rvmutl(1)

💖 rvmutl(1) 💖

maintenance utility for RVM log ✨

🌸 NAME 🌸

rvmutl — maintenance utility for RVM log 💅

🦋 SYNOPSIS 🦋

rvmutl log

rvmutl

✨ DESCRIPTION ✨

Okay bestie, so rvmutl is the maintenance utility for RVM log. Its main features are log creation and maintenance, but it also has status and statistic display commands, plus printing commands for log records. There’s even a search facility for modifications to segments. You may find rvmutl a great debugging tool. 👑

There are two ways to use rvmutl: you can supply the name of the RVM log on the command line, or you don’t supply the name on the command line but specify the log within rvmutl (see below). 🫶

rvmutl prompts for commands with a * (asterisk) prompt. Most commands have one or more parameters, which are separated by one or more spaces. Some commands have abbreviations, and these will be specified in the command section. 💅

For example, to examine the status of a RVM log (called logfile in the example), you can do:

> rvmutl
* open_log logfile
* status

Status of log:           /home/clement/linuxobj8/rvm-src/tests/logfile

  log created on:        Tue Nov  4 1997 17:31:10.244793
  log created with:      RVM Interface Version 1.3  7 Mar 1994
  (more display omitted ...)
* quit

As another example, suppose you want to create a RVM log device on the partition /dev/hdc7, of size 1 Megabyte, you can do:

> rvmutl
* i /dev/hdc7 1M
* quit

Note that in the preceding example, we use the abbreviation i for the command init_log, and we can use the unit M to stand for Megabyte. 🍓

🌈 I/O REDIRECTION 🌈

You can redirect input and output as in typical Unix shells. For example, the following command will have all display redirected to the file allrec:

* show all > allrec
*

👑 COMMANDS 👑

In the following, I will detail all the available commands: 💖

all_spec — Show all special log records. Special log records are those non-transaction records, such as wrap-around marker and segment dictionary entry. 🔍
build_seg_dict [all] [clear]
seg_dict [all] [clear] — Build the segment dictionary by scanning through the log. Segment dictionary is an in-memory structure that maps segment code to segment file. Segment code is used in each transaction range as a short hand of the segment file involved. If the all option is specified, the whole log will be scanned, otherwise the scanning will stop when one segment dictionary entry is found. If the clear option is specified, the segment dictionary will be cleared before starting the scanning process. 📖
close_log — Close the log file. 🔒
copy_log — This provides a handy way to copy an existing log to another file or partition. Since rvm logs start on different offset, depending on whether they are files or partitions, using stock Unix commands such as cp or dd sometimes is not as nice as using this command. Some meta data (such as name of log) in the log status area in the destination log will also be updated to reflect new meta data after log copying. 📋
earliest — Show the earliest transaction record in the log. ⏳
init_log [log [length]] — Initialize a log if it does not exist, or re-initialize it if it does exist. The log will have the name log and the length of data area will be length. The actual size of the log file or partition will be slightly bigger because: 1. there is a log status area (of size 3 sectors); and 2. for log used on raw partition, there will be an offset (of 16 sectors) to jump off possible disklabel of the partition.

The length parameter is specified as an integer, optionally followed by a single character size code. The following size codes are defined: K or k for kilobytes, M or m for megabytes, S or s for sectors (512 bytes), P or p for pages (which have system dependent sizes) and B or b for bytes (default).

If either parameter is not specified, init_log will prompt for the missing information.

⚠️ RVM maintains the log continuously after creation. If you are going to re-initialize an existing log, make sure the log is empty before the re-initialization, otherwise, the transaction records in the log would be lost (i.e., they would not be applied to the data segment). You can apply all transaction records to the data segments and empty the log (also known as truncate in this manual) by the recover command. You can use the command status to check whether a log is empty.

find_earliest — Print the offset of the earliest transaction record in the log. 🔎
find_tail — Print the offset of the tail of the log. 🔎
head — Print the transaction record at the head of log. (Note that there could be even earlier than the head record -- smaller record number and smaller time stamp. They are considered truncated from the log and can be overwritten upon them freely. They are still on the log just because it happens that rvm has not yet overwritten on them, and they may be useful for debugging. The command earliest prints the earliest record.) 👀
log [log] [no_tail] [no_update │ update]
open_log [log] [no_tail] [no_update │ update] — Open the rvm log named log. You must open a log before you can use most of the rest commands. The optional no_tail switch turns of the search of tail of the log (for example, when the log tail is corrupted). The optional no_update and update switch controls whether update will be made on the log and segment (they turn on the rvm internal global variable rvm_no_update). 🔓
n [num]
next [num] — Print the next num records. If the optional argument num is not specified, then the next one record will be printed. ⏭️
ns [num]
next_sub_rec [num] — Print the next num sub-records. Sub-records are the individual ranges of a transaction. If the optional argument num is not specified, then the next one sub-record will be printed. ⏭️
p
peek [file] offset / [csf] — Peek on (or dump) the content of file. You must specify the argument file when you first peek or poke on a file, afterward you can omit the argument and rvmutl will continue using the current file. The argument offset determines from where the dump should start. The argument csf determines how the dump should be done, it comprises of three components: c, s and f; each of them represents the count, size, and format respectively. c is an integer and determines how many units, with size specified by s, should be dumped, and f specifies what is the dump format.

In the following two examples, the first command dumps, from offset 0, eight bytes in hexadecimal format; the second command dumps two long integers in decimal format. Note that how the same file content can be dumped into different format.

* peek 0 / 8xb
00000000000: 0x18 0000 0000 0000 0x23 0x17 0x14 0x63
* peek 0 / 2dl
00000000000:           24   1662261027

There are seven different possible sizes: b for byte, l for long, s for short, O for offset (two long integers representing the high and low order bits respectively), f for float, D for double and t for time value.

There are nine different possible formats: c for character, d for decimal, o for octal, x for hexadecimal, u for unsigned, f for float, D for double, O for offset (two long integers representing the high and low order bits respectively) and t for time value.

You may omit the arguments c, s and f, and rvmutl will use the defaults, which are 1, d (decimal) and l (long) respectively, for the three arguments respectively. 👁️

poke [file] offset / cs = val [val ... ] — Poke on (modify) the content of file. You must specify the argument file when you first peek or poke on a file, afterward you can omit the argument and rvmutl will continue using the current file. The argument offset determines from where the modification should start. The argument cs determines how the modifications should be done, it comprises of two components: c and s; each of them represents the count and size respectively. c is an integer and determines how many units, as specified by s, should be modified.

Examples:

* poke 512 / 4db = 25
* peek 512 / 8db
       512:  25  25  25  25   0   0   0   0

* poke 512 / 2xl = 25
* peek 512 / 8db
       512:  25   0   0   0  25   0   0   0

* poke 512 / 2b = 0x26 0x27
* peek 512 / 8db
       512:  38  39  38  39  25   0   0   0

* poke 512 / b = "abcde"
* peek 512 / 8db
       512:  97  98  99 100 101   0   0   0

Note that in the second example, the character x, which indicates hexadecimal format in peek, is silently ignored. To enter a hexadecimal number, you should use prefix 0x as in the third example. Note also that how a pattern is repeated by using the argument c in first and third example.

You can also enter string by using the double-quote mark (”), as in the last example. ✍️

pr [num]
prev [num] — Print the previous num records. If the optional argument num is not specified, then the previous one record will be printed. ⏮️
ps [num]
prev_sub_rec [num] — Print the previous num sub-records. Sub-records are the individual ranges of a transaction. If the optional argument num is not specified, then the previous one sub-record will be printed. ⏮️
quit — Quit rvmutl. 👋
read_status — Re-read the log status from on-disk log device (file or partition) to in-memory structure (status). Note that the command status show the content of the in-memory structure, but not the on-disk device. If you have made changes to the on-disk device, you may want to re-read them into the memory. 🔄

`monitor` [clear] [no_update │ update]

okay bestie, this one lets you stake out memory ranges and get notified whenever something touches them. You can specify memory ranges to be monitored by this command. When a memory range is monitored, there will be message printed out whenever there are modification within the range (E.g. in recover). ✨

the switch clear will clear all the monitor previous set. bye ranges 🫶
the switches no_update and update carry the usual meaning (c.f. open_log)

You will be asked, interactively, for the addresses and formats for the ranges you want to monitor, and you should use the syntax similar to poke. The following example shows how to use monitor, show monitor, as well as how recover prints out the modification. 💅

* open_log log3
* monitor update
  More ranges (y or n [n])? y

  Enter list of addresses/format, terminate with null line
:  0x200d7550/1l
:
* show monitor

Range    Address/format     Length
   1    0x200d7550/1dl          4

* recover
do_nv: data from log record 2101, range 52
  monitored range 1, 0x200d7550, length 4 matched by
  modified range 0x200d7550, length 4
  0x200d7550:    537286660

change_tree_insert: inserting entire range
  monitored range 1, 0x200d7550, length 4 matched by
  modified range 0x200d7550, length 4
  0x200d7550:    537286660

do_nv: data from log record 2101, range 51
  monitored range 1, 0x200d7550, length 4 matched by
  modified range 0x200ced40, length 8367
  0x200d7550:            0

change_tree_insert: inserting entire range
  monitored range 1, 0x200d7550, length 4 matched by
  modified range 0x200ced40, length 8367
  0x200d7550:            0

do_nv: data from log record 2101, range 50
  monitored range 1, 0x200d7550, length 4 matched by
  modified range 0x200cdcc4, length 16
  0x200d7550:            0

change_tree_insert: inserting entire range
  monitored range 1, 0x200d7550, length 4 matched by
  modified range 0x200cdcc4, length 16

`recover` [clear] [file] [no_update │ update]

Truncate the log. 🪵✂️ Truncation means applying the transaction records, that were logged on the log, to the data segment, and then reclaiming the space on the log used by those records. no cap, that's the whole vibe.

`set` [seg_dict] `field │ addr = val`

Set field (or memory location at addr) to val. There are five fields that you can set: head, tail, prev_head, prev_tail and log_start. (You can use prev head and prev tail to represent prev_head and prev_tail respectively.) 👑

Only the in-memory structure of the field is changed by this command — so if you want it to actually stick, use write_status to write the in-memory structure (status area) to disk. 💾

`s`

(that's the shortcut, iykyk — same as show)

`show`

all — all records
all_records — all records
earliest — earliest record
head — record at head of log
mods of / cs [= val]
modificationss of / cs [= val]

E.g. ✨

* show mods 0x2000005c / 8b

Record number: 40756 modifies specified range:

  Modification range:        1   Log offset:    224664
    VM address:     0x2000005c   Length:        52
    Segment code:            1   Offset:      4188
    Record length:         108   Back link:     48

  0x2000005c:  74 -107   0   0   0   0   0   0

* show mods 0x2000005c / 1b = 74

Record number: 40756 assigns specified values

  Modification range:        1   Log offset:    224664
    VM address:     0x2000005c   Length:        52
    Segment code:            1   Offset:      4188
    Record length:         108   Back link:     48

  0x2000005c:  74

* show mods 0x2000005c / 1b = 75
  -- no more records

monitor — all the range being monitored.
next — next record
next_sub_rec — next subrecord
ns — next subrecord
num — by record number
prev — previous record
previous — previous record
ps — previous subrecord
prev_sub_rec — previous subrecord
rec_number — num by record number
remaining — all remaining records
seg_dict — segment dictionary
seg_dictionary — segment dictionary
statistics — statistics of rvm activities
status — status area of the log
log_status — status area of the log
sr — current subrecord
sub_rec — currect subrecord
tail — tail record
timestamp — by record timestamp (note: no effect) 😭

`sizeof` `struct │ all`

Show the size of a the give structure struct, or size of all structure. The unit is byte. 📏

The following structure can be shown: condition, device_t (dev), dev_region_t, FLUSH_BUF_LEN, free_page_t, MAXPATHLEN, int, list_entry_t, log_t (log), log_buf_t, LOG_DEV_STATUS_SIZE, log_dev_status_t, log_seg_t, LOG_SPECIAL_IOV_MAX, LOG_SPECIAL_SIZE, log_special_t, log_status_t (status), log_wrap_t, long, MAX_READ_LEN, mem_region_t, MIN_NV_RANGE_SIZE, MIN_FLUSH_BUF_LEN, MIN_RECOVERY_BUF_LEN, MIN_TRANS_SIZE, mutex, NUM_CACHE_TYPES, NV_LOCAL_MAX, nv_range_t (nv), NV_RANGE_OVERHEAD, page_size, range_t, rec_end_t, rec_hdr_t, RECOVERY_BUF_LEN, region_t, rvm_length_t, rvm_offset_t, rvm_options_t, rvm_region_t, rvm_tid_t, rw_lock_t (rw_lock), rw_lock_mode_t, seg_t, struct_id_t, int_tid_t, timeval, trans_hdr_t, TRANS_SIZE, tree_links_t, tree_node_t, TRUNCATE, ulong, unsigned.

`status`

`log_status`

Show the log status area, which is the meta data about the log (include head offset, tail offset, space used by records, total log size, first record number, last record number, log creation time, last truncation time etc). 🎀

`sr`

`sub_rec`

Show the current subrecord. 🌸

`statistics`

Show the statistics of rvm activities. 📊

`tail`

Show the transaction record at the tail of log.

`update`

Turn on update (i.e. set to false the rvm-internal global variable rvm_no_update.) Update will not be made on the log and segment.

yes bestie, that's genuinely what it says — turn on update, and updates will not be made. the naming here is giving chaos. 🙈

`no_update`

Turn off update (i.e. set to true the rvm-internal global variable rvm_no_update.) Update will be made on the log and segment.

same energy, opposite direction. read twice, then read again. 💀

`write_status`

Write out the in-memory log status structure to the log status block on disk. 💾✨

🐛 BUGS 🐛

The command find_hole is not yet documented.
Peeking using the format or size of time value (t) does not work.
The way to poke an offset value is not yet documented.
sizeof of some structs (e.g. condition, int) wrongly displays the page size rather than the size of the structure.
The use of no_update does not quite work. Rvmutl easily crashes when the switch is used.
The exact semantic of replay command is not documented, and the command itself crashes quite easily.
The use of seg_dict in set is not yet documented.
The command show timestamp has no effect.

fr fr, all of the above are real and confirmed. tread carefully, bestie. 🫶

👑 AUTHOR 👑

Yui Wah LEE completely rewrote this man page (Nov. 1997) ✨

and that's the whole page, babe — footer says rvmutl(1), and the author credit goes back to Nov. 1997. you read the entire thing, which is honestly iconic of you. slay 💅🎀🦋

📦 where this page comes from

fedora 43: rvm-tools 1.28-2.fc43 · GPL-2.0-only
fedora 44: rvm-tools 1.28-3.fc44 · GPL-2.0-only
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-18: a language model's rewrite of the original, under its terms

rvmutl(1)

💖 rvmutl(1) 💖

🌸 NAME 🌸

🦋 SYNOPSIS 🦋

✨ DESCRIPTION ✨

🌈 I/O REDIRECTION 🌈

👑 COMMANDS 👑

monitor [clear] [no_update │ update]

recover [clear] [file] [no_update │ update]

set [seg_dict] field │ addr = val

s

show

sizeof struct │ all

status

log_status

sr

sub_rec

statistics

tail

update

no_update

write_status