Troubleshoot Increasing Disk Space Usage in FXOS File System Mounted at opt_cisco_config Mount Point

Issue

The disk space usage in the opt_cisco_config mount point of the Firepower eXtensible Operating System (FXOS) is increasing:

asa# connect asa
firepower-1210CE# scope fabric-interconnect
firepower-1210CE /fabric-interconnect # show storage
 
Storage on local flash drive of fabric interconnect:
    Mount Point              Size (MBytes)    Used Percentage
    ------------------------ ---------------- ---------------
    mnt_boot                 7428             23
    opt_cisco_config         921              55 <--------
    opt_cisco_csp            352685           2
    opt_cisco_platform_logs  921              4
    usbdrive                 Nothing          Empty
    var_data_cores           37243            Empty

The file system mounted at the opt_cisco_config mount point has 921 MB of total disk space, and 55% of disk space usage.

According to the FXOS troubleshoot file, /opt/cisco/config/var/log/process_stdout.log is the largest file consuming more than 400 megabytes of disk space:

$ cd opt/cisco/config/var/log
opt/cisco/config/var/log$ ls -lSsgho
total 435M
432M -rwxrwxrwx 1 432M May 21 07:57 process_stdout.log
2.3M -rwxrwxrwx 1 2.3M May 21 07:57 cron
292K -rwxrwxrwx 1 290K May 21 07:57 lastlog
232K -rwxrwxrwx 1 229K May 21 07:56 ASAconsole.log
 72K -rwxrwxrwx 1  69K May 21 07:56 dmesg
 64K -rwxrwxrwx 1  61K May 21 07:57 wtmp-20260227
 32K -rwxrwxrwx 1  32K May 21 07:56 faillog
 20K -rwxrwxrwx 1  18K May 21 07:56 wtmp
   0 drwxrwxrwx 1 4.0K May 21 07:57 sa
4.0K -rwxrwxrwx 1 2.4K May 21 07:56 btmp-20260227
4.0K -rwxrwxrwx 1 1.6K May 21 07:56 btmp
   0 -rwxrwxrwx 1  160 May 21 07:56 postinstall.log
   0 -rwxrwxrwx 1    0 May 21 07:57 boot
   0 -rwxrwxrwx 1    0 May 21 07:57 process_stderr.log

Additionally, the size of the file increases day by day and the file is never rotated or compressed.

Environment

• Secure Firewall 1210, 1220 and 1230 running ASA software. Other platforms can also be affected.

• ASA version 9.22(2)32. Other software versions can also be affected.

Resolution

Contact TAC to apply the workaround for the Cisco bug ID CSCwu45359. The workaround requires backend CLI access and involves manually truncating the largest log files inside the /opt/cisco/config/var/log directory.

Cause

Excessive disk space usage by file /opt/cisco/config/var/log/process_stdout.log is caused by continuous loggingof these messages once a minute:

2026-05-20 10:25:07 dnsproxy[33143]:   -p <port>   UDP port nunber to listen on.  Default: 53
2026-05-20 10:25:07 dnsproxy[33143]:   -k          Use NLP addressing.  Default: use addressing
2026-05-20 10:25:09 monit[27882]: 'statserver' process is running with pid 31449
2026-05-20 10:26:07 dnsproxy[36667]: Unknown option/asa/bin/dnsproxy usage:
2026-05-20 10:26:07 dnsproxy[36667]:   -h          Print this help and terminate
2026-05-20 10:26:07 dnsproxy[36667]:   -c <file>   read DNS server info from file.  Default: /etc/sf/dnsproxy.conf
2026-05-20 10:26:07 dnsproxy[36667]:   -d <level>  debug level.  Default: 3
2026-05-20 10:26:07 dnsproxy[36667]:   -i <IP>     IPv4 address to listen on.  Default: 127.0.0.1
2026-05-20 10:26:07 dnsproxy[36667]:   -p <port>   UDP port nunber to listen on.  Default: 53
2026-05-20 10:26:07 dnsproxy[36667]:   -k          Use NLP addressing.  Default: use addressing
..
2026-05-20 10:27:07 dnsproxy[39999]: Unknown option/asa/bin/dnsproxy usage:
2026-05-20 10:27:07 dnsproxy[39999]:   -h          Print this help and terminate
2026-05-20 10:27:07 dnsproxy[39999]:   -c <file>   read DNS server info from file.  Default: /etc/sf/dnsproxy.conf
2026-05-20 10:27:07 dnsproxy[39999]:   -d <level>  debug level.  Default: 3
2026-05-20 10:27:07 dnsproxy[39999]:   -i <IP>     IPv4 address to listen on.  Default: 127.0.0.1
2026-05-20 10:27:07 dnsproxy[39999]:   -p <port>   UDP port nunber to listen on.  Default: 53
2026-05-20 10:27:07 dnsproxy[39999]:   -k          Use NLP addressing.  Default: use addressing

This excessive logging is tracked under Cisco bug ID CSCwu45359. Additionally, as part of the internal lab reproduction, it is confirmed that the file /opt/cisco/config/var/log/process_stdout.log is never rotated and compressed. The lack of rotation is tracked under Cisco bug ID CSCwu45848.

Related Content

• Cisco bug ID CSCwu45359

• Cisco bug ID CSCwu45848

• Troubleshoot Firepower File Generation Procedures