jfs_debugfs(8)

✨ jfs_debugfs — shell-type JFS file system editor ✨

Hey bestie 💖 so this is the manual page for jfs_debugfs, and yes it lives in section 8 of the manual (the sysadmin one, the main character section, obviously 👑). It's a shell-type editor for JFS file systems — like, a whole little interactive vibe where you poke at a disk at a really really low level. Buckle up 🎀

🌸 SYNOPSIS 🌸

jfs_debugfs device

🦋 DESCRIPTION 🦋

jfs_debugfs is a program which can be used to perform various low-level actions on a JFS formatted device. Like, low low. We're talking directly at the disk. It's giving surgery 🩺✨

device is the special file name corresponding to the actual device to be edited (e.g. /dev/hdb1). Yes, edited. You can literally change bytes. Iconic and terrifying 💅

jfs_debugfs must be run as root. No cap. Root only. That's not a suggestion, that's the rule, and honestly? With this much power you should be a little scared 🙈

💖 COMMANDS 💖

Here's the whole menu, every single one, no skips, no cuts, periodt 🫶

• a[lter] <block> <offset> <hex_string> — replaces the data located at the <offset> of <block> with <hex_string> 🔥
  • <block> is the block number — given in decimal
  • <offset> is the offset within that block — given in hexadecimal
  • <hex_string> is an even-numbered string of hexadecimal digits to write to the disk
• b[tree] <block> [<offset>] — * not implemented yet * 💀 displays one node of the btree located at <offset> of <block> and enters a subcommand mode to navigate the btree
  • SUBCOMMANDS:
    • l => visit left sibling
    • m => modify current node
    • p => visit parent node
    • r => visit right sibling
    • [0-9] => visit the n'th child node
    • x => exit subcommand mode
• cb[blfsck] — displays the area used by ClearBadBlockList for communication with fsck 🧹
  • SUBCOMMANDS:
    • m => modify entries
    • x => exit subcommand mode
• dir[ectory] <inode_number> [<file_set>] — displays the directory entries at <inode_number> and enters subcommand mode 📂
  • <inode_number> is the directory's inode — given in decimal
  • <file_set> currently must be zero
  • SUBCOMMANDS:
    • m => modify entries
    • x => exit subcommand mode
• d[isplay] [<block> [<offset> [<format> [<count>]]]] — displays <count> objects located at the <offset> of <block> in <format> 👀
  • <block> is the block number — given in decimal
  • <offset> is the offset within <block> — given in hexadecimal
  • <format> is one of the following:
    • a => ascii
    • b => block allocation map
    • d => decimal
    • i => inode
    • I => inode allocation map
    • s => superblock
    • x => hexadecimal
    • X => extent allocation descriptor
  • <count> is the number of objects to display — given in decimal
• dm[ap] — displays aggregate disk (block) map 🗺️
  • SUBCOMMANDS
    • m => modify map fields
    • f => display free count
    • t => display tree levels
    • x => exit subcommand mode
• dt[ree] <inode_number> [<file_set>] — displays root of the directory btree located at <inode_number> and enters a subcommand mode to navigate the btree 🌳
  • <inode_number> is the directory's inode — given in decimal
  • <file_set> currently must be zero
  • SUBCOMMANDS
    • l => visit left sibling
    • m => modify current node
    • p => visit parent node (not parent directory)
    • r => visit right sibling
    • [0-9] => visit the n'th child node
    • x => exit subcommand mode
• fsckw[sphdr] — displays the header of the fsck workspace in the aggregate 🧰
  • SUBCOMMANDS:
    • m => modify entries
    • x => exit subcommand mode
• h[elp] [<command>] — displays help for <command> 🆘 if no command is given, all possible commands are displayed
• ia[g] [<IAG_number>] [a | s | <file_set>] — displays IAG information for <IAG_number> and enters subcommand mode 🗂️
  • <IAG_number> is given in decimal
  • a is to use the primary aggregate inode table
  • s is to use the secondary aggregate inode table
  • <file_set> currently must be zero
  • SUBCOMMANDS
    • e => display/modify inode extents map
    • m => modify IAG
    • p => display/modify persistent map
    • w => display/modify working map
    • x => exit subcommand mode
• i[node] [<inode_number>] [a | s | <file_set>] — displays inode information for <inode_number> and enters subcommand mode 🔍
  • <inode_number> is given in decimal
  • a is to use the primary aggregate inode table
  • s is to use the secondary aggregate inode table
  • <file_set> currently must be zero
  • SUBCOMMANDS
    • a => display/modify inode's ACL
    • m => modify inode
    • x => exit subcommand mode
• logs[uper] — displays the journal log superblock and enters subcommand mode 📓
  • SUBCOMMANDS
    • m => modify journal log superblock
    • x => exit subcommand mode
• q[uit] — exits jfs_debugfs 👋 bye bestie!
• se[t] [<variable> <value>] — * not implemented yet * 💀 set user-defined <variable> to <value>; if no arguments are given, displays all set variables
  • <variable> must begin with an alphabetic character
• su[perblock] [p | s] — displays superblock data 🏛️
  • p displays the primary superblock
  • s displays the secondary superblock
  • SUBCOMMANDS:
    • m => modify entries
    • x => exit subcommand mode
• s2p[erblock] [p | s] — displays alternate superblock data 🏛️✨
  • p displays the primary superblock
  • s displays the secondary superblock
  • SUBCOMMANDS:
    • m => modify entries
    • x => exit subcommand mode
• u[nset] <variable> — * not implemented yet * 💀 deletes user-defined <variable>
• xt[ree] <inode_number> [<file_set>] — displays root of the non-directory btree located at <inode_number> and enters a subcommand mode to navigate the btree 🌲
  • <inode_number> is the directory's inode — given in decimal
  • <file_set> currently must be zero
  • SUBCOMMANDS
    • l => visit left sibling
    • m => modify current node
    • p => visit parent node (not parent directory)
    • r => visit right sibling
    • [0-9] => visit the n'th child node
    • x => exit subcommand mode

🐛 REPORTING BUGS 🐛

If you find a bug in JFS or jfs_debugfs, please report it via the bug tracking system ("Report Bugs" section) of the JFS project web site: http://jfs.sourceforge.net/ 🌈

Please send as much pertinent information as possible, including the complete output of running jfs_fsck with the -v and -n options on the JFS device. Like, all of it, don't be shy, the more receipts the better 🧾✨

👀 SEE ALSO 👀

jfs_fsck(8), jfs_mkfs(8), jfs_fscklog(8), jfs_logdump(8), jfs_tune(8),

💜 AUTHORS 💜

• Barry Arndt (barndt@us.ibm.com)
• William Braswell, Jr.

jfs_debugfs is maintained by IBM. See the JFS project web site for more details: http://jfs.sourceforge.net/ 🫶

okay that's the whole page, you ate that 💅 this version of the jfs_debugfs(8) manual page is dated October 29, 2002 — yeah she's an elder but she's still THAT girl — and she answers to jfs_debugfs(8). mwah, go be careful with root, ily 🎀✨🦋