

　　Administrators can further locate these space-consuming files by searching for large files. Use the `find` command to find files exceeding a certain size:

find / -type f -size +100M

　　This will list all files larger than 100MB. Cleaning up unnecessary files can effectively free up disk space.

　　For large files that cannot be deleted directly, consider moving them to other storage devices or uploading them to a cloud storage service.

　　Expanding Disk Space

　　If cleanup is ineffective or fails to free up enough space, another solution is to expand the disk space. In a virtualized environment, administrators can expand by resizing the virtual machine's disk. On a physical server, administrators can increase storage space by adding new hard drives or expanding existing disk partitions.

　　After expanding the disk partition, use the `fdisk` or `parted` command to repartition, and then use the `resize2fs` command to expand the file system. For example, to expand the `/dev/sda1` partition:

resize2fs /dev/sda1

　　After the expansion is complete, use `df -h` to check if the new disk space has been successfully added.

　　Monitoring Disk Usage

　　To avoid similar problems in the future, administrators should regularly monitor disk space usage. Tools like `df` and `du` can be used to periodically check the disk usage of each directory. Additionally, disk space monitoring tools (such as Nagios, Zabbix, Prometheus, etc.) can be configured to promptly obtain alerts about disk space usage.

　　A full hard drive is a common problem in Linux systems, especially on long-running servers. Administrators can effectively free up disk space by cleaning up log files, cache files, and unnecessary files. If cleaning is insufficient, adding disk space or expanding partitions are also viable solutions. Furthermore, regularly monitoring disk space and properly planning disk resources can help administrators avoid insufficient disk space and ensure the long-term stable operation of the system.