chiucvallow(8)

💅 chiucvallow(8) — the z/VM IUCV HVC device driver page, bestie edition

okay so real talk, this is the manual page for chiucvallow (and its lil sibling lsiucvallow), living in the glamorous world of the z/VM IUCV HVC device driver. manual section 8, she's iconic, she's niche, she's gonna make you understand user ID filters. periodt. 💖

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✨ NAME ✨

lsiucvallow, chiucvallow — literally the tools that list, change, and verify your z/VM user ID filter settings. that's the whole vibe check. 🎀

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🦋 SYNOPSIS 🦋

like, here's how you use her:

lsiucvallow
chiucvallow -l|--list

chiucvallow -e|--edit  [filter]
chiucvallow -s|--set filter
chiucvallow -c|--clear

chiucvallow -V|--verify filter

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🌸 DESCRIPTION 🌸

so the chiucvallow program lists, verifies, and changes the z/VM user ID filter of the z/VM IUCV hypervisor console (HVC) device driver. that's her job. she ate. 💅

the z/VM user ID filter is basically the guest list 🎟️ — it lists the z/VM guest virtual machines (user IDs) that are permitted to establish IUCV communication paths with the z/VM IUCV HVC device driver. no invite, no entry, iykyk.

the filter list is a comma-separated list of z/VM user IDs, exactly as specified by the hvc_iucv_allow kernel parameter. a filter entry might end with an asterisk (*) to match multiple z/VM user IDs — wildcard slay. and you use chiucvallow to change the filter list at runtime. 🔥

chiucvallow works with the currently active filter, or with filter files that list each z/VM user ID on a separate line. filter files might also contain comment lines starting with '#'. so organized. so aesthetic. 🎀

you can edit and verify existing filter files, and replace the current z/VM user ID filter. yes bestie, full control.

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👑 OPTIONS 👑

• -h, --help — displays a short help text, then exits. cute lil reminder of how she works. 🫶
• -v, --version — displays the version of chiucvallow, then exits. the "who is she" option. ⭐
• -l, --list — displays the z/VM user IDs contained in the current filter.

heads up: using this parameter requires root authority. no root, no list. 😭

• -e, --edit [filter] — edit the current z/VM user ID filter. ✏️ filter specifies a filter file listing z/VM user IDs. if filter is not specified, the entries of the current z/VM user ID filter are used instead. either way, you're editing. the filter is opened temporarily in an editor program. when the editor is closed, the changed filter is verified and — if verification succeeds — the current filter is replaced. otherwise, a backup copy is saved for correcting errors. so nothing gets lost, bestie, don't panic. 🙈

using this parameter requires root authority.

• -c, --clear — clear the current z/VM user ID filter by deleting all user ID entries. ghosting the entire guest list. 💀

using this parameter requires root authority.

• -s, --set filter — replace the current filter with the filter entries specified by filter. the current filter can be replaced only after the new filter has been successfully verified. no chaotic unverified swaps here. 🔒

using this parameter requires root authority.

• -V, --verify filter — verify the z/VM user ID filter specified by filter. 🔍 the verification process checks the following rules:
  • z/VM user IDs consist of up to eight alphanumeric characters or underscores (_)
  • the total number of z/VM user IDs in the filter must not exceed 500
  • the filter size in bytes must not exceed 4095 bytes

three rules. no exceptions. the vibe check is very thorough. ✨

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🍓 FILES 🍓

• /sys/module/kernel/parameters/hvc_iucv_allow — the sysfs attribute for accessing the hvc_iucv_allow kernel parameter. use chiucvallow to modify and access this sysfs attribute. she's the main character, the file is just her stage. 🌈

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🧚 ENVIRONMENT 🧚

• EDITOR — specifies an editor program that is used for editing z/VM user ID filters. if EDITOR is not set or empty, vi(1) is used. so set your fave or get default vi, no cap. 💜

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⭐ SEE ALSO ⭐

• hvc_iucv(9)
• Linux on System z - Device Drivers, Features, and Commands

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and that's the whole page, bestie — go forth and filter those user IDs responsibly. mwah. 💋

sign-off ✨: this gorgeous little manpage comes from s390-tools, dated March 2015. vintage but make it iconic. 🎀