canonical / canonical/multipass
Launch command fails on a long instance name
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Description
**Describe the bug**
On both the GUI and CLI, the launch command fails if the provided instance name is very long. This is because of the OS limitation on folder names.
**To Reproduce**
## 1. CLI
1. `multipass launch --name abcdjvkcwwuqdxgkvihthjhndimukwzzxwxtrjueurnbngmeptfmjydifqiivbhhgpppqnkbnvnmfgnzrhkbdzwayuadujtdcdnqvadnfpbjuxunjzfuugbnbhfvbuuaabhbpjvfnagmcxdzigfnpvfdytrzukbudqazygwhhyezkuhaxrcjdmihqiuccgqvucaynncvcekkmmvanpbbpdibftmuittdvnhvyfhuyuqzjefyjcqyqwgingtjtfwfikvqtyynmvcnmenfpavngrwtzcgncyndijtqciihcuupudenhjrqcepzxahravijivjdpjajzrznqiuukgdyxuqpecixeqbvzwufmmnxygepzujatencvmpupbmgfiejcizfdcvdzbvyiawcpnuuffyqrjdntrmeztktwfhbvvxgiuixkfnfpzqgnargdpvxdtypzfmpbggwhjwyuqjzuvhnmtcaqqbgekxjumnknczgipgdzxxnbhxgr`
2. The CLI starts downloading the image and shows an error. The full log is
```
multipass launch --name abcdjvkcwwuqdxgkvihthjhndimukwzzxwxtrjueurnbngmeptfmjydifqiivbhhgpppqnkbnvnmfgnzrhkbdzwayuadujtdcdnqvadnfpbjuxunjzfuugbnbhfvbuuaabhbpjvfnagmcxdzigfnpvfdytrzukbudqazygwhhyezkuhaxrcjdmihqiuccgqvucaynncvcekkmmvanpbbpdibftmuittdvnhvyfhuyuqzjefyjcqyqwgingtjtfwfikvqtyynmvcnmenfpavngrwtzcgncyndijtqciihcuupudenhjrqcepzxahravijivjdpjajzrznqiuukgdyxuqpecixeqbvzwufmmnxygepzujatencvmpupbmgfiejcizfdcvdzbvyiawcpnuuffyqrjdntrmeztktwfhbvvxgiuixkfnfpzqgnargdpvxdtypzfmpbggwhjwyuqjzuvhnmtcaqqbgekxjumnknczgipgdzxxnbhxg
Creating abcdjvkcwwuqdxgkvihthjhndimukwzzxwxtrjueurnbngmeptfmjydifqiivbhhgpppqnkbnvnmfgnzrhkbdzwayuadujtdcdnqvadnfpbjuxunjzfuugbnbhfvbuuaabhbpjvfnagmcxdzigfnpvfdytrzukbudqazygwhhyezkuhaxrcjdmihqiuccgqvucaynncvcekkmmvanpbbpdibftmuittdvnhvyfhuyuqzjefyjcqyqwgingtjtfwfikvqtyynmvcnmenfpavngrwtzcgncyndijtqciihcuupudenhjrqcepzxahravijivjdpjajzrznqiuukgdyxuqpecixeqbvzwufmmnxygepzujatencvmpupbmgfiejcizfdcvdzbvyiawcpnuuffyqrjdntrmeztktwfhbvvxgiuixkfnfpzqgnargdpvxdt
Verifying image: |
Preparing image for abcdjvkcwwuqdxgkvihthjhndimukwzzxwxtrjueurnbngmeptfmjydifqiivbhhgpppqnkbnvnmfgnzrhkbdzwayuadujtdcdnqvadnfpbjuxunjzfuugbnbhfvbuuaabhbpjvfnagmcxdzigfnpvfdytrzukbudqazygwhhyezkuhaxrcjdmihqiuccgqvucaynncvcekkmmvanpbbpdibftmuittdvnhvyfhuyuqzjefyjcqyqwgingtjtfwfikvqtyynmvcnmenfpavngrwtzcgncyndijtqciihcuupudenhjrqcepzxahravijivjdpjajzrznqiuukgdyxuqpecixeqbvzwufmmnxygepzujatencvmpupbmgfiejcizfdcvdzbvyiawcpnuuffyqrjdntrmeztktwfhbvvxgiuixkfnfpzq
launch failed: unable to create directory '/var/root/Library/Application Support/multipassd/qemu/vault/instances/abcdjvkcwwuqdxgkvihthjhndimukwzzxwxtrjueurnbngmeptfmjydifqiivbhhgpppqnkbnvnmfgnzrhkbdzwayuadujtdcdnqvadnfpbjuxunjzfuugbnbhfvbuuaabhbpjvfnagmcxdzigfnpvfdytrzukbudqazygwhhyezkuhaxrcjdmihqiuccgqvucaynncvcekkmmvanpbbpdibftmuittdvnhvyfhuyuqzjefyjcqyqwgingtjtfwfikvqtyynmvcnmenfpavngrwtzcgncyndijtqciihcuupudenhjrqcepzxahravijivjdpjajzrznqiuukgdyxuqpecixeqbvzwufmmnxygepzujatencvmpupbmgfiejcizfdcvdzbvyiawcpnuuffyqrjdntrmeztktwfhbvvxgiuixkfnfpzqgnargdpvxdtypzfmpbggwhjwyuqjzuvhnmtcaqqbgekxjumnknczgipgdzxxnbhxg'
````
## 2. GUI
1. The GUI starts downloading the image and shows the "launching state". The GUI also shows a black ribbon across the screen with the long name which is not a good user experience.
2. The GUI displays the error.
The error message is:
`unable to create directory '/var/root/ Library/Application Support/multipassd/ qemu/vault/instances/jvkcwwuqdxgkviht
hjhndimukwzzxwxtrjueurnbngmeptfmjydi
faiivbhhgpppqnkbnvnmfgnzrhkbdzwayu
adujtdednqvadnfpbjuxunjzfuugbnbhfvbu
uaabhbpjvfnagmoxdzigfnpvfdytrzukbudq
azygwhhyezkuhaxrcjdmihqiuccgqvucayn
ncvcekkmmvanpbbpdibftmuittdvnhvyfhu
yuązjefyjcąyqwgingtjtfwfikvątyynmvcn...`
**Expected behavior**
1. In the CLI, there should be an instant error message if the name exceeds a certain string length.
An example would be
```
multipass launch --name
launch failed: instance name too long ( chars, max )
Instance names map to filesystem directories and must fit OS limits.
Allowed: 1– chars, [a-zA-Z][a-zA-Z0-9-]*
Try: multipass launch --name
```
We can also truncate the echoed instance name in the error log to make the logs/error message readable. If you look at provided terminal logs in the previous section, they are not great design.
### Something to debate:
We could still launch an instance by truncating the long instance name to the max allowed length and issue a warning in the terminal.
```
multipass launch --name abcdjvkcwwuqdxgkvi...nbhxgr
warning: name truncated to chars → 'abcdjvkcwwuqdxgkvihthjhndimukwzzxwxtrjueurnbngmeptfmjydifqiivbh'
original was 612 chars (OS filesystem limit)
use --strict-name or --force etc to fail instead
Launched: abcdjvkcwwuqdxgkvihthjhndimukwzzxwxtrjueurnbngmeptfmjydifqiivbh
```
The tradeoff here is that the process is convenient but there is a silent collision risk if two long names share prefix
3. In the GUI, a text input validator on the name form field should have a validation check for string length.
**Additional info**
- OS: MacOS Tahoe 26.5
- CPU architecture or model: Apple M1
We also need to find out what is the max string length that is allowed by the various OS.
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Assessment
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