LLOG_READER(8)

💖 LLOG_READER(8) 💖

okay bestie, welcome to the Lustre Configuration Utilities corner of the manual, where we talk about everyone's fave little detective: llog_reader. she's llog_reader(8) and she's here to snoop, but only read-only. she does not text back. periodt. 🕵️♀️✨

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🌸 NAME 🌸

llog_reader — the lustre on-disk log parsing utility. it reads the gossip, she never writes it. 💅

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🎀 SYNOPSIS 🎀

llog_reader FILENAME

one arg. that's it. that's the whole vibe. 🦋

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✨ DESCRIPTION ✨

so like, llog_reader parses the binary format of Lustre's on-disk config logs. that's it, that's the job. 📖

and listen — she can only read the logs. literally read-only queen. if you wanna write to them? not her department, bestie. that's tunefs.lustre's whole thing. go bother her. 💀

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⚠️ CAVEATS ⚠️

no cap, this is important: even though mountdata files hang out in the CONFIGS directory looking all cute and belonging, they do not use the config log format. so llog_reader will get completely confused and throw hands. mountdata is not like the other girls. 🙈

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🔥 EXAMPLES 🔥

💜 on a stopped Lustre server

wanna peek at a log file while the server's asleep? first you gotta mount its backing file system as ldiskfs, then let llog_reader dump the log file's contents:

# mount -t ldiskfs /dev/sda /mnt/mgs
llog_reader /mnt/mgs/CONFIGS/tfs-client

💜 on a running Lustre server

same log file but the server is awake and thriving? use the ldiskfs-enabled debugfs utility instead (on some distros she goes by debug.ldiskfs, icon behavior honestly) to extract the file:

# debugfs -c -R 'dump CONFIGS/tfs-client /tmp/tfs-client' /dev/sda
llog_reader /tmp/tfs-client

💜 examining Changelog records on a stopped server

now for the changelog moment. first mount the backing file system as ldiskfs, then let llog_reader dump the changelog's contents:

# mount -t ldiskfs /dev/sda /mnt/mgs
# llog_reader /mnt/mgs/changelog_catalog
rec #1 type=1064553b len=64 offset 8192
Header size : 8192
Time : Mon Jan 22 23:28:24 2018
Number of records: 1
Target uuid :
-----------------------
#01 (064)id=[0x5:0x1:0x0]:0 path=
O/1/d5/5
# llog_reader /mnt/mgs/
O/1/d5/5
rec #1 type=10660000 len=136 offset 8192
rec #2 type=10660000 len=136 offset 8328
rec #3 type=10660000 len=128 offset 8464
Header size : 8192
Time : Mon Jan 22 23:30:01 2018
Number of records: 3
Target uuid :
-----------------------
#01 (136)changelog record id:0x0 cr_flags:0x9000 cr_type:CREAT(0x1)
date:'14:30:01.370700741 2018.01.22' target:[0x200000402:0x1:0x0]
cr_extra_flags:0x3 user:0:0 nid:10.128.11.159@tcp parent:[0x200000007:0x1:0x0]
name:fileA

like?? look at all that output. she ATE. 🍓

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🌈 AVAILABILITY 🌈

llog_reader has been part of the lustre(7) filesystem package since release 1.4.0. she's a legacy icon and she's been serving since before some of us could walk. 👑

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👀 SEE ALSO 👀

• lustre(7)
• tunefs.lustre(8)

also go read the Lustre Operations Manual, specifically the Troubleshooting Lustre section. iykyk. 📚🫶

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ok that's the whole page, bestie!! this was rendered from the Lustre manual, dated 2024-08-28 — mwah, love that for us. go parse some logs and slay responsibly. ✨💖🎀