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  • 1.  Junos OS on external USB (SRX300)

    Posted 10-26-2025 15:30
    Edited by spuluka 10-28-2025 19:20

    Hello community, help my pls.

    I use an external USB flash drive for booting Junos OS in case something happens to the internal system.
    To record the system, I use the command:
    "request system snapshot media usb"
     
    Everything is fine, the system is recorded and I can run SRX from it.
    "show system snapshot media usb"
    Information for snapshot on USB (/dev/da1s1a) (primary)
    Creation date: Oct 20 11:20:42 2025
    JUNOS version on snapshot:
    junos: 23.4R2-S3.9
    Information for snapshot on USB (/dev/da1s2a) (backup)
    Creation date: Oct 20 11:27:56 2025
    JUNOS version on snapshot:
    junos: 23.4R2-S3.9
     
    Sometimes something happens with Junos OS on an external USB flash drive. When running the "show system snapshot media usb" command or other commands accessing the external USB drive the SRX go to reboot.
    After rebooting, the SRX may get stuck at db> or boot up correctly but then reboot again when running same commands.
     
    The problem can be solved by formatting the external USB drive and writing the system to it again, but after some time the problem may return.
     
    An example of an error message followed by a reboot:
    g_vfs_done():da1s2a[READ(offset=158795776, length=2048)]error = 5
    panic: umass1: Unknown state 1
    cpuid = 0
    KDB: stack backtrace:
    SP 0: not in kernel
    0+0x0 (0,0,0,0) ra 0 sz 0
    pid 41, process: udev-sched-1.1
    Uptime: 91d0h8m2s
    Dumping 208 MB: 205 201 197 193 189 185
    Dump aborted
    Automatic reboot in 15 seconds - press a key on the console to abort
    Rebooting...
    cpu_reset: Stopping other CPUs
     
    I couldn't reproduce the problem artificially. I tried powering off the SRX or reconnecting the external USB.

    Any ideas what could be causing this problem and how to fix it permanently?



    ------------------------------
    Pavel Guegan
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  • 2.  RE: Junos OS on external USB (SRX300)

    Posted 10-27-2025 04:53

    Hi!

    I hope you took the copy with "request system snapshot media usb" and not to "internal". I assume that was a typo, otherwise the USB would contain an old snapshot or no snapshot at all. In fact, "request system snapshot" is enough as "media usb" is the default for the SRX300 series.

    As for USB sticks, they obviously come in all kinds of qualities so use a good quality stick. You should not run the system on the USB stick for longer than you need but treat it as a last resort. After booting on the USB, install Junos to the internal flash with "request system snapshot media internal" or, better yet, install Junos from a file you copy to it via SFTP or similar.

    https://www.juniper.net/documentation/us/en/software/junos/junos-install-upgrade/topics/topic-map/backing-up-install-using-snapshot.html#d179e78

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  • 3.  RE: Junos OS on external USB (SRX300)

    Posted 10-29-2025 02:52
    Edited by Pavel Guegan 10-29-2025 02:56

    Hi
    Yes, that's right, I corrected the typo. I only boot the system on the external USB if something goes wrong with the main one. This happens very rarely. Most of the time, the external USB with the Junos is simply connected to the CRX but not active. And somehow, the USB system gets corrupted even when it's not active. Could something else cause this problem besides low-quality USB drives?
    What's also strange is that after formatting and re-writing, everything works fine again. I don't think the USB quality is the issue.



    ------------------------------
    Pavel Guegan
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    Original Message


  • 4.  RE: Junos OS on external USB (SRX300)

    Posted 10-27-2025 19:06

    As with many other discussions I think this one needs constant attention. I have had a couple burnt srx's. So letting this slip through the cracks, so to speak is a point of discussion. Normally if your srx starts to boot to internal, thats the story.

    You should also try this.

    request system storage cleanup



    ------------------------------
    Adrian Aguinaga
    B.S.C.M. I.T.T. Tech
    (Construction Management)
    A.A.S. I.T.T. Tech
    (Drafting & Design)
    ------------------------------



  • 5.  RE: Junos OS on external USB (SRX300)

    Posted 10-29-2025 03:09

    I have a separate syslog server configured, so almost nothing is written to the internal system, and the command clears almost nothing.

    The reason why SRX boots from an external USB is not so important.


    In my case, the problem is that SRX stops working correctly with an external USB for some unknown reason, even if that USB was inactive.



    ------------------------------
    Pavel Guegan
    ------------------------------

    Original Message